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Molecular and Functional Comparisons of Reactive Burst Oxygen Species Gene Family in Arabidopsis

拟南芥Rboh基因家族成员的分子和功能学比较



全 文 :拟南芥 Rboh基因家族成员的分子和功能学比较∗
孙旭东1ꎬ2∗∗ꎬ 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西南野生生物种质资源库ꎬ 昆明  650201)
摘要: 活性氧 (reactive oxygen speciesꎬ ROS) 在植物的信号转导中起着重要的作用ꎮ 它们参与了植物的生
长发育ꎬ 生物及非生物胁迫和细胞死亡等过程ꎮ 最近的研究发现呼吸爆发氧化酶 (Respiratory burst oxidase
homologuesꎬ Rboh) 是植物 ROS的主要生产者ꎮ 拟南芥 Rboh基因家族由 10个成员组成ꎬ 他们编码的蛋白
包含 6个跨膜结构域、 以及 C末端的 FAD与 NADPH亲水结构域和 N 末端的 2 个 Ca2+结合 EF 手性结构ꎮ
本文通过聚类分析发现拟南芥 Rboh基因家族成员的三个分枝具有高度的同源性ꎬ 这说明拟南芥 Rboh家族
成员间可能存在功能冗余ꎮ 利用 RT ̄PCR分析了各基因成员的时空表达特性ꎬ 并对整个家族成员的缺失突
变体进行表型分析发现ꎬ 除了 rbohC外ꎬ 都没有明显的表型变化ꎬ 这说明拟南芥 RbohC可能在植物发育过
程中具有特殊的功能ꎮ
关键词: NADPH氧化酶ꎻ 呼吸爆发氧化酶基因ꎻ 聚类分析ꎻ T ̄PCRꎻ 功能冗余
中图分类号: Q 75              文献标志码: A              文章编号: 2095-0845(2015)04-463-09
Molecular and Functional Comparisons of Reactive Burst
Oxygen Species Gene Family in Arabidopsis∗
SUN Xu ̄dong1ꎬ2∗∗ꎬ 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 China)
Abstract: Reactive oxygen species (ROS) play a key role in cell signal transduction. They are involved in the regu ̄
lation of growthꎬ developmentꎬ responses to abiotic or biotic stimuli and cell death. Recent studies identified respira ̄
tory burst oxidase homologues (RBOHs) as the key producers of ROS. The Arabidopsis genome contains 10 Rboh
genesꎬ that encode proteins with six transmembrane domains supporting two haem groupsꎬ FAD and NADPH hydro ̄
philic domains in the C ̄terminal region and two calcium ̄binding domains (EF ̄hand) in the N ̄terminal region. In
the present studyꎬ we investigated patterns of transcription systematically in Arabidopsis plants. Comparisons among
amino acid sequences of ten Rboh genes revealed high degrees of identity among entire amino acid sequences of three
groupsꎬ suggesting that some members of Rboh family might have redundant functions. With the except of rbohCꎬ
none of the loss ̄of ̄function mutants was found to display distinct phenotypesꎬ suggesting that RbohC might have a
specific function in plant development.
Key words: NADPH oxidaseꎻ Respiratory burst oxidase homologues (Rboh) genesꎻ Phylogenetic analysisꎻ RT ̄
PCRꎻ Redundant function
  NADPH oxidases of NOX family exist in eukaryotesꎬ and play essential roles in a variety of biological processꎬ
植 物 分 类 与 资 源 学 报  2015ꎬ 37 (4): 463~471
Plant Diversity and Resources                                    DOI: 10.7677 / ynzwyj201514148

∗∗
Funding: The National Natural Science Foundation of China (NSFC 31400244)
Author for correspondence
Received date: 2014-11-06ꎬ Accepted date: 2015-03-25
作者简介: 孙旭东 (1979-) 男ꎬ 博士ꎬ 助理研究员ꎬ 主要从事植物逆境发育生物学研究ꎮ E ̄mail: sunxudong@mail􀆰 kib􀆰 ac􀆰 cn
such as defenseꎬ signal transductionꎬ and hormone
synthesis. In plantꎬ NADPH oxidases were designed
as respiratory burst oxidase homologues ( Rboh ).
