Plant virus interaction mechanism and associated pathways in mosaic disease of small cardamom (Elettaria cardamomum Maton) by RNA-Seq approach.

Small cardamom (Elettaria cardamomum), grown in limited coastal tropical countries is one of the costliest and widely exported agri-produce having global turnover of >10 billion USD. Mosaic/marble disease is one of the major impediments that requires understanding of disease at molecular level. Neither whole genome sequence nor any genomic resources are available, thus RNA seq approach can be a rapid and economical alternative. De novo transcriptome assembly was done with Illumina Hiseq data. A total of 5317 DEGs, 2267 TFs, 114 pathways and 175,952 genic region putative markers were obtained. Gene regulatory network analysis deciphered molecular events involved in marble disease. This is the first transcriptomic report revealing disease mechanism mediated by perturbation in auxin homeostasis and ethylene signalling leading to senescence. The web-genomic resource (SCMVTDb) catalogues putative molecular markers, candidate genes and transcript information. SCMVTDb can be used in germplasm improvement against mosaic disease in endeavour of small cardamom productivity. Availability of genomic resource, SCMVTDb: http://webtom.cabgrid.res.in/scmvtdb/.

Interplay of genes in plant-pathogen interactions: In planta expression and docking studies of a beta 1,3 glucanase gene from Piper colubrinum and a glucanase inhibitor gene from Phytophthora capsici.

Oomycete pathogen, Phytophthora capsici is devastating for black pepper (Piper nigrum L.) and causes foot rot disease at all stages of plant growth. Phytophthora secretes a glucanase inhibitor protein (GIP), which is capable of inhibiting defence proteins like endoglucanases. In this particular study Quantitative PCR analysis, molecular docking studies and analysis of sequences of Glucanase inhibitor protein and beta-1,3 glucanse genes were done mainly depending on the data derived from Phytophthora capsici whole genome sequencing and Piper colubrinum RNA-sequencing (RNA-Seq). Amino acid sequence length of GIP gene from P. capsici was about 353 amino acids and that of glucanase pcEGase gene from P. colubrinum was about 312 amino acids. GIP gene from P. capsici showed high level of expression at early hours of the inoculation time period and pcEGase gene showed high level of expression at 16 hpi. High level of expression of pcEGase gene at 16 hpi is an indication that the GIP gene is successfully inhibited by the glucanase protein from the plant. Moreover insilico studies gave some hint on the importance of certain sites on the surfaces of both interacting proteins that might be having a role in binding of the two proteins and subsequent reactions thereof. Insilico analysis also conclusively proved that inhibition of glucanase inhibitor protein is mainly caused by recognition of an arginine as well as an isoleucine residue during the interaction of the two proteins.

Differential induction of chitinase in Piper colubrinum in response to inoculation with Phytophthora capsici, the cause of foot rot in black pepper.

Plant chitinases have been of particular interest since they are known to be induced upon pathogen invasion. Inoculation of Piper colubrinum leaves with the foot rot fungus, Phytophthora capsici leads to increase in chitinase activity. A marked increase in chitinase activity in the inoculated leaves was observed, with the maximum activity after 60 h of inoculation and gradually decreased thereafter. Older leaves showed more chitinase activity than young leaves. The level of chitinase in black pepper (Piper nigrum L.) upon inoculation was found to be substantially high when compared to P. colubrinum. RT-PCR using chitinase specific primers revealed differential accumulation of mRNA in P. colubrinum leaves inoculated with P. capsici. However, hyphal extension assays revealed no obvious differences in the ability of the protein extracts to inhibit growth of P. capsici in vitro.