Submitted to: Plant Cell Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2011
Publication Date: 6/1/2011
Citation: Madrid, E., Rajesh, P., Millan, T., Chen, W. 2011. Characterization and genetic analysis of an EIN4-like sequence (CaETR-1) located in QTL ARI implicated in Ascochyta blight resistance in chickpea. Plant Cell Reports. 31:1033-1042. DOI 10.1007/s00299-011-1221-9. Interpretive Summary: Ascochyta blight is a devastating disease of chickpea. Despite extensive studies on the pathogen and the host, very little is known about the mechanisms of chickpea resistance to the disease. This study isolated and sequenced a gene in the chickpea genomic region responsible for resistance to ascochyta blight. The full-length DNA sequence of this gene in the resistant cultivar FLIP82-94C is 4,428 bp including the nontranscribed 3’-end. However, the sequence in the susceptible chickpea genotype PI359075 is shorter, and has 730 bp missing in the 3’ end. The missing region makes the gene nonfunctional in the susceptible chickpea. This gene is determined to be an ethylene receptor reported and is named CaETR-1. This is the first ethylene receptor gene, and the first gene with known function related to blight resistance, to be isolated and sequenced from chickpea. Isolation and sequence-characterization of the CaETR-1 gene not only afford means for developing molecular markers for resistance, but also will facilitate investigation into resistance mechanisms of chickpea to Ascochyta blight.
Technical Abstract: Two different alleles of an ethylene receptor gene (CaETR-1) of chickpea (Cicer aritinum) were isolated and characterized through synteny analysis with genome sequences of Medicago truncatula. The full length of CaETR-1 in cultivar FLIP84-92C (CaETR-1a) is 4,428 bp including the polyadenylation signal in the 3’ untranslated region (UTR), whereas the allele in PI359075 (CaETR-1b) had a 730 bp deletion in the UTR. The deduced protein, which is 760 amino acids long, is the same in both alleles. CaETR-1 belongs to the group II of the ethylene receptors and contains all the domains that define EIN4 homologues in Arabidopsis: three transmembrane domains, a putative ethylene-binding region at the amino terminus, a GAF domain associated with cGMP binding, a Histidine kinase domain, and a response regulator region. This is the first ethylene receptor gene, and the first gene with known function located in the genomic region where Ascochyta blight QTL-1AR has been mapped isolated and sequenced from chickpea. Further characterization of this gene will facilitate understanding of biotic and abiotic resistance mechanisms in chickpea and the development of direct markers for marker-assisted selection in chickpea breeding.