Rbohs are plasma membrane proteins composed of
six transmembrane domains supporting two haem
groupsꎬ C ̄termianl FAD and NADPH hydrophilic
domains and two N ̄terminal calcium ̄binding ( EF ̄
hand) domains. NADPH acts as a cytosolic electron
donor to the extracellular O2
- electron acceptorꎬ
which is reduced to O2
- via FAD and two independ ̄
ent haems (Sagi and Fluhrꎬ 2006). Rbohs genes be ̄
long to a small multigenic familyꎬ ten members in
Arabidopsis thalianaꎬ nine in rice and six in Medica ̄
go truncatulaꎬ composed of five groups of ortholo ̄
gous sequences ( Marino et al.ꎬ 2011). Although
several members of the Rboh gene family predicts a
ubiquitous role (s) in proteins of the Rboh familyꎬ
the molecular and cellular functions of all the mem ̄
bers of this family are poorly understood.
Previous studies have been reported that some
members of the Rbohs gene familyꎬ namelyꎬ AtRbo ̄
hD and AtRbohF are shown to be involved in ROS
production during pathogen infection (Torres et al.ꎬ
2002ꎻ Torres and Danglꎬ 2005ꎻ Chaouch et al.ꎬ
2012). It has already been reported that AtRbohC /
Root Hair Defectives (RHD2) is functioned in root
hair elongation (Foreman et al.ꎬ 2003). In tobaccoꎬ
NtNOX has been shown to be functioned in normal
growth of pollen tube (Potocky et al.ꎬ 2007). Rboh ̄
dependent ROS production has also been linked to
diffuse growthꎬ such as the modulation of the cell
wall loosening during seed germinationꎬ fruit ripe ̄
ning and root and hypocotyl elongation (Dunand et
al.ꎬ 2007ꎻ Muller et al.ꎬ 2009).
In rbohF mutantsꎬ bacterial growth was increas ̄
edꎬ which was accompanied by delayed and radical ̄
ly decreased SA accumulation (Chaouch et al.ꎬ 2012).
rbohF is essential for reprogramming plant metabo ̄
lism and establishing an efficient resistance response
during a susceptible interaction. Virus induced gene
silencing of NbRbohA and NbRbohB in Nicotiana
benthamiana compromised the resistance of plants a ̄
gainst the oomycete pathogen Phytophthora infestans
and also reduced cell death response of the leaves
(Yoshioka et al.ꎬ 2003). A potato (Solanum tubero ̄
sum) StrbohA is involved in the wound healing and
resistance to natural microbial infections of potato tu ̄
bers (Kumar et al.ꎬ 2007). Transient silencing of a
barley (Hordeum vulgare) geneꎬ HvRbohA decreased
the penetration efficiency of the barley powdery mil ̄
dew fungusꎬ revealing that the HvRbohA protein fa ̄
cilitates fungal accessibility and hence promotes the
development of powdery mildew (Trujillo et al.ꎬ 2006).
During initiating trans ̄differentiation of epidermal
transfer cells in Vicia faba cotyledonsꎬ two Vicia fa ̄
ba Rboh proteinsꎬ VfRbohA and VfRbohC generate
a regulatory H2O2 signatureꎬ which directly polarized
deposition of a uniform wall on which wall ingrowths
form (Andriunas et al.ꎬ 2012).
To better understand the role of Rboh gene fam ̄
ily in plant developmentꎬ we conducted a compre ̄
hensive study of this family in Arabidopsis. Hereꎬ we
report the results of the reverse transcription (RT) ̄
PCR analysesꎬ and the phenotypes of T ̄DNA inser ̄
tion mutants of each Rboh members that has not been
previously characterized. The possible roles of Rboh
gene in plant growth and development might have re ̄
dundant functions. With the except of rbohCꎬ none
of the loss ̄of ̄function mutants was found to display
distinct phenotypesꎬ suggesting that RbohC might
have a specific function in plant development.
1  Materials and Methods
1􀆰 1  Plant materials and growth conditions
The wild type Arabidopsis (Arabidopsis thaliana)
plants used in this study were the Columbia ecotype.
