Non-host Resistance: DNA Damage Is Associated with SA Signaling for Induction of PR Genes and Contributes to the Growth Suppression of a Pea Pathogen on Pea Endocarp Tissue.

Lee A Hadwiger,Kiwamu Tanaka

doi:10.3389/fpls.2017.00446

Abstract

Salicylic acid (SA) has been reported to induce plant defense responses. The transcriptions of defense genes that are responsible for a given plant’s resistance to an array of plant pathogens are activated in a process called non-host resistance. Biotic signals capable of carrying out the activation of pathogenesis-related (PR) genes in pea tissue include fungal DNase and chitosan, two components released from Fusarium solani spores that are known to target host DNA. Recent reports indicate that SA also has a physical affinity for DNA. Here, we report that SA-induced reactive oxygen species release results in fragment alterations in pea nuclear DNA and cytologically detectable diameter and structural changes in the pea host nuclei. Additionally, we examine the subsequent SA-related increase of resistance to the true pea pathogen F. solani f.sp. pisi and the accumulation of the phytoalexin pisatin. This is the first report showing that SA-induced PR gene activation may be attributed to the host pea genomic DNA damage and that at certain concentrations, SA can be temporally associated with subsequent increases in the defense response of this legume.

Highlights

The salicylic acid (SA) signal receptor protein NPR1 has been reported in Arabidopsis (Wu et al, 2012), and NPR1 is a known link between SA signaling and defense gene activation
An alternate hypothesis for signal reception in the legume, pea, indicates that host cell chromatin can both serve as a receptor (Hadwiger, 2015a) and provide the site for increased transcription of pathogenesisrelated (PR) genes (Isaac et al, 2009)
The objective of the current research was to evaluate the aspects of legume defense simulation by SA that may correspond with the induction of non-host resistance by Fusarium solani f.sp. phaseoli (Fsph), an inducer of non-host resistance in pea tissue

Summary

Introduction

The salicylic acid (SA) signal receptor protein NPR1 has been reported in Arabidopsis (Wu et al, 2012), and NPR1 is a known link between SA signaling and defense gene activation. An alternate hypothesis for signal reception in the legume, pea, indicates that host cell chromatin can both serve as a receptor (Hadwiger, 2015a) and provide the site for increased transcription of pathogenesisrelated (PR) genes (Isaac et al, 2009). Recent reports (Neaualt et al, 1996; Yan et al, 2013) indicate that SA has an affinity for DNA, suggesting the potential of a DNA target site for SA that may add to or supersede reception by a cytoplasmic protein. The model pea endocarp/bean pathogen interaction system is a suitable system to research the role of SA in non-host defense in legumes

Objectives

Methods

Results