全 文 :蛋白质水平解析高山嵩草对青藏高原昼夜环境的响应∗
李 雄1ꎬ2ꎬ3ꎬ 杨云强1ꎬ2ꎬ3ꎬ 杨时海3ꎬ4ꎬ 马 岚1ꎬ2ꎬ3ꎬ
孔祥翔1ꎬ2ꎬ3ꎬ 胡向阳1ꎬ2ꎬ 杨永平1ꎬ2∗∗
(1 中国科学院昆明植物研究所东亚植物多样性与生物地理学重点实验室ꎬ 昆明 650201ꎻ 2 中国科学院昆明植物
研究所中国西南野生生物种质资源库ꎬ 昆明 650201ꎻ 3 中国科学院大学ꎬ 北京 100049ꎻ
4 中国科学院青藏高原研究所ꎬ 北京 100101)
摘要: 高山嵩草 (Kobresia pygmaea) 是高寒草甸的重要建群种ꎬ 其生长发育同时受到年际、 季节和昼夜环
境变化的影响ꎬ 但目前对高山嵩草响应昼夜环境变化的研究很少ꎮ 本研究通过差异蛋白质组学的方法ꎬ 结
合抗氧化酶活性测定和蛋白质免疫印迹技术ꎬ 分析了高山嵩草在一天中每 4个小时的蛋白质表达变化ꎮ 结
果表明: 在白天的高温、 强光和紫外辐射ꎬ 以及夜里的低温等不利条件下ꎬ 高山嵩草体内的抗氧化酶、 热
休克蛋白和脱落酸代谢相关的蛋白质等能够被大量诱导表达ꎬ 从而对细胞和机体起到保护作用ꎮ 同时ꎬ 受
蛋白质调控的一些生命活动如光合作用会集中在较为适宜的时间段进行ꎮ 通过体内蛋白质表达的可塑性和
灵活性ꎬ 高山嵩草能够有效地应对短时间里环境的变化ꎮ
关键词: 高山嵩草ꎻ 青藏高原ꎻ 昼夜环境ꎻ 蛋白质组学ꎻ 抗氧化酶
中图分类号: Q 945 79 文献标志码: A 文章编号: 2095-0845(2015)02-145-12
Protein Level Analysis of Kobresia pygmaea (Cyperaceae) Response
to Diurnal Environment on the Tibetan Plateau
LI Xiong1ꎬ2ꎬ3ꎬ YANG Yun ̄qiang1ꎬ2ꎬ3ꎬ YANG Shi ̄hai3ꎬ4ꎬ MA Lan1ꎬ2ꎬ3ꎬ
KONG Xiang ̄xiang1ꎬ2ꎬ3ꎬ HU Xiang ̄yang1ꎬ2ꎬ YANG Yong ̄ping1ꎬ2∗∗
(1 Key Laboratory for Plant Diversity and Biogeography of East Asiaꎬ Kunming Institute of Botanyꎬ Chinese Academy of Sciencesꎬ
Kunming 650201ꎬ Chinaꎻ 2 Germplasm Bank of Wild Species in Southwest Chinaꎬ Kunming Institute of Botanyꎬ Chinese
Academy of Sciencesꎬ Kunming 650201ꎬ Chinaꎻ 3 University of Chinese Academy of Sciencesꎬ Beijing 100049ꎬ Chinaꎻ
4 Institute of Tibetan Plateau Researchꎬ Chinese Academy of Sciencesꎬ Beijing 100101ꎬ China)
Abstract: Kobresia pygmaea is an important constructive species of alpine meadow on the Tibetan Plateauꎻ its
growth and development is influenced by both drastic environments of seasonal or inter ̄annual replacement and diur ̄
nal cycle. For a long timeꎬ studies about K pygmaea adaption to alpine environment were mainly focused on the
long ̄term adaptation while the diurnal responses were rarely reported. In the present studyꎬ we performed compara ̄
tive proteomics approachꎬ together with antioxidant enzyme assays and western blotꎬ to analyze the variation of pro ̄
teins expression in K pygmaea every four hours from 2 a m. to 22 p m. in a dayꎬ which were collected from eleva ̄
tion of 4 800 m on the Nyainqentanglha Mountains. The results implicated that K pygmaea was subjected to time ̄pe ̄
riod abiotic environmental stressesꎬ including high temperatureꎬ intense light and ultraviolet radiation in the day and
low temperature in the night. To maintain normal life activitiesꎬ K pygmaea formed a complex set of strategies to deal
with the potential damage. These strategies at least contained the plasticity and flexibility of antioxidant systemꎬ heat
植 物 分 类 与 资 源 学 报 2015ꎬ 37 (2): 145~156
Plant Diversity and Resources DOI: 10.7677 / ynzwyj201514070
∗
∗∗
Funding: The National Natural Sciences Foundation of China (31170256) and the Major State Basic Research Development Program (2010CB951700)
Author for correspondenceꎻ E ̄mail: yangyp@mail kib ac cn
Received date: 2014-04-30ꎬ Accepted date: 2014-07-17
作者简介: 李雄 (1987-) 男ꎬ 博士研究生ꎬ 主要从事植物生理生态学和分子生物学研究ꎮ E ̄mail: lixiong@mail kib ac cn
shock proteins accumulationꎬ and abscisic acid metabolism. Meanwhileꎬ a potential way named time ̄special activi ̄
ties regulated by proteins was also used to improve efficiency of survivalꎬ which meant some important biological
processesꎬ such as energy metabolism and photosynthesisꎬ mostly occurred at more suitable time to avoid disadvanta ̄
geous periods. These results supplied more knowledge about alpine plants adaptation to extreme day and night on the
Tibetan Plateau.