T ̄DNA insertion alleles rbohA (CS862368)ꎬ rbohG
(CS833090) were obtained from the Syngenta T ̄DNA
insertion collection (www.tmri.org). rbohB (dspm)ꎬ
rbohC (dspm)ꎬ rbohD (dspm)ꎬ rbohE (salk_150096)ꎬ
rbohF (salk_034674)ꎬ rbohH (salk_136917)ꎬ rbo ̄
hJ ( salk_050665) were obtained from the ABRC.
rbohI ( GK ̄H138) was obtained from GABI ̄KAT
(www.gabi ̄kat.de).
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Plants were grown on Murashige and Skoog (MS)
agar medium (http:/ / www.phytotechlab.com) or soil.
After two days at 4 ℃ in darknessꎬ plants were
transferred to growth chamber at 200 μmol m-2 sec-1
for 16 ̄h light / 8 ̄h dark day / night cycleꎬ at 20-22 ℃
constant temperature.
1􀆰 2  Genotyping
The genotype of each T ̄DNA insertion allele was
determined by PCR of genomic DNA with using the
three primers according to T ̄DNA Primer Design
(http: / / signal.salk. edu / tdnaprimers.2.html). Wild
type should get a product of about 1 000 bpsꎬ Homo ̄
zygous lines will get a band of 400 bpsꎬ heterozygous
lines will get both bands. The gene specifiv primers:
rbohA (At5g07390): csLP GTGTTTGGAGGCACT ̄
TGCTAC and csRP TTTAGCACTGAAACAGCCTCGꎻ
rbohB (At1g09090): 154Bdspm1 GAATAATGTA ̄
ATTTAGTGAATGCG and 74Bdspm11 ACAAATTC ̄
GCTAGATTCAACCATꎻ rbohC (At5g51060): 62Cds ̄
pm1 TAGCTTCTCCATGTGACCGCG and 37Cdspm11
ATCTAAAGCTAGATGCCTTAGCꎻ rbohD (At5g47910):
211Ddspm1: GTCGCCAAAGGAGGCGCCGA and 92
Ddspm11: GGATACTGATCATAGGCGTGGCTCCAꎻ
rbohE (At1g19230): salkLP GAGTTCGAGTTTCA ̄
GTCACGC and salkRP ATGCAAGTTGATGAGAC ̄
CTCGꎻ rbohF (At1g64060): 171Fdspm1 CTTCCG ̄
ATATCCTTCAACCAACTC and 212Fdspm11 CGAA ̄
GAAGATCTGGAGACGAGAꎻ rbohG ( At4g25090):
csLP TTTTTGGCGTACCACTCAAAC and csRP CA ̄
AAGAGTTTGGGTGATAGCGꎻ rbohH (At5g60010):
salkLP AGGTCTTGCAAAATGTGTTCG and salkRP
GCCGCTAAACCTAAACCAAACꎻ rbohI (At4g11230):
gabiLP AATTGGGTAAACCATTGAAACC and gabiRP
CGTGAGATCTTCTGGATCTGCꎻ rbohJ (At3g45810):
salkLP ACTTCAACATGCCAAAAATGG and salkRP
TCAAAACAATTTCTATTTTGACGG. LBb1􀆰 3 (ATT ̄
TTGCCGATTTCGGAAC) for Salk lines. LB3 (TAG ̄
CATCTGAATTTCATAACCAATCTCGATACAC) for
CS lines. dSpm1 (CTTATTTCAGTAAGAGTGTGGG ̄
GTTTTGG) for dspm lines. gabiLB: (ATAATAAC ̄
GCTGCGGACATCTACATTTT) for GABI lines. The
conditions for the PCR reactions were: 35 cycles of
30 s at 94 ℃ꎬ 30 s at 53 ℃ꎬ and 60 s at 72 ℃ .
1􀆰 3  Chromosomal locations and analysis of du ̄
plication of genes in Rboh family
The chromosomal location of each member of
the Rboh family was determined with the Chromo ̄
some Map Tool at TAIR ( http: / / www. arabidopsis.
org / jsp / ChromosomeMap / tool. jsp). The location of
each gene in relation to major chromosomal duplica ̄
tion events in the Arabidopsis genome was deter ̄
mined with tools provided at http: / / wolfe. gen. tcd.
ie / athal / dup.
