全 文 ：Micro-colinearity and Conservation of High
Gene Density in Small and Large Grass Genomes
Beat Keller
(Inst itute o f Plan t B iology , U niversity o f Zǜrich Zoll ikerst rasse 107 , CH-8008 Zǜr ich , Swi tz erla nd)
　　Comparative genomic analysis at the genetic map level has
show n ex tensive conserv ation of the gene order between the dif-
ferent g rass genomes in many chromosomal regions.However ,
little is known about the gene organization in grass genomes at
the microlevel.Comparison of g ene coding reg ions between
maize, rice and sorghum showed that the distance betw een the
genes is correlated w ith the genome size.We have investig ated
the microcolinearity at Lrk gene loci in the genomes of four
g rass species:whea t , barley , maize and rice.The Lrk genes ,
w hich encode receptor-like kinases , w ere found to be consistent-
ly associated w ith another type of recepto r-like kinase(Tak)on
chromosome groups 1 and 3 in T riticeae and on chromosomes
homoeologous to T riticeae g roup 3 in the genomes in rice and
maize.On Triticeae chromosome group 1 , Tak and Lrk toge th-
er with genes putatively encoding NBS/ LRR proteins form a
cluster of g enes possibly involved in signal transduction.Com-
parison of the gene composition at or thologous Lrk loci in
wheat , barley and rice revealed a maximal gene density of one
gene per 4～ 5 kb , very similar to the gene density in Arabidop-
sis thaliana.We conclude that small and larg e g rass genomes
contain regions w hich are highly enriched in genes w ith very lit-
tle or no repetitive DNA.The comparison of the gene organiza-
tio n suggested various genome rearrangements during the evolu-
tio n of the different grass species , including a duplica tion of the
Lrk region specific for the T riticeae on group 1 chromosomes.
We are now analy zing the gene organization in the Lrk regions
using BAC clones of the A genome(from T.monococcum)and
the D genome(from Ae.tauschii).In addition , we are investi-
gating the A , B and D genome in hexaploid w heat using a cos-
mid library.The accumulation of sequence information around
the Lrk loci in several species (o rtholog s) and in the same
species(paralogous genes)has allow ed comparisons of g enome
relationships in the investiga ted regions.
利用栽培一粒小麦的 BAC文库精细定位小麦基因
Beat Keller
(Inst itute o f Plan t B iology , U niversity o f Zǜrich Zoll ikerst rasse 107 , CH-8008 Zǜr ich , Swi tz erla nd)
关键词:一粒小麦;BAC 文库;小麦基因
中图分类号:Q75　　　文献标识码:A　　　文章编号:0253-9772(2001)-01-0043-02
High Resolution Mapping of Wheat Genes Using a
Triticum monococcum BAC Library
Beat Keller
(Inst itute o f Plan t B iology , U niversity o f Zǜrich Zoll ikerst rasse 107 , CH-8008 Zǜr ich , Swi tz erla nd)
　　The wheat genome is large(1.6×1010 bp)and complex
(hexaploid with the A , B and D-genomes).Map-based cloning
in such genomes requires at least one , but frequently several
w alking steps on a chromosome to reach the gene of interest ,
even if very closely linked markers are available for a “ chromo-
some landing” approach.Chromosome w alking in w heat has of-
ten been considered to be very difficult or impossible due to size
and complexity of the wheat genome and the high content of
repetitive sequences.We are interested to clone two genes on
chromosome 1AS by map information only:the Lr10 leaf rust
431 期　　　　　　　　　　　　　李振声等:小麦分子与细胞遗传学研讨会论文摘要　　　　　　　　　　　　　　　
DOI :10.16288/j.yczz.2001.01.018
resistance gene and the Pm 3 powdery mildew resistance gene.