Key words: Kobresia pygmaeaꎻ Tibetan Plateauꎻ Diurnal environmentꎻ Proteomicsꎻ Antioxidant enzyme
The Tibetan Plateauꎬ with a mean altitude of
more than 4 000 mꎬ is considered as roof of the world.
Because of the special geographical location and com ̄
plex terrainꎬ it becomes the sensitive area and pro ̄
moter region of climate change (Wang et al.ꎬ 2010).
With global warming and the ozone weakeningꎬ re ̄
searches about alpine plants response and adaption to
environmental factors become more focused hotspots.
In additionꎬ the Tibetan Plateau forms typical alpine
environment with large temperature change between
day and nightꎬ intense solar radiationꎬ and some oth ̄
er environmental factorsꎬ which are considered to be
harsh environment for plants (Zhang et al.ꎬ 2010).
Thereforeꎬ alpine plants growing here must have
gained special structural characteristics and physio ̄
logicalꎬ ecological adaptation tactics.
Environmental change includes long ̄term sea ̄
sonal or inter ̄annual variation and short ̄time diurnal
turnover. Alpine environments usually show more in ̄
tense and complex changes. Plantsꎬ especially at
high altitudesꎬ need to accommodate both long ̄term
and short ̄time environmental changes to complete
normal growth and development. Although the topic
of plants adaption to environment has attracted great
attentions all the timeꎬ studies were almost reflected
in the long ̄term adaptation in the wild (Annicchiari ̄
co et al.ꎬ 1995ꎻ Yang et al.ꎬ 2011ꎻ Yang et al.ꎬ
2012). The situations of plants response to diurnal
variation were mainly focused on circadian clock reg ̄
ulation to the diurnal rhythm in model plantꎬ like
Arabidopsis thalianaꎬ under laboratory conditions
(Wang and Tobinꎬ 1998ꎻ Somersꎬ 1999ꎻ Doyle et
al.ꎬ 2002ꎻ Farre et al.ꎬ 2005ꎻ Pruneda ̄Paz and
Kayꎬ 2010ꎻ Lai et al.ꎬ 2012). Howeverꎬ relevant
studies were lack of verification in natural fieldꎬ not
to mention the Tibetan Plateau.
Alpine meadowꎬ one widely distributed vegeta ̄
tion type on Tibetan Plateauꎬ is the product of al ̄
pine climate. In alpine meadowꎬ Kobresia pygmaeaꎬ
a member of sedge familyꎬ often acts as the con ̄
structive speciesꎬ which is mainly propagated by
vegetations because of the very low seed setting rate
and germination rate (Li et al.ꎬ 2013). K. pygmaea
plays a crucial role in maintaining the stability of the
regional ecology environmentꎬ since it has a strong
viability with many excellent featuresꎬ such as resist ̄
ance to low temperatureꎬ droughtꎬ trampling and soil
erosion (Miehe et al.ꎬ 2008). Thereforeꎬ the resear ̄
ches about how K pygmaea adapts to alpine environ ̄
ment and responds to global climate change are very
significant. At presentꎬ relevant studies were mainly
focused on the long ̄term adaptation primarily from
the morphological structure (Yang et al.ꎬ 2011) and
physiological aspects (Yang et al.ꎬ 2012)ꎬ but the
response to diurnal environmental change has rarely
been reported. In this studyꎬ we adopted compara ̄
tive proteomics approachꎬ together with antioxidant
enzyme activity assays and western blot to analyze
the variations of proteins expression of K pygmaea in
a day. The results can deepen our understanding al ̄
pine plants adaptation to extreme day and night on
the Tibetan Plateau.
1 Material and methods
1 1 Samples collection
This study was conducted in Julyꎬ 2012ꎬ on the
south ̄facing slope of the Nyainqentanglha Mountains
on altitude of 4 800 m (30°31′53″ Nꎬ 91°03′18″ E)
near Damxung City in central Tibetan Plateau. To
analyze internal response of K pygmaea to external
641 植 物 分 类 与 资 源 学 报 第 37卷
environment in a dayꎬ we collected samples at Zeit ̄
geber time (ZT) 2 (2 a m.)ꎬ ZT6 (6 a m.)ꎬ ZT10
(10 a m.)ꎬ ZT14 (14 p m.)ꎬ ZT 18 (18 p m.) and
ZT22 (22 p m.) respectively. At each time pointꎬ
100 to 200 g healthy leaves of K pygmaea from a 25 ̄
m2 region were randomly selected and immediately
frozen by liquid nitrogen for later protein extraction
and enzyme assays. The samples were collected and
the experiments were conducted in triplicate.
1 2 Detection of environmental factors
The environmental factors including tempera ̄
tureꎬ light intensityꎬ ultraviolet (UV) radiation and
atmospheric humidity at different time were observed
and measured.