1􀆰 4  RT ̄PCR
Total RNA was extracted from various tissues from
wild ̄type plants using TRizol©reagent ( Invitrogen).
For RT ̄PCR analysisꎬ cDNA was synthesized from 2
μg of total RNA with an oligodT primer and M ̄MLV
transcriptase ( Transgenꎬ China). Transcripts were
quantified by RT ̄PCR analyses using 1 / 40th of the
resulting cDNA as template. The housekeeping ACT2
gene was used as internal standard. Triplet replicates
of independent plant samples were performed. The
gene ̄specific primers used were listed below: RbohA:
CTGGCAAAGCTGCGCCGTTC and CCGCTTACGTT ̄
TTCCCTCCTCGCꎻ RbohB: CGTGGCCAAAGGCAG ̄
TGCAG and TTGCATGCAGCAAACGCGGGꎻ RbohC:
AGGTCGAGCATCAAGGCGGTG and ACTCCTGCC ̄
GGTGGTGGCTTꎻ RbohD: GCGGCCATCCACGCAC ̄
TCAA and CCGGAGACGTTATTCCGGCGꎻ RbohE:
CGCGCTCGAGCTTGTGTTCC and TCCCGGTGAT ̄
TCCTTCTGCACCTꎻ RbohF: TCACAGCCAAAGGA ̄
GCAGCTGAA and ACGAGGTCGAAGTATGTTGGC ̄
TGTꎻ RbohG: CCGACGGTAACGCTGCCTGG and
CGTCTTCCGTAAGTCTACCATCCGAꎻ RbohH: TT ̄
GAGTGCCTCGGCGAACCG and CGGCGTTCTGTA ̄
CCGCTCTGGꎻ RbohI: TGCAGACGAGTTGTTCGAC ̄
GC and TGCTCGTTCTCGCAACCTCGꎻ RbohJ: TG ̄
ACGGGAGGCTTCCCAAGGA and ACGAGCCTGT ̄
TCGCGGATGC. Every pair of primers span the ex ̄
on3 / exon5 region. PCR products were examined by
separating on a 1􀆰 5% agarose gel.
1􀆰 5  Scanning electron microscopy
Leaves of wild ̄type plants and rbohC plants
5644期      SUN Xu ̄dong et al.: Molecular and Functional Comparisons of Reactive Burst Oxygen Species Gene 􀆺     
were fixed and dehydrated as described previously
(Sun et al.ꎬ 2013). The samples were observed and
photographed under a scanning electron microscope
(SEMꎬ JSM ̄6360LV SEMꎻ JEOL Ltd.ꎬ Japan) at
an accelerating voltage of 10 kV.
1􀆰 6  GUS staining
GUS staining was performed as described previ ̄
ously (Malamy and Benfeyꎬ 1997). The samples were
examined using a Leica microscopeꎬ and images
were captured using a Leica LM1000 camera.
2  Result
2􀆰 1  Arabidopsis genome contains 10 Rboh genes
There are ten members of reactive burst oxygen
species (Rboh) genes in Arabidopsis genome. Fig􀆰 1A
shows a phylogenetic relationship between all of Ara ̄
bidopsis Rboh proteinsꎬ which was deduced with
neighbor ̄joining method. The Arabidopsis genome
contains many putative paralogs that likely arose via
segmental chromosome duplication events (Blanc et
al.ꎬ 2000ꎻ Vision et al.ꎬ 2000). We investigated a
possible relationship between the genetic divergence
of members of the Rboh family and duplication e ̄
vents in the Arabidopsis genome. We examined the
chromosomal locations and the duplicated segments
in which genes of the AtRboh family are foundꎬ u ̄
sing data from the Arabidopsis Genome Initiative
(2000) and from the report by Blanc et al. (2003)
(Fig􀆰 1B).
The AtRboh genes are distributed in four chro ̄
mosomesꎬ except chromosome 2. The search for such
paralogs within the Rboh family by the use of the
Paralogons in Arabidopsis program ( http: / / wolfe.
gen.tcd.i.e. / athal / dup) revealed that AtRbohA ̄AtR ̄
bohB ̄AtRbohCꎬ AtRbohF ̄Iꎬ and AtRbohH ̄J were loca ̄
ted in the duplicated segments (Blanc et al.ꎬ 2003)
and form paralogous gene pairsꎬ respectively. The phy ̄
logenetic tree shown in Fig􀆰 1A supports this notion.
