Wheat EST resources for functional genomics of abiotic stress.
BACKGROUND
Wheat is an excellent species to study freezing tolerance and other abiotic stresses. However, the sequence of the wheat genome has not been completely characterized due to its complexity and large size. To circumvent this obstacle and identify genes involved in cold acclimation and associated stresses, a large scale EST sequencing approach was undertaken by the Functional Genomics of Abiotic Stress (FGAS) project.


RESULTS
We generated 73,521 quality-filtered ESTs from eleven cDNA libraries constructed from wheat plants exposed to various abiotic stresses and at different developmental stages. In addition, 196,041 ESTs for which tracefiles were available from the National Science Foundation wheat EST sequencing program and DuPont were also quality-filtered and used in the analysis. Clustering of the combined ESTs with d2_cluster and TGICL yielded a few large clusters containing several thousand ESTs that were refractory to routine clustering techniques. To resolve this problem, the sequence proximity and "bridges" were identified by an e-value distance graph to manually break clusters into smaller groups. Assembly of the resolved ESTs generated a 75,488 unique sequence set (31,580 contigs and 43,908 singletons/singlets). Digital expression analyses indicated that the FGAS dataset is enriched in stress-regulated genes compared to the other public datasets. Over 43% of the unique sequence set was annotated and classified into functional categories according to Gene Ontology.


CONCLUSIONS
We have annotated 29,556 different sequences, an almost 5-fold increase in annotated sequences compared to the available wheat public databases. Digital expression analysis combined with gene annotation helped in the identification of several pathways associated with abiotic stress. The genomic resources and knowledge developed by this project will contribute to a better understanding of the different mechanisms that govern stress tolerance in wheat and other cereals.
Houde
Mario
M
Département des Sciences biologiques, Université du Québec à Montréal, Centre-ville, Montréal QC, H3C 3P8, Canada. houde.mario@uqam.ca
Belcaid
Mahdi
M
Ouellet
François
F
Danyluk
Jean
J
Monroy
Antonio F
AF
Dryanova
Ani
A
Gulick
Patrick
P
Bergeron
Anne
A
Laroche
André
A
Links
Matthew G
MG
MacCarthy
Luke
L
Crosby
William L
WL
Sarhan
Fathey
F
D000064:Acclimatization / Q000235:genetics*; D000596:Amino Acids / Q000378:metabolism; D021301:Antifreeze Proteins / Q000235:genetics; D001692:Biological Transport / Q000235:genetics; D016000:Cluster Analysis; D003080:Cold Temperature; D020451:Contig Mapping; D030541:Databases, Genetic / Q000600:supply & distribution*; D020224:Expressed Sequence Tags / Q000378:metabolism; D017343:Genes, Plant; D018745:Genome, Plant; D006295:Health Resources; D050356:Lipid Metabolism / Q000235:genetics; D008954:Models, Biological; D010788:Photosynthesis / Q000235:genetics; D010840:Phytosterols / Q000737:chemistry; D015398:Signal Transduction / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics; D014908:Triticum / Q000235:genetics*
D000596:Amino Acids; D021301:Antifreeze Proteins; D010840:Phytosterols; D014157:Transcription Factors