1 3 Antioxidant enzyme assays
Approximately 1 g of leaves from each sample col ̄
lected at different time were homogenized in extraction
buffer (50 mmolL-1 sodium phosphate pH 7 0ꎬ 1
mmolL-1 EDTAꎬ 1 mmolL-1 DTTꎬ 1 mmolL-1
GSHꎬ 1 mmolL-1 ASAꎬ 5 mmolL-1 MgCl26H2Oꎬ
1% PVP ̄40 and 20% glycerin) as the ratio of 100
mg tissue / mL buffer. The homogenates were centri ̄
fuged at 12 000 × g for 15 min at 4 ℃ꎬ and the total
soluble protein contents in the supernatants were
measured according to the Bradford method (Barbosa
et al.ꎬ 2009). The activities of catalase (CATꎬ EC1
11 1 6)ꎬ ascorbate peroxidase (APXꎬ EC1 11 1 11)ꎬ
superoxide dismutase ( SODꎬ EC1 15 1 1)ꎬ and
glutathione reductase (GRꎬ EC1 6 4 2) were de ̄
termined as previously applied method ( Beaucham
and Fridovicꎬ 1971ꎻ Nakano and AsAdaꎬ 1981ꎻ
Varga et al.ꎬ 2012).
1 4 Protein extraction and two ̄dimensional gel
electrophoresis
Protein extraction and 2D separation was per ̄
formed according to the previous methods (Damerval
et al.ꎬ 1986)ꎬ with some modifications. Approxi ̄
mately 10-20 g leaves from each sample collected at
different time were grounded in liquid nitrogen and
total soluble proteins were extracted on ice in ace ̄
tone containing 10% trichloroacetic acid (TCA) and
0 07% DTT. The homogenates were placed at -20 ℃
for 4 h and then were centrifuged (8 000 × gꎬ 30
minꎬ 4 ℃). The resulted pellets were washed with
acetone containing 0 07% DTT at -20 ℃ for 30 min
and then centrifuged (8 000 × gꎬ 20 minꎬ 4 ℃)ꎬ
which was repeated for 3 times. The final pellets
were vacuum ̄dried and then dissolved in lysate (7 M
ureaꎬ 2 M thioureaꎬ 4% CHAPS and 60 mmolL-1
DTT) for 2 h at room temperature with intermittently
shockingꎬ and then the samples were centrifuged
(12 000 ×gꎬ 20 minꎬ 20 ℃). The supernatants were
collected for 2 ̄DE experiments with 900 μg of total
proteins by a method used previously ( Bai et al.ꎬ
2011)ꎬ which were executed in triplicate.
1 5 Spots digestion and protein identification
for Mass Spectrometry analyses
Protein spots that showed significant changes in
expression with change in elevation were excised
manually from colloidal CBB ̄stained 2 ̄DE gels. Pro ̄
tein digestion with trypsin was first performedꎻ then
mass spectrometry analyses were conducted using a
MALDI ̄TOF / TOF mass spectrometer 4 800 ̄plus Prot ̄
eomics Analyzer (Applied Biosystemsꎬ Farmingtonꎬ
MAꎬ USA) according to methods previously described
(Bai et al.ꎬ 2011).
1 6 Database search
The primary and secondary MS data were trans ̄
ferred into Excel files and used as inputs to search a ̄
gainst an NCBI non ̄redundant databaseꎻ the search
was restricted to viridiplantae (green plants) using the
MASCOT search engine (www matrixscience com).
The search parameters were established as follows:
no restriction of protein molecular weightꎻ one
missed trypsin cleavage allowedꎻ cysteine treated by
iodoacetamideꎻ and oxidation of methionine. The
peptide tolerance was 100 ppm and the MS / MS tol ̄
erance was 0 25 kD. Protein identifications were val ̄
idated manuallyꎬ with at least four peptides matc ̄
hing. The keratin contamination was removed and
the MOWSE score threshold was greater than 40
(P < 0 05). Only significant hits were accepted for
the identification of the protein sample based on
MASCOT probability analysis.
7412期 LI Xiong et al.: Protein Level Analysis of Kobresia pygmaea (Cyperaceae) Response to Diurnal
1 7 Western blot analysis
SDS ̄PAGE injected with equal amount of total
protein was performed as a reference to previous
method (Laemmli et al.ꎬ 1970) using 12% polyac ̄
rylamide slab gels. Protein samples were electroblot ̄
ted onto polyinylidene difluoride ( PVDF) mem ̄
branes by using a Trans ̄Blot cell ( Bio ̄Rad) for
western blot analysis. After transferꎬ the membranes
were blocked for 1 h at room temperature. Mem ̄
branes were probed with the appropriate primary an ̄
tibodies and HRP ̄conjugated goat anti ̄rabbit se ̄
condary antibody ( Promegaꎬ Madisonꎬ WI 53711ꎬ
US)ꎬ and signals were detected using an ECL kit
(GE Companyꎬ Evansvilleꎬ Indiana 47715ꎬ US).
The primary antibodies were diluted as follows: 9 ̄
cis ̄epoxycarotenoid dioxygenase (NCED) antibodyꎬ
1 ∶1000ꎻ dehydrin antibodyꎬ 1∶1000.