The comparison of the predicted amino acid sequen ̄
ces of the AtRboh genes also supported this notion
Fig􀆰 1  Aꎬ The phylogenetic tree of Arabidopsis Rboh family proteins. An unrooted neighbor joining tree was generated using MEGA 6 neighbor join ̄
ing software Bootstrap values (1ꎬ000 replicates) are shown. Bar (0􀆰 05) represents 5% amino acid substitutions per site per million yearsꎻ Bꎬ Chro ̄
mosomal positions and duplication of genes in the Rboh family in Arabidopsis. Green bars and white ellipses show the chromosomes and the positions
of centromeresꎬ respectively. The chromosome number is given at the top of each chromosome. Each set of putative duplicated genes is shown in a sin ̄
gle colorꎻ Cꎬ Comparison of the predicted amino acid sequences of the rboh genes in Arabidopsis. Each number indicates the identityꎬ as a percent ̄
ageꎬ between the predicted amino acid sequendes of indicated proteinsꎬ as determined with the Maximum Matching pogram GENETYXMAC ver. 13
664                                  植 物 分 类 与 资 源 学 报                            第 37卷
(Fig􀆰 1C). The identity between AtRbohA and AtR ̄
bohC is 64􀆰 7%ꎬ AtRbohF and AtRbohI is 61􀆰 5%ꎬ
AtRbohH and AtRbohJ is even up to 83􀆰 5%. These
results suggested that members of AtRboh gene family
might be duplicated in the distant past.
2􀆰 2  Expression of AtRboh genes
We performed RT ̄PCR to examine the patterns
of expression of all AtRboh genes in a variety of Ara ̄
bidopsis tissues. In all casesꎬ primers spanning the
predicted introns were used to distinguish between
amplification of genome and amplification of cDNA.
Expression were detected in 9 genes (Fig􀆰 2).
Fig􀆰 2  RT ̄PCR analysis of the expression profiles
of Rboh genes in wild type
RLꎬ rosette leavesꎻ CLꎬ cauline leavesꎻ SHꎬ shoot tissueꎻ STꎬ inflo ̄
rescence stemꎻ BDꎬ floral budsꎻ FLꎬ open flowersꎻ SLꎬ siliquesꎻ
RTꎬ root. The former seven organ samples were prepared from
40 ̄old ̄d flowering plants. The RT was 14 ̄old ̄d seedlings
grown on Murashige and Skoog agar medium
No expression was detected for AtRbohF in any
of the tissues tested. This result indicated that the
expression patterns of AtRboh genes were quite varia ̄
bleꎬ with tissue or developmental stage ̄specific pat ̄
terns (Fig􀆰 2). Transcripts from AtRbohAꎬ AtRbohB
and AtRbohG were detected only in root. AtRbohC
transcripts were detected in flower budsꎬ open flow ̄
ers and rootsꎬ low levels were also detected in shoot.
AtRbohD transcripts were detected in all tissues ex ̄
cept cauline leaves and inflorescence stems. Where ̄
as AtRbohE transcripts were expressed predominantly
in rootsꎬ and also detected in flower budsꎬ but not in
open flower. Transcripts of AtRbohI were detected in
all tissues examinedꎬ although at variable levels.
Transcripts of both AtRbohH and AtRBOHJ were pri ̄
mary detected in flower budsꎬ but faint bands were
also amplified from open flowers.
2􀆰 3  Phenotypes of T ̄DNA insertion mutants of
the Arabidopsis Rboh genes
For functional analysis of the AtRboh gene familyꎬ
T ̄DNA insertion mutants of all AtRboh genesꎬ were ob ̄
tained from Syngentaꎬ ABRC or GABI ̄KAT (Fig􀆰 3).
Homozygous mutant plants were identified by
PCR genotyping using gene ̄specific primers (Fig􀆰 3).
