Induction of peroxidase and polyphenol oxidase in Arachis hypogaea in response to treatment with Pseudomonas fluorescens and inoculation with Alternaria alternata

Abstract

The application of talc-formulation through seed, seed treatment plus foliar spray and foliar spray alone significantly reduced the leaf blight incidence both under greenhouse and field conditions. The groundnut plants treated with biocontrol agent and challenge inoculated with Alternaria alternata recorded significantly increased activity of Peroxidase isozyme (PO), Polyphenol oxidase isozymes (PPO) activity. Expression of PO2, PPO1 and PPO2 isoforms were found in all the plants treated with Pf1 while additional PO1, PPO3, PPO4 and PPO5 were observed in Pf1-treated plants followed by challenge inoculation with the pathogen.     

A semi-dominant NLR allele causes whole-seedling necrosis in wheat

Programmed cell death (PCD) and apoptosis have key functions in development and disease resistance in diverse organisms; however, the induction of necrosis remains poorly understood. Here, we identified a semi-dominant mutant allele that causes the necrotic death of the entire seedling (DES) of wheat (Triticum aestivum L.) in the absence of any pathogen or external stimulus. Positional cloning of the lethal allele mDES1 revealed that this premature death via necrosis was caused by a point mutation from Asp to Asn at amino acid 441 in a nucleotide-binding leucine-rich repeat protein containing nucleotide-binding domain and leucine-rich repeats. The overexpression of mDES1 triggered necrosis and PCD in transgenic plants. However, transgenic wheat harboring truncated wild-type DES1 proteins produced through gene editing that exhibited no significant developmental defects. The point mutation in mDES1 did not cause changes in this protein in the oligomeric state, but mDES1 failed to interact with replication protein A leading to abnormal mitotic cell division. DES1 is an ortholog of Sr35, which recognizes a Puccinia graminis f. sp. tritici stem rust disease effector in wheat, but mDES1 gained function as a direct inducer of plant death. These findings shed light on the intersection of necrosis, apoptosis, and autoimmunity in plants.

An R-gene in hexaploid wheat causes premature death of the entire seedling in the absence of any pathogen or external stimulus.