2 Results and discussion
2 1 Abiotic environment factors incite relation ̄
al protein expression: proteome analysis
To investigate the response of K pygmaea to di ̄
urnal environment change in protein levelꎬ we per ̄
formed 2 ̄DE to identify the whole protein accumula ̄
tion profile in K pygmaea from ZT2 to ZT22. We
performed three biological replicates and gels were
visualized by CBB staining (Fig. S1ꎬ S2ꎬ S3). After
stainingꎬ proteins were analyzed by PDQuest soft ̄
ware (Bio ̄Rad). Under stringent conditionꎬ all dif ̄
ferentially displayed proteins were unambiguously
identified by MALDI ̄TOF ̄MS / MS analysis and sear ̄
ched against the NCBI nonredundant database. In
totalꎬ comparative proteomics patterns of six different
time samples indicated that the expressions of 120
detectable proteins varied by at least 1 5 ̄fold (P <
0 05) and 60 of these protein spots were positively
identified using MALDI ̄TOF MS (Table S1). Ac ̄
cording to the NCBI annotationsꎬ the identified pro ̄
teins could be classified into six functional groups:
Oxidation reduction processesꎬ stress resistanceꎬ en ̄
ergy metabolismꎬ photosynthesisꎬ biosynthesis and
metabolism and others (Fig 1A). Among these pro ̄
tein spotsꎬ we found that the stress resistanceꎬ pho ̄
tosynthesis and oxidation reduction processes consis ̄
ted of most of the identified proteinsꎬ occupying
22%ꎬ 18% and 18% of all respectively (Fig 1A).
A hierarchical cluster analysis was conducted to cat ̄
egorize the proteins that showed differential expres ̄
sion profiles at each time (Fig 1B).
The study demonstrated that stress resistance
proteins response to coldꎬ heat or light and some
proteins involved in oxidation reduction processes
showed significant changes in expression with diurnal
cycle. In particularꎬ a group of important proteins
belonging to the antioxidant systemꎬ such as ascor ̄
bate peroxidase (spot 135) and manganese superox ̄
ide dismutase (spot 147) exhibited significant oscil ̄
lations (Fig 2ꎬ Fig 1Bꎬ C)ꎬ which exhibited grea ̄
ter expression at ZT6 or ZT14ꎬ corresponding to the
extreme values of environmental factors.
Heat shock proteins (HSPs)ꎬ well known in all
eukaryotic organismsꎬ play essential roles in various
cellular processes when plants are exposed to stress ̄
ful conditionsꎬ such as high or low temperaturesꎬ ox ̄
ygen deprivationꎬ etc. (Siaussat et al.ꎬ 2013) Un ̄
der high temperatureꎬ HSPs produced in plants can
protect organism proteins from damaging or repair
damaged proteinsꎬ indicating that induced formation
of heat shock protein make plant to acquire heat re ̄
sistance (Kato et al.ꎬ 1993). In this studyꎬ we de ̄
tected four heat shock ̄related proteins: putative
heat ̄shock protein ( spot 3)ꎬ heat shock proteinꎬ
putative (spot 8)ꎬ stromal 70 kDa heat shock ̄relat ̄
ed protein ( spot 9) and heat shock protein hsp20
(spot 173). Three of these proteins showed expres ̄
sion peak at ZT14ꎬ and the other one peaked at
ZT10 ( Fig 2ꎬ Fig 1B). The results fully demon ̄
strated that high temperature in the afternoon (Table
S1) was an unfavorable factor for K pygmaeaꎬ so
large amount of heat shock proteins were induced to
play a potential protective effect.
Light is the necessary condition of photosynthesis
for plants. In the day lightꎬ especially at ZT10ꎬ pro ̄
teins related to light harvesting or light stimulation dis ̄
841 植 物 分 类 与 资 源 学 报 第 37卷
played a higher expression (Fig 1B). It may be crucial
for the growth of K pygmaea due to volatile environ ̄
ment conditions. For exampleꎬ in the afternoonꎬ in ̄
tense light accompanied by high temperature may dis ̄
turb photosynthesis. Taken togetherꎬ proteins response
to temperature or lightꎬ the major abiotic environment
factors in diurnal cycleꎬ were incited at special time
when they became dominant factors (Table S1).
Fig 1 Functional classification and hierarchical clustering of the identified proteins
A. Functional classification of the identified proteinsꎻ B. Hierarchical clustering of the identified protein expression profiles at
different timesꎻ C. Hierarchical clustering of some important proteins mentioned in Fig 2. Different colors correspond
to the proteins’ log ̄transformed fold ̄change ratios depicted in the bar at the bottom of the figure
Fig 2 Representative 2D gel of total protein from plants at ZT14 (left) and enlarged windows (A ̄D) of gel (right) shown on left
of plants from different time. The numbers assigned to the protein spots correspond to those listed in Table S1
9412期 LI Xiong et al.: Protein Level Analysis of Kobresia pygmaea (Cyperaceae) Response to Diurnal
2 2 Expressions of functional group proteins
were aggravated at specific times of the day
Based on the functional classification of com ̄
parative proteinsꎬ we investigated the expression pat ̄
terns of group proteins with analogous function. The
number of proteins with expressing peak or trough at
each time of six functional groups was counted sepa ̄
rately ( Fig 3). Indeedꎬ nearly all groups showed
the homologous results that proteins expression were
elevated at specific times of the day and simultane ̄
ously inhibited at some other times. More specifical ̄
lyꎬ proteins involved in stress resistance mainly
peaked from ZT2 to ZT14ꎬ with significant difference
at ZT14 (Fig 3A). This illustrated that ZT2 to ZT14
was the adverse period of K pygmaeaꎬ especially at
ZT14 accompanied by high temperature and intense
radiation. Neverthelessꎬ we also found that some
resistance proteins reached trough level from ZT18
to ZT2ꎬ exhibiting significant difference at ZT2
(Fig 3A). These results manifested that some pro ̄
teins were restrained in the evening or nightꎬ while
those involved in cold resistance were stated at the
same time. Oxidation reduction processes are a set of
important courses along with the resilience reaction
of plants. Likewiseꎬ the expression of proteins relat ̄
ed to redox processes reached the maximum from
ZT2 to ZT14 and fell to the bottom from ZT18 to
ZT2. The difference was that the largest number ap ̄
peared at ZT6 and ZT18 respectively (Fig 3B). In ̄
terestinglyꎬ we observed analogous appearance on
proteins involved in energy metabolism ( Fig 3C).
