ROS Dependent Antifungal and Anticancer Modulations of Piper colubrinum Osmotin.

Osmotin, a plant defense protein, has functional similarity to adiponectin, an insulin sensitizingsensitising hormone secreted by adipocytes. We speculated that Piper colubrinum Osmotin (PcOSM) could have functional roles in obesity-related cancers, especially breast cancer. Immunofluorescence assays, flow cytometry, cell cycle analysis and a senescence assay were employed to delineate the activity in MDAMB231 breast cancer cell line. PcOSM pre-treated P. nigrum leaves showed significant reduction in disease symptoms correlated with high ROS production. In silico analysis predicted that PcOSM has higher binding efficiency with adiponectin receptor compared to adiponectin. PcOSM was effectively taken up by MDAMB231 cancer cells which resulted in marked increase in intracellular ROS levels leading to senescence and cell cycle arrest in G2/M stage. This study provides evidence on the ROS mediated direct inhibitory activity of the plant derived osmotin protein on the phytopathogen Phytophthora capsici, and the additional functional roles of this plant defense protein on cancer cells through inducing ROS associated senescence. The strong leads produced from this study could be pursued further to obtain more insights into the therapeutic potential of osmotin in human cancers.

Resistance Genes in Piper colubrinum: In Silico Survey From Leaf Transcriptome and Expression Studies Upon Challenge Inoculation with Phytophthora capsici.

The oomycetes, Phytophthora capsici, cause foot rot disease in black pepper. Piper colubrinum Link, a distant relative of cultivated black pepper, is highly resistant to this destructive pathogen. Identification of resistance (R) genes in P. colubrinum and the study of its expression profile during interaction with the pathogen can help in understanding the resistance mechanism involved. In the present study, 1289 R gene-related transcripts were mined from P. colubrinum transcriptome, clustered, and classified according to the conserved motifs and domains. Transcripts belonging to four major R gene classes were identified in P. colubrinum, but TIR-NBS-LRR-type R genes were absent. The relative expression of 12 selected R genes was studied using two virulent isolates of P. capsici, and these were found to be upregulated in the initial hours of plant pathogen interaction. The R genes studied were expressed even in aseptically maintained tissue-cultured plants and uninoculated greenhouse-grown plants at basal level suggesting that the plants are geared up with the R gene all the time and are under continuous surveillance for the pathogen and basal level of R gene expression do not require a pathogen trigger. ACT, ATUB, and EIF3E were identified as the most stable reference genes that can be used for real-time PCR study. The present study identified promising R genes in P. colubrinum which can be used in developing Phytophthora-resistant black pepper.

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.