BMC Genomics 2009, 10:415 http://www.biomedcentral.com/1471-2164/10/415 calcium signaling such as calmodulin, calcium dependent calmodulin independent kinase, CIP kinase and calcium/ calmodulin-regulated receptor-like kinase in both the genotypes indicating an elaborate role of calcium signal- ing in immune response. The subsets of 14-3-3 proteins were also identified in both susceptible and resistant gen- otypes. For example, contigs 527, 568, 947 and singletons CaF1_WIE_13_A_05, CaF1_WIE_55_G_01 representing 14-3-3 gene family were present in the resistant genotype while the other member of this gene family, contig 133, was present only in the susceptible one. 14-3-3 has earlier been shown to interact with fusicoccin, the fungal toxin that causes membrane hyperpolarization through activa- tion of plasma membrane H+ATPase [25]. Other pathos- tress-responsive signaling components identified are WD40-like protein, response regulator receiver, and leu- cine-rich repeat (LRR) proteins. While WD40 and LRR proteins were found in both the genotypes, response reg- ulator receiver was exclusive to the susceptible genotype. The LRR proteins are known to play role in defense sign- aling [26]. While WD40-like proteins are reported to be involved in varied functions including organogenesis [27]; vacuolar trafficking [28] and light signaling [29], their role in immune response is not known. The potentially increased activity of various signaling pathways is associated with differential expression of many families of transcription factors during plant patho- genesis [30-32]. The functional class of transcription asso- ciated genes, in this study, constituted about 3.58% of the total ESTs that comprised families of transcription factors including zinc finger, MYB, BEL1-like homeodomain transcription factor, homeodomain leucine zipper HDZ3, G-box binding PG2, Zinc finger GATA-type, putative AP2- binding protein, bHLH and WRKY. While exploring the source of the ESTs coding for these transcription factors, an important and noteworthy observation was that a par- ticular class of transcription regulators showed predomi- nance or was specific to either susceptible or resistant genotype. For example, Myb and HDZ classes were pre- dominant, whereas, PR related transcription factor and WRKY were exclusive to the resistant genotype. On the other hand BEL1-like homeodomain transcription factor, NOT2/NOT3/NOT5 and G-box binding protein PG2 were found only in the susceptible genotype. This data suggests that interplay of a broad spectrum of transcription factors possibly regulates multiple signaling cascades during immune-stress. Various RNA binding proteins have potential to modulate gene expression and might be involved in processes like RNA metabolism, mRNA splicing, ribosome biogenesis, transport and translation. We observed the presence of dead box RNA helicase, pre-mRNA processing ribonucle- oprotein binding region, splicing factor 3B subunit 10 and RNA-binding region RNP-1 during vascular wilt of chickpea. All these genes were more abundant in resistant genotype. While dead box RNA helicase was reported to be involved in development and stress responses [33], the role of splicing factor and RNA-binding region RNP-1 in pathostress is yet to be established. Genes involved in translation, post translational modifications and protein turnover Cellular processes like translation, post translational event and protein turnover are crucial for cell survival under different developmental stages and varied environ- mental conditions. In the present study, this class consti- tuted about 8.84% of ESTs and comprised predominantly the ribosomal proteins apart from some translation initi- ation factors. Genes encoding major ribosomal proteins such as S6, S8, S9, and L24/L26 were found both in sus- ceptible and resistant genotypes. Translation factor SUI1 homolog and eukaryotic elongation factors (EF-1 and EF-2) play a pivotal role in protein biosynthesis. Their presence in CaUnigene set is indicative of their role in immune response. A particularly sensitive, rapid and reversible response to environmental stimuli or to a programmatic change in cell state is the post-translational modification of specific proteins. In our study, 4.27% of the CaUnigenes corre- spond to proteins involved in protein modifications and turnover. The presence of cysteine proteinases and cyclo- philin-type peptidyl-prolyl cis-trans isomerases more pre- dominantly in resistant genotype indicate their role in pathostress responses. The presence of heat shock protein, DnaJ is interesting as it has been shown to be involved in different environmental stresses including high tempera- ture and salinity treatment [34]. Our results revealed the presence of a wide range of proteins involved in protein turnover that include ubiquitin conjugating enzyme E2, ubiquitin-protein ligase, 20S proteasome alpha 6 subunit, F-box protein and protein disulphide in both the geno- types. In plants, ubiquitin/proteasome pathway of protein degradation has been implicated in defense [35]. These results suggest that regulated protein synthesis, modifica- tion and protein turnover may play central role in ena- bling plants to alter their proteome to maximize their chances of survival under adverse conditions. Genes encoding nucleotide binding proteins In our study, GTP binding proteins were found to be the major class of nucleotide binding proteins in susceptible as well as resistant genotypes. The stress-responsive pre- dominant GTP binding proteins were of Ras, Rab and Ran type. ESTs encoding ras-like small monomeric GTP-bind- ing protein and GMPase were present in the susceptible genotype while Rab, RAB7C, GTP cyclohydrolase and RabGAP/TBC were found only in the resistant one. How- Page 5 of 21 (page number not for citation purposes)