Collectivelyꎬ above results suggested that these three
processesꎬ resilience reactionꎬ redox process and
energy metabolismꎬ were a series of interrelated
complex processes in K pygmaea. By doing thisꎬ the
plants can integrate information between physiologi ̄
cal metabolism and environmental change to with ̄
stand abiotic challenges.
Apart from above resultsꎬ energy metabolismꎬ
together with biosynthesis and metabolismꎬ are closely
contacted with plants photosynthesis. Proteins in ̄
volved in photosynthesis were more active in the day ̄
time (Fig 1B)ꎬ when the light and temperature was
relatively suitable. Preciselyꎬ overwhelming majority
proteins were animated at ZT10 compared with small
amount at ZT14 ( Fig 3D). This reveled not only
that maybe conditions at noon were the most suitable
for K pygmaeaꎬ but also that photosynthesis was un ̄
der suppression in the afternoon. Previous studies
have certificated that strong light ( Poulson et al.ꎬ
2006)ꎬ high temperature (Zhou et al.ꎬ 2010ꎻ Yu et
al.ꎬ 2013) and UV radiation ( Lud et al.ꎬ 2002)
obstruct photosynthesis through complex mechanismꎻ
neverthelessꎬ plants also have evolved a set of de ̄
fense mechanisms (Liu et al.ꎬ 2012). Low tempera ̄
ture is regarded as an important interference factor
for many physiological processesꎬ and photosynthesis
is one of the most obvious processes affected by low
temperature (Oquist et al.ꎬ 1993ꎻ Liu et al.ꎬ 2012).
This is why many proteins with various functions ex ̄
hibited expression trough at midnight ( Fig 3). As
photosynthesis is essential for plantsꎬ in natural en ̄
vironmentꎬ the strategic that efficient photosynthesis
concentrated in a short time is highly beneficial to
K pygmaea in the long term. Extreme expression of
proteins involved in biosynthesis and metabolism
(Fig 3E) and some other functions (Fig 3F) were
observed in each time without significant differenceꎬ
indicating participation throughout the whole day. In
summaryꎬ expressions of functional group proteins were
exacerbated at appropriate times of the day in this re ̄
search. The temporal allocation may be favorable for
K pygmaea to maintain normal physiological activities
in the complicated and changeable environment.
2 3 Antioxidant enzyme activities exhibited chan ̄
ges in volatility
Plants will produce reactive oxygen species (ROS)
when undergone aerobic metabolismꎬ e g.ꎬ photo ̄
synthesis and respiration (Apel and Hirtꎬ 2004). If
the generation of ROS is not removed timelyꎬ plants
may experience oxidative stress due to breaking the
homeostasis in cellular redox state that may eventual ̄
ly lead to cell death (Apel and Hirtꎬ 2004). Thusꎬ
plants have evolved scavenging machineries with an ̄
051 植 物 分 类 与 资 源 学 报 第 37卷
tioxidant enzymes and antioxidants to keep ROS at
physiologically permissive levels (Mittlerꎬ 2002).
Here we determined the activities of four antiox ̄
idant enzymes (CATꎬ APXꎬ SODꎬ and GR) to in ̄
vestigate the response of K pygmaea to the complex
external environment. We observed that all four en ̄
zyme activities exhibited similarly fluctuation in the
day ( Fig 4)ꎬ which peaked from ZT2 to ZT6 or
from ZT14 to ZT18 and dipped at ZT10 or ZT22. In ̄
terestinglyꎬ the results were identical to proteomics
results of antioxidant system observed above. Our re ̄
sults are consistent with previous reports that some
antioxidant enzyme activitiesꎬ such as APXꎬ GRꎬ
and SOD increased under low temperature or heat
stress (Lee and Leeꎬ 2000ꎻ Lou et al.ꎬ 2011ꎻ Liu
et al.ꎬ 2012ꎻ Yu et al.ꎬ 2013). Thusꎬ the results
suggested unfriendly abiotic environment e g.ꎬ cold
in the mid ̄nightꎬ heat and UV radiation in the after ̄
noonꎬ could induce the production of ROS in
K pygmaea. To prevent the potential threatꎬ plants
can improve corresponding antioxidant enzyme activ ̄
ities to keep ROS homeostasis.