All of the single mutants except for AtrbohC showed
no distinct phenotypes in terms of growth and devel ̄
opment (Fig􀆰 4).
Howeverꎬ AtrbohC showed to have lobed leaves
(Fig􀆰 5). Typicallyꎬ the Arabidopsis leaf epidermis
consists of interlocked jigsaw puzzle ̄shaped cells
with protruding lobes and indentations (Xu et al.ꎬ
2003ꎻ Fu et al.ꎬ 2005).
Since loss ̄of ̄function mutant AtrbohC affected
the leaf developmentꎬ we suspected that the epider ̄
mis cell layer in AtrbohC mutants may display a phe ̄
notype. In order to assess the effect of AtRbohC on
epidermal developmentꎬ we analyzed cell shape in
the epidermis of the leaf lamina of expanding rosette
leaves from four ̄week ̄old AtrbohC. For consistencyꎬ
a location midway up the length of the lamina and mid ̄
way between the margin and the midvein of transgenic
plants was chosen. The epidermis of WT laminae
showed jigsaw puzzle ̄shaped cells (Fig􀆰 6A). In con ̄
trastꎬ the loss ̄of ̄function AtrbohC mutants displayed
altered morphology of the leaf pavement cells. Cell
shapes were often lacking lobes and necks (Fig􀆰 6Bꎬ
Cꎬ D). Transgenic plants carrying ProRbohC ∶ GUS
were prepared to localize AtRbohC expression more
precisely. GUS staining was strong signal in the vas ̄
cular tissues of the leavesꎬ hypocotyl and roots in
two ̄week ̄old transgenic plants (Fig􀆰 7Aꎬ B).
7644期      SUN Xu ̄dong et al.: Molecular and Functional Comparisons of Reactive Burst Oxygen Species Gene 􀆺     
Fig􀆰 3  Genomics structures of the Arabidopsis Rboh genes and locations of T ̄DNA insertions and Characterization of rboh mutants by PCR.
Exons are indicated by boxesꎬ whereas introns are indicated by lines. Arrowheads indicate the T ̄DNA inserted localization
aꎬ rbohAꎻ bꎬ rbohBꎻ cꎬ rbohCꎻ dꎬ rbohDꎻ eꎬ rbohEꎻ fꎬ rbohFꎻ gꎬ rbohGꎻ hꎬ rbohHꎻ iꎬ rbohIꎻ jꎬ rbohJ.
1ꎬ homozygote mutantꎻ 2ꎬ wild typeꎻ Mꎬ DNA ladder marker
Fig􀆰 4  Phenotypes of rboh mutants in Arabidopsis
Aꎬ rbohAꎻ Bꎬ rbohBꎻ Cꎬ rbohDꎻ Dꎬ rbohEꎻ Eꎬ rbohFꎻ Fꎬ rbohGꎻ Gꎬ rbohHꎻ Hꎬ rbohIꎻ Iꎬ rbohJ. Jꎬ wild type. bar = 1 cm
864                                  植 物 分 类 与 资 源 学 报                            第 37卷
Fig􀆰 5  Leaf phenotype of rbohC mutants. bar = 0􀆰 2 cm
3  Discussion
In the present studyꎬ the transcripts of all mem ̄
bers of the AtRboh gene family accumulate at differ ̄
ent respective levels in Arabidopsis plantsꎬ and have
a variety of transcriptional profiles in the whole
plant. We also found three groupsꎬ with two or three
members eachꎬ of AtRboh proteins with high degrees
Fig􀆰 6  Scanning electron microscope analysis of rbohC abaxial lamina epidermis. bar = 50 μm
A. jigsaw puzzle ̄shaped cellsꎻ Bꎬ Cꎬ D. cell shapes of lacking lobes and necks
Fig􀆰 7  GUS staining of a two ̄week ̄old seedling transformed
with the ProRbohC ∶ GUS construct
of identity to one another in terms of their amino acid
sequences. The members of the three groups were
considered to be duplicated genes in each combina ̄
tionꎬ suggesting evolutionary conservation.
