Blackgram, an important legume crop, faces the constraint of Mungbean yellow mosaic India virus (MYMIV)-stress resulting in severe crop penalty. MYMIV-resistant plants exhibit incompatible response via a cognate CYR1 gene-mediated interaction with virus effector molecule. In this study, we searched for the susceptible allele of the “R” gene in Cv. T9. Southern hybridization study confirmed presence of an allele in Cv. T9. However, transcripts of the CYR1 could not be detected either by RT-PCR or by Northern hybridization in Cv. T9 and also in other susceptible blackgram line. The allele was isolated, sequenced and referred as cyr1. In silico study revealed that cyr1 also encodes a CC-NBS-LRR protein like CYR1. However the CC domain of cyr1 is truncated by 128 amino acid residues indicating functional impairment with respect to the signal transduction after pathogen invasion. Comparative 3D structural modeling, hydrogen bonding and Van der Waals interaction studies revealed differences between CYR1 and cyr1. Lys519 and Thr490 present in the largest pockets of the CYR1 are the key interacting hotspots between CYR1 and MYMIV coat protein (CP). The weak Van der Waals interactions and intermolecular hydrogen bonding between cyr1 and CP confers less stability to the molecular recognition complex, unlike CYR1. Thus, the present investigation revealed Cv. T9 shows compatible interaction with MYMIV due to the truncation in the cyr1 sequence and consequent structural difference in the N-terminal of CC-domain.
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