Fig 3 The number of proteins expressing at peak or trough according to the functional classification in Fig 1A at different times
A. Stress resistanceꎻ B. Oxidation reduction processesꎻ C. Energy metabolismꎻ D. Photosynthesisꎻ
E. Biosynthesis and metabolismꎻ F. Others
1512期 LI Xiong et al.: Protein Level Analysis of Kobresia pygmaea (Cyperaceae) Response to Diurnal
Fig 4 The change of antioxidant enzyme activities in Kobresia pygmaea at different times. Different symbols indicate
significant differences between treatments (P < 0 05) according to Tukey′s test
Previous study reported that circadian clock
regulated ROS production and scavenging in Arabi ̄
dopsis thaliana (Lai et al.ꎬ 2012)ꎬ and a core feed ̄
back loop of circadian clock has been found in
plants (Wang and Tobinꎬ 1998ꎻ Alabadi et al.ꎬ
2001ꎻ Pruneda ̄Paz and Kayꎬ 2010). We hypothe ̄
sized that antioxidant enzyme activities of K pygmaea
also would be regulated by circadian clockꎬ despite
lack of appropriate mechanism. Neverthelessꎬ plants
in natural fieldꎬ especially on Qinghai ̄Tibet Plat ̄
eauꎬ may suffer sudden stress from unstable environ ̄
ment factorsꎬ resulting in irregular fluctuation of
ROS production. In the present studyꎬ we confirmed
the truth of that K pygmaea coordinated ROS meta ̄
bolic processes with the external environment to avoid
damaging the plants.
2 4 Abscisic acid and dehydrin might partici ̄
pate in a variety of physiological regulation
To detect some substances played important
roles in plant life activities from the perspective of
proteinꎬ we performed immunoblot analysis with spe ̄
cific antibodies against abscisic acid ( ABA) syn ̄
thase and dehydrin. ABA is an important plant hor ̄
mone modulating seed dormancyꎬ germinationꎬ sto ̄
ma closure and responses to abiotic stressesꎬ inclu ̄
ding low temperaturesꎬ drought and high temperature
(Fujita et al.ꎬ 2006). Its synthesis is mediated by
ABA synthasesꎬ like 9 ̄cis ̄epoxycarotenoid dioxyge ̄
nase (NCED) in plants. Dehydrinsꎬ belonging to a
multi ̄family of proteinsꎬ are present in plants and
induced by coldꎬ saltꎬ ABA and drought stress (Ko ̄
sova et al.ꎬ 2011). In the results of western blotꎬ we
found NCED was highly accumulated at ZT2ꎬ ZT6ꎬ
ZT14ꎬ ZT18 and ZT22ꎬ but with little expression at
ZT10 ( Fig 5 )ꎬ implying similar regularity about
production of ABA. Combined with environmental
changeꎬ the result signified ABA was involved in
K pygmaea resistance to coldꎬ heat and UV radia ̄
251 植 物 分 类 与 资 源 学 报 第 37卷
tion. In spite of lower expression at ZT14 compared
with ZT2ꎬ ABA was also induced in the afternoon by
heat to regulate stomas closureꎬ may be this partly
explained many proteins related to photosynthesis
were down ̄regulated. As for dehydrinsꎬ we observed
the same expression variation (Fig 5). This sugges ̄
ted dehydrins were partly induced by ABA and
played important roles in response to extreme condi ̄
tions. Overallꎬ we found the ABA synthase and de ̄
hydrin were altered with external conditionsꎬ which
insinuated they were involved in a variety of physio ̄
logical regulation. Furthermoreꎬ the fact that both
ABA synthase and dehydrin displayed minimal ex ̄
pression at ZT10 indicated this time might be the
more appropriate condition for K pygmaea as regar ̄
ded above once again.
Fig 5 The effect of environment change on the protein accumulation
of abscisic acid synthase and dehydrin for the six samples from
different time. The coomassie stained gel is included
as a protein loading control
3 Conclusions
In the present studyꎬ we investigated and dis ̄
cussed the mode of K pygmaea response to the natu ̄
ral environment during day and night in the protein
level. Several categories of proteins were particularly
noticed to show apparent volatility changes with the
ups and downs of environmental factorsꎬ which ex ̄
hibited strong plasticity and flexibility. By analyzing
the intrinsic linkꎬ we found that K pygmaea might
suffer from time period abiotic environmental stres ̄
sesꎬ including high temperatureꎬ intense light and
UV radiation in the daytime and low temperature in
the night during a diurnal cycle. To maintain normal
life activitiesꎬ K pygmaea would not stand still and
formed a complex set of strategies to fight against the
potential damage. These strategies at least contained
antioxidant systemꎬ HSPs accumulation and ABA
metabolism. In additionꎬ a lot of important activi ̄
tiesꎬ such as energy metabolism and photosynthesisꎬ
mostly occurred at more suitable time to avoid disad ̄
vantageous periodsꎬ which were designated as time ̄
special activities. Brieflyꎬ the plasticity and flexibil ̄
ity of some functional proteins was the material basis
of K pygmaea adaptation to the large diurnal envi ̄
ronmental changes. As there was little attention that
had been paid to K pygmaea at the molecular level
before (Li et al.ꎬ 2013)ꎬ our results could improve
understanding of the interaction between alpine
plants and natural environment.
