Anatomy of a nonhost disease resistance response of pea to Fusarium solani: PR gene elicitation via DNase, chitosan and chromatin alterations

Abstract

Of the multiplicity of plant pathogens in nature, only a few are virulent on a given plant species. Conversely, plants develop a rapid “nonhost” resistance response to the majority of the pathogens. The anatomy of the nonhost resistance of pea endocarp tissue against a pathogen of bean, Fusarium solani f.sp. phaseoli (Fsph) and the susceptibility of pea to F. solani f sp. pisi (Fspi) has been described cytologically, biochemically and molecular-biologically. Cytological changes have been followed by electron microscope and stain differentiation under white and UV light. The induction of changes in transcription, protein synthesis, expression of pathogenesis-related (PR) genes, and increases in metabolic pathways culminating in low molecular weight, antifungal compounds are described biochemically. Molecular changes initiated by fungal signals to host organelles, primarily to chromatin within host nuclei, are identified according to source of the signal and the mechanisms utilized in activating defense genes. The functions of some PR genes are defined. A hypothesis based on this data is developed to explain both why fungal growth is suppressed in nonhost resistance and why growth can continue in a susceptible reaction.

Biostimulant activity of chitosan in horticulture

“…Radioactive labeled [ 3 H]-chitosan could be detected in both the cytoplasm and nuclei of the pea endocarp (Hadwiger et al, 1981). A mechanism of chitosan-induced PRP gene expression by a direct interaction with chromatin has been proposed (Hadwiger, 2013(Hadwiger, , 2015.…”

“…Alternatively, chitosan was proposed to activate defense gene expression via chromatin alterations (Hadwiger, 2015). Because chitosan has multiple positive charges, it shows a strong affinity to the negatively charged phosphate groups on DNA, which appears to be the cellular receptor.…”

Insights to plant–microbe interactions provide opportunities to improve resistance breeding against root diseases in grain legumes

“…Root exudates also comprise a large number of defence-related compounds with manifold effects on various rhizosphere-colonizing microbes, as reviewed by Baetz and Martinoia (2014). For instance, pisatin was the first phytoalexin identified and, since then, its interaction with fungal pathogens has served as a prime example to understand plant pathogenicity and nonhost resistance (Cruickshank & Perrin, 1960;Hadwiger, 2008Hadwiger, , 2015. Pisatin is produced by peas and acts as an important defence molecule against fungal pathogens (Preisig et al, 1990).…”

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

“…Maximal transcription of PR genes may depend on a “perfect storm” of conditions and the fragility of chromosomal regions adjacent to the promoter and open reading frame of the gene. Regions of dispersed pea chromatin that are also regions of intense transcription have been detected by electron microscopy (Hadwiger, 2015a) as resistance is developing. Genes within eukaryotic tissues can possess the requisite transcription complex with the proper transcription factors in place and still be silent or stalled (Li et al, 2007).…”

“…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 pathogenesis-related (PR) genes (Isaac et al, 2009). DNA damage within chromatin can also initiate signaling cascades in animal tissues (De Dieuleveult et al, 2016) and is dependent on ubiquitin (Stewart et al, 2009).…”