No abstract

Mungbean Yellow Mosaic India Virus (MYMIV) belonging to the genus begomovirus causes the yellow mosaic disease in a number of economically important edible grain legumes including mungbean (Vigna radiata), urdbean (Vigna mungo) and soybean (Glycine max). The disease is severe, critical, open spread and inflicts heavy yield losses annually. The objective of this study is to develop molecular markers linked to MYMIV-resistance to facilitate genotyping of urdbean and mungbean germplasms for MYMIV-reaction. Resistance-linked molecular markers were successfully developed from consensus motifs of other resistance (R) gene or R gene homologue sequences. Applying linked marker-assisted genotyping, plant breeders can carry out repeated genotyping throughout the growing season in absence of any disease incidence. Two MYMIV-resistance marker loci, YR4 and CYR1, were identified and of these two CYR1 is completely linked with MYMIV-resistant germplasms and co-segregating with MYMIV-resistant F₂, F₃ progenies of urdbean. The present study demonstrated that these two markers could be efficiently employed together in a multiplex-PCR-reaction for genotyping both V. mungo and V. radiata germplasms from field grown plants and also directly from the seed stock. This method of genotyping would save time and labour during the introgression of MYMIV-resistance through molecular breeding, as methods of phenotyping against begomoviruses are tedious, labour and time intensive.

We successfully produced two human ␤-defensins (hBD-1 and hBD-2) in bacteria as functional peptides and tested their antibacterial activities against Salmonella enterica serovar Typhi, Escherichia coli, and Staphylococcus aureus employing both spectroscopic and viable CFU count methods. Purified peptides showed approximately 50% inhibition of the bacterial population when used individually and up to 90% when used in combination. The 50% lethal doses (LD 50 ) of hBD-1 against S. Typhi, E. coli, and S. aureus were 0.36, 0.40, and 0.69 g/l, respectively, while those for hBD-2 against the same bacteria were 0.38, 0.36, and 0.66 g/l, respectively. Moreover, we observed that bacterium-derived antimicrobial peptides were also effective in increasing survival time and decreasing bacterial loads in the peritoneal fluid, liver, and spleen of a mouse intraperitoneally infected with S. Typhi. The 1:1 hBD-1/hBD-2 combination showed maximum effectiveness in challenging the Salmonella infection in vitro and in vivo. We also observed less tissue damage and sepsis formation in the livers of infected mice after treatment with hBD-1 and hBD-2 peptides individually or in combination. Based on these findings, we conclude that bacterium-derived recombinant ␤-defensins (hBD-1 and hBD-2) are promising antimicrobial peptide (AMP)-based substances for the development of new therapeutics against typhoid fever.

Yellow mosaic disease of Vigna mungo caused by Mungbean yellow mosaic India virus (MYMIV) is still a major threat in the crop production. A candidate disease resistance (R) gene, CYR1 that co-segregates with MYMIV-resistant populations of V. mungo has been isolated. CYR1 coded in silico translated protein sequence comprised of 1,176 amino acids with coiled coil structure at the N-terminus, central nucleotide binding site (NBS) and C-terminal leucine-rich repeats (LRR) that belongs to non-TIR-NBS-LRR subfamily of plant R genes. CYR1 transcript was unambiguously expressed during incompatible plant virus interactions. A putative promoter-like sequence present upstream of this candidate gene perhaps regulates its expression. Enhanced transcript level upon MYMIV infection suggests involvement of this candidate gene in conferring resistance against the virus. In silico constructed 3D models of NBS and LRR regions of this candidate protein and MYMIV-coat protein (CP) revealed that CYR1-LRR forms an active pocket and successively interacts with MYMIV-CP during docking, like that of receptor-ligand interaction; indicating a critical role of CYR1 as signalling molecule to protect V. mungo plants from MYMIV. This suggests involvement of CYR1 in recognizing MYMIV-effector molecule thus contributing to incompatible interaction. This study is the first stride to understand molecular mechanism of MYMIV resistance.