References:
Alabadi Dꎬ Oyama Tꎬ Yanovsky MJ et al.ꎬ 2001. Reciprocal regula ̄
tion between TOC1 and LHY / CCA1 within the Arabidopsis diur ̄
nal clock [J] . Scienceꎬ 293: 880—883
Annicchiarico Pꎬ Bozzo Fꎬ Parente G et al.ꎬ 1995. Analysis of adap ̄
tation of grass / legume mixtures to Italian alpine and subalpine
zones through an additive main effects and multiplicative interac ̄
tion model [J] . Grass and Forage Scienceꎬ 50: 405—413
Apel Kꎬ Hirt Hꎬ 2004. Reactive oxygen species: Metabolismꎬ oxida ̄
tive stressꎬ and signal transduction [J] . Annual Review of Plant
Biologyꎬ 55: 373—399
Bai XGꎬ Yang LMꎬ Yang YQ et al.ꎬ 2011. Deciphering the protective
role of nitric oxide against salt stress at the physiological and pro ̄
teomic levels in maize [ J] . Journal of Proteome Researchꎬ 10:
4349—4364
Barbosa Hꎬ Slater NKHꎬ Marcos JCꎬ 2009. Protein quantification in
the presence of poly ( ethylene glycol) and dextran using the
Bradford method [J] . Analytical Biochemistryꎬ 395: 108—110
Beaucham Cꎬ Fridovic Iꎬ 1971. Superoxide dismutase ̄improved as ̄
says and an assay applicable to acrylamide gels [ J] . Analytical
Biochemistryꎬ 44: 276—287
Damerval Cꎬ Devienne Dꎬ Zivy M et al.ꎬ 1986. Technical improve ̄
ments in two ̄dimensional electrophoresis increase the level of ge ̄
netic ̄variation detected in wheat ̄seedling proteins [J] . Electro ̄
phoresisꎬ 7: 52—54
Doyle MRꎬ Davis SJꎬ Bastow RM et al.ꎬ 2002. The ELF4 gene con ̄
trols diurnal rhythms and flowering time in Arabidopsis thaliana
[J] . Natureꎬ 419: 74—77
Farre EMꎬ Harmer SLꎬ Harmon FG et al.ꎬ 2005. Overlapping and
distinct roles of PRR7 and PRR9 in the Arabidopsis diurnal clock
[J] . Current Biologyꎬ 15: 47—54
Fujita Mꎬ Fujita Yꎬ Noutoshi Y et al.ꎬ 2006. Crosstalk between abiot ̄
3512期 LI Xiong et al.: Protein Level Analysis of Kobresia pygmaea (Cyperaceae) Response to Diurnal
ic and biotic stress responses: a current view from the points of
convergence in the stress signaling networks [J] . Current Opinion
in Plant Biologyꎬ 9: 436—442
Kato Sꎬ Yamagishi Kꎬ Tatsuzawa F et al.ꎬ 1993. Identification of cy ̄
toplasmic and nuclear low ̄molecular ̄weight heat ̄shock proteins
in tomato fruit [J] . Plant and Cell Physiologyꎬ 34: 367—370
Kosova Kꎬ Vitamvas Pꎬ Prasil ITꎬ 2011. Expression of dehydrins in
wheat and barley under different temperatures [ J] . Plant Sci ̄
enceꎬ 180: 46—52
Laemmli UKꎬ Beguin Fꎬ Gujerkel Gꎬ 1970. A factor preventing major
head protein of bacteriophage T4 from random aggregation [ J] .
Journal of Molecular Biologyꎬ 47: 69—74
Lai AGꎬ Doherty CJꎬ Mueller ̄Roeber B et al.ꎬ 2012. DIURNAL
CLOCK ̄ASSOCIATED 1 regulates ROS homeostasis and oxidative
stress responses [J] . Proceedings of the National Academy of Sci ̄
ences of the United States of Americaꎬ 109: 17129—17134
Lee DHꎬ Lee CBꎬ 2000. Chilling stress ̄induced changes of antioxi ̄
dant enzymes in the leaves of cucumber: in gel enzyme activity
assays [J] . Plant Scienceꎬ 159: 75—85
Li Xꎬ Hu XYꎬ Yang YPꎬ 2013. Research of important forage Kobresia
pygmaea in Qinghai ̄Tibet Plateau [J] . Pruataculture & Animal
Husbandryꎬ 1: 30—39
Liu YFꎬ Qi MFꎬ Li TLꎬ 2012. Photosynthesisꎬ photoinhibitionꎬ and
antioxidant system in tomato leaves stressed by low night tempera ̄
ture and their subsequent recovery [J] . Plant Scienceꎬ 196: 8—
17
Lou Bꎬ Xu DDꎬ Xu HX et al.ꎬ 2011. Effect of high water temperature
on growthꎬ survival and antioxidant enzyme activities in the Japa ̄
nese flounder Paralichthys olivaceus [J] . African Journal of Agri ̄
cultural Researchꎬ 6: 2875—2882
Lud Dꎬ Moerdijk TCWꎬ Van de Poll WH et al.ꎬ 2002. DNA damage
and photosynthesis in Antarctic and Arctic Sanionia uncinata
(Hedw.) Loeske under ambient and enhanced levels of UV ̄B ra ̄
diation [J] . Plant Cell and Environmentꎬ 25: 1579—1589