In some groupsꎬ the members had similar tran ̄
scriptional profiles (AtRbohAꎬ AtRbohB and AtRbo ̄
hGꎻ AtRbohH and AtRbohJ). The members of each
group might have overlapping functions in those or ̄
gans in which they are expressed together. We ob ̄
tained T ̄DNA insertion lines of all Rboh genesꎬ and
then we investigated the morphology of the aerial
parts of these insertion lines. Except of AtrbohCꎬ
9644期      SUN Xu ̄dong et al.: Molecular and Functional Comparisons of Reactive Burst Oxygen Species Gene 􀆺     
there were no obviously differences between theses
insertion lines and wild ̄type plants. NtNOXꎬ a to ̄
bacco NADPH oxidaseꎬ functioned in pollen tube
growth (Potocky et al.ꎬ 2007). Transfection of to ̄
bacco pollen tube with NtNOX ̄specific antisense oli ̄
godeoxynucleotides resulted in decreased amount of
NtNOX mRNAꎬ lower NOX activity and pollen tube
growth inhibition. The ROS scavengers and the NOX
inhibitor diphenyleneiodonium chloride (DPI) also
inhibited growth and ROS formation in tobacco pol ̄
len cultures. Exogenous hydrogen peroxide rescued
the growth inhibition caused by NOX antisense oli ̄
godeoxynucleotides (Potocky et al.ꎬ 2007). AtRbo ̄
hH and AtRbohJꎬ are NtNOX homologsꎬ are spe ̄
cially expressed in floral buds. The AtrbohH and Atr ̄
bohJ single mutantsꎬ pollen tube tip growth was no
obviously defect compared to the wild typeꎻ howeverꎬ
tip growth was severely impaired in the double mu ̄
tant. In vivo imaging showed that ROS accumulation
in the pollen tube was impaired in the double mu ̄
tant. ROS production by AtRbohH and AtRbohJ is
essential for proper pollen tube tip growthꎬ and fur ̄
thermoreꎬ that Ca2+  ̄induced ROS positive feedback
regulation is conserved in the polarized cell growth to
shape the long tubular cell ( Kaya et al.ꎬ 2014).
These results indicated that the members of Rboh
gene family might have redundancy function in plant
development.
RbohC / Root Hair Defective2 (RHD2) is one
of the Rboh family members required for root elonga ̄
tion. rhd2 / rbohC also displays impaird root hair e ̄
longationꎬ due to defective ROS production and Ca2+
uptakeꎬ this result indicates that RHD2 / AtRbohC is
function in cell expansion of roots (Foreman et al.ꎬ
2003). Similar phenomena were observed in epider ̄
mis cell of rosette leaf in rbohC mutants. The animal
NADPH oxidase gp91phox is regulated by Rac pro ̄
teinsꎬ and similar proteins in plants called Rops
(Rho ̄related GTPases from plants) have been shown
to be involved in correct cellular expansion in the
root elongation zoneꎬ the establishment of the tip ̄
high Ca2+ gradient and root ̄hair growth (Molendijk
et al.ꎬ 2001ꎻ Jones et al.ꎬ 2002ꎻ Wong et al.ꎬ 2007).
Examination of GUS staining in leaves revealed that
RbohC was expression in the developing leaves of
two ̄week ̄old seedlings. These results suggested that
AtRbohC maybe have similar function in the epider ̄
mal cell differentiation of developing leaves and root
hair elongation through establishment of the Ca2+ gra ̄
dient.
The Arabidopsis Rboh gene family has a diversi ̄
tied functions. AtRbohH and AtRbohJ display syner ̄
gistic funcion during pollen tube developmentꎬ
whereas AtRbohD and AtRbohF are involved in ROS
production in response to pathogens and ABA signa ̄
ling. The accentuated phenotypes of the double mu ̄
tants suggested that the different family members ex ̄
ist interaction in response to development and abiotic
or biotic stress. Further identification of loss ̄of ̄func ̄
tion lines for these genes should define additional
functions for plant development and response to
stress. ROS generated by plant Rboh also functions
in signaling pathway. Further characterization of the
cross ̄talk between ROS signaling pathway and other
signaling pathways may help to provide complex sig ̄
naling networks in response to developmental cues or
to environment.
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1744期      SUN Xu ̄dong et al.: Molecular and Functional Comparisons of Reactive Burst Oxygen Species Gene 􀆺