An Integrated Approach to Comprehend MYMIV-Susceptibility of Blackgram Cv. T9 Possessing Allele of <i>CYR1</i>, the Cognate R-Gene

Abstract

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.

Complex molecular mechanisms underlying MYMIV-resistance in Vigna mungo revealed by comparative transcriptome profiling

“…Hosts response to stresses relies on the timely recognition of the intruder there by integrating external cues into own cellular and physiological machinery. It was confirmed earlier that the MYMIV-susceptible T9 carried a defunct allele of the resistant gene resulted in a defective immune system 10 . Our previous study, which involved proteomic and EST analyses 5,12 showed significantly high expression of pathogen responsive genes in the resistant host that showed delayed-expression in the susceptible host.…”

“…Such interactions are governed by an array of genes activated over time and inducing signal transduction cascades that decide the fate of the host. However, presence of a defunct allele of the R-gene resulted in a compatible interaction influencing pathogen colonization 10 . Seven natural mutants derived from V .…”

Deciphering the role of alternative splicing as modulators of defense response in the MYMIV–Vigna mungo pathosystem

“…Considering the detrimental impact of MYMIV infection, characterization of the host's resistance is imperative to identify regulatory genes and to develop new cultivars with durable resistance. In V. mungo, resistance to MYMIV has previously been reported to be governed by a resistance (R) gene, CYR1 encoding NBS-LRR protein (Maiti et al, 2012); in contrast, a defunct version of the same R-gene resulted in susceptibility, which enables pathogen colonization (Patel et al, 2016). A suppression subtractive hybridization and next-generation sequencing (RNA-seq) approach identified the genes involved in MYMIV resistance to unravel the complex molecular interaction during compatible and incompatible interactions (Kundu et al, 2015;Kundu et al, 2019).…”

A source of resistance against yellow mosaic disease in soybeans correlates with a novel mutation in a resistance gene

“…To identify the ortholog of the black gram CYR-1 gene (Patel et al, 2016) in soybean, the complete sequence of the gene was retrieved from the Phytozome database (https://phytozomenext.jgi.doe.gov/), and BLASTP search engine was used to find the most similar sequences in the soybean genome. The most identical sequences of the predicted genes in soybeans were picked, which were further confirmed by wet lab experiments.…”

“…The CYR-1 gene was also found completely linked with MYMIV resistance in urdbean and mungbean (Maiti et al, 2011). In 2016, it was reported that the recessive form (cyr-1) of the CYR-1 gene is a susceptibility factor for YMD in black gram (Patel et al, 2016). In urdbean, RGA-1, CEDG180, ISSR811, and YMV-1 were found to be closely linked with MYMIV resistance (Basak et al, 2005;Souframanien and Gopalakrishna, 2006;Gupta et al, 2013).…”