Miehe Gꎬ Mlehe Sꎬ Kaiser K et al.ꎬ 2008. Status and dynamics of Ko ̄
bresia pygmaea ecosystem on the Tibetan plateau [ J] . Ambioꎬ
37: 272—279
Mittler Rꎬ 2002. Oxidative stressꎬ antioxidants and stress tolerance
[J] . Trends in Plant Scienceꎬ 7: 405—410
Nakano Yꎬ AsAda Kꎬ 1981. Hydrogen ̄peroxide is scavenged by a ̄
scorbate ̄specific peroxidase in spinach ̄chloroplasts [ J] . Plant
and Cell Physiologyꎬ 22: 867—880
Oquist Gꎬ Hurry VMꎬ Huner NPAꎬ 1993. Low ̄temperature effects on
Photosynthesis and correlation with freezing tolerance in spring
and winter cultivars of wheat and rye [ J] . Plant Physiologyꎬ
101: 245—250
Poulson MEꎬ Boeger MRTꎬ Donahue RAꎬ 2006. Response of photo ̄
synthesis to high light and drought for Arabidopsis thaliana grown
under a UV ̄B enhanced light regime [ J] . Photosynthesis Re ̄
searchꎬ 90: 79—90
Pruneda ̄Paz JLꎬ Kay SAꎬ 2010. An expanding universe of diurnal
networks in higher plants [ J] . Trends in Plant Scienceꎬ 15:
259—265
Siaussat Dꎬ Laparie Mꎬ Maria A et al.ꎬ 2013. Heat shock protein re ̄
sponses to salinityꎬ food deprivationꎬ and temperature in the inva ̄
sive ground beetle Merizodus soledadinus at the Kerguelen Islands
[J] . Polar Biologyꎬ 36: 201—209
Somers DEꎬ 1999. The physiology and molecular bases of the plant di ̄
urnal clock [J] . Plant Physiologyꎬ 121: 9—19
Varga Bꎬ Janda Tꎬ Laszlo E et al.ꎬ 2012. Influence of abiotic stresses
on the antioxidant enzyme activity of cereals [J] . Acta Physiolo ̄
giae Plantarumꎬ 34: 849—858
Wang Yꎬ Meng LLꎬ Yang YP et al.ꎬ 2010. Change in floral orienta ̄
tion in Anisodus luridus (Solanaceae) protects pollen grains and
facilitates development of fertilized ovules [J] . American Jour ̄
nal of Botanyꎬ 97: 1618—1624
Wang ZYꎬ Tobin EMꎬ 1998. Constitutive expression of the DIURNAL
CLOCK ASSOCIATED 1 ( CCA1 ) gene disrupts diurnal
rhythms and suppresses its own expression [ J ] . Cellꎬ 93:
1207—1217
Yang Yꎬ Wang GXꎬ Klanderud K et al.ꎬ 2011. Responses in leaf
functional traits and resource allocation of a dominant alpine
sedge (Kobresia pygmaea) to climate warming in the Qinghai ̄
Tibetan Plateau permafrost region [ J] . Plant and Soilꎬ 349:
377—387
Yang Yꎬ Wang GXꎬ Yang LD et al.ꎬ 2012. Physiological responses of
Kobresia pygmaea to warming in Qinghai ̄Tibetan Plateau perma ̄
frost region [J] . Acta Oecologica ̄International Journal of Ecolo ̄
gyꎬ 39: 109—116
Yu Cꎬ Huang SJꎬ Hu XM et al.ꎬ 2013. Changes in photosynthesisꎬ
chlorophyll fluorescenceꎬ and antioxidant enzymes of mulberry
(Morus ssp.) in response to salinity and high ̄temperature stress
[J] . Biologiaꎬ 68: 404—413
Zhang LYꎬ Turkington Rꎬ Tang Yꎬ 2010. Flowering and fruiting phe ̄
nology of 24 plant species on the north slope of Mt. Qomolangma
(Mt. Everest) [J] . Journal of Mountain Scienceꎬ 7: 45—54
Zhou HHꎬ Chen YNꎬ Li WH et al.ꎬ 2010. Photosynthesis of Populus
euphratica in relation to groundwater depths and high tempera ̄
ture in arid environmentꎬ northwest China [J]. Photosyntheticaꎬ
48: 257—268
451 植 物 分 类 与 资 源 学 报 第 37卷
Fig S1 The first set 2 ̄DE of six samples from different time
Fig S2 The second set 2 ̄DE of six samples from different time
5512期 LI Xiong et al.: Protein Level Analysis of Kobresia pygmaea (Cyperaceae) Response to Diurnal
Fig S3 The third set 2 ̄DE of six samples from different time
Table S1 The dynamic changes of environmental factors at different time when the plant samples were collected
Symbol Time Temperature / ℃ Light intensity UV radiation Atmospheric humidity
ZT2 2 a m. 5 00 / / ∗∗∗
ZT6 6 a m. 4 12 ∗ / ∗∗∗
ZT10 10 a m. 12 35 ∗∗ ∗∗ ∗∗
ZT14 14 p m. 28 50 ∗∗∗ ∗∗∗ ∗
ZT18 18 p m. 12 50 ∗∗ ∗∗ ∗∗
ZT22 22 p m. 6 50 / / ∗∗
“ / ” means no existenceꎻ “∗” means weakꎻ “∗∗” means moderateꎻ “∗∗∗” means intense
651 植 物 分 类 与 资 源 学 报 第 37卷