Calcium-triggered accumulation of defense-related transcripts enhances wheat resistance to leaf blast

Abstract

Calcium (Ca) is an essential macronutrient for plant growth, but its role in plant disease resistance remains largely elusive. Here, we investigated whether Ca increases the abundance of defense-related transcripts and enhances wheat resistance to leaf blast, caused by Pyricularia oryzae. To address these issues, wheat plants were grown in nutrient solution containing three Ca concentrations (0.26, 2.6 and 5 mM) either non-inoculated or inoculated with P. oryzae. Ca content in the leaves increased from 1.3 to 4.1% and blast severity decreased from 36.8 to 8.2% as the Ca concentration in the nutrient solution increased from 0.26 to 5 mM. The expression level of salicylic (SA) and jasmonic acid (JA) pathways gene markers (pathogenesis-related 1 and allene oxide synthase, respectively) as well as chitinase, β-1,3-glucanase, phenylalanine ammonia lyase, peroxidase and polyphenol oxidase was higher in inoculated plants grown with 5 mM Ca than in those grown with 0.26 mM Ca. Collectively, results suggest that Ca, in addition to its well-known effect in cell wall strengthening and inhibition of fungal-secreted pectolytic enzymes, plays an active role in wheat resistance to leaf blast through upregulation of defense-related gene expression upon P. oryzae infection. Both of SA and JA pathways seems to make up a central node in such Ca-mediated resistance.