Altered Glucosinolate Profiles and Expression of Glucosinolate Biosynthesis Genes in Ringspot-Resistant and Susceptible Cabbage Lines

Abstract

Ringspot, caused by the fungus <i>Mycosphaerella brassicicola</i>, is a serious disease of <i>Brassica</i> crops worldwide. Despite noteworthy progress to reveal the role of glucosinolates in pathogen defense, the host⁻pathogen interaction between cabbage (<i>Brassica oleracea</i>) and <i>M. brassicicola</i> has not been fully explored. Here, we investigated the glucosinolate profiles and expression of glucosinolate biosynthesis genes in the ringspot-resistant (