As no large inser t library of wheat w as available at that time , a
collaborative effor t of several research groups was started to cre-
ate a BAC libr ary of T.monococcum , a cultivated diploid with a
close relativ e of the A genome in hexaploid wheat.The BAC li-
brary contains mo re than six genome equivalents and is double
spotted on filters which are available from our lab.A mapping
population of 3150 F2 plants segregating for the Lr10 gene has
been established and a marker closely linked to the gene(0.1
cM)was found.This marker w as the star ting point for the as-
sembly of a phy sical contig in T.monococcum .The use of sub-
cloned BAC ends for mapping was only successful in a few cases
but in general w as problematic.To derive probes from BAC
clones fo r genetic mapping w e developed a rapid “ low pass” se-
quencing protocol.Shotgun DNA libraries from BAC clones
were generated and sequenced at 1.5×genome equiv alents.The
obtained sequence data w ere sufficient to identify coding regions
(usually g ood probes fo r mapping)as well as non-coding , non-
repetitive sequences which sometimes can also be mapped and
used as probes for fur ther walking steps.P robes derived from
sequencing have also to be physically mapped on the BAC clones
to identify sequences close to the ends o f the BACs.Four walk-
ing steps have been completed until now using these approaches.
This resulted in a phy sical contig spanning around 440 kb on
chromosome 1AS.Prog ress will also be repor ted on the mapping
o f the Pm3b gene.
图位克隆小麦抗叶锈基因 Lr1
凌宏清 ,Beat Keller
(Inst i tute of P lant Biology , Universi ty of Zur ich , Zollikerst rasse 107.CH-8008 Zurich , Swi tzerland)
关键词:图位克隆;抗叶锈;小麦
中图分类号:Q343.1　　　文献标识码:A　　　文章编号:0253-9772(2001)-01-0044-01
Towards map-based cloning of the leaf rust
disease resistance gene Lr1 in wheat
LING Hong-qing ,Beat Keller
(Inst i tute of P lant Biology , Universi ty of Zur ich , Zollikerst rasse 107.CH-8008 Zurich , Swi tzerland)
　　Leaf rust , caused by Puccinia recondita Rocb.ex Desm.
f.sp.tritici Eriks.&Henn , is one of the most important dis-
eases in wheat w orldwide.There are more than 40 resistance
genes against wheat leaf rust and used in wheat breeding.The
Lr1 resistance gene is one of them , originates from hexaploid
w heat and is present in a number of cultivars.It is a dominant
g ene located at the distal end of chromosome 5DL of wheat.We
are w orking on isolation of the Lr1 gene using a map-based gene
cloning approach.Generation o f a saturated map around the tar-
get gene is the first step of map-based gene cloning.Two segre-
ga ting F 2 populations Thatcher Lr1 ×Thatcher(2814 individual
plants)and Thatcher Lr1 ×Frisal(832 plants)are used fo r fine
mapping of the Lr1 gene.Three micro-satellite markers
(GWM654 , GWM269 and GWM272)and four RFLP markers
(BCD1421 , Psr567 , pTAG621 and ABC718)are used to ana-
ly ze the two mapping populations.The micro-satellite marker
GWM272 and the RFLP marker ABC718 are tightly linked to
Lr1 gene.The two markers are located at 0.1 cM from the
Lr1 gene.Fo r physical mapping of the Lr1 gene , genomic
BAC and YAC libraries of barley and T.tauschii (D-genome)
have been screened with the RFLP marker ABC718.Five BAC
clones from a genomic library of T.tauschii , six from a genomic
library of barley and one YAC clone from a YAC library of bar-
ley were isolated.All ends of BAC and YAC clones have been
isolated and analy zed.The ends o f BAC and YAC clones from
barley could not be used for mapping because they are repetitive
o r did not hybridize with wheat DNA.Most of BAC ends from
T.tauschii BAC clones showed repetitive sequences.Tw o BAC
ends isolated from BAC clone L-1 121K23 (100 kb) are poly-
morphic and w ere mapped at the same position as the RFLP
marker ABC718.We did not find any recombinants in the 100
kb reg ion around the RFLP marker ABC718.
44 　　　　　　　　　　　　　　　　　遗　传 HEREDITAS(Beijing)　2001　　　　　　　　　　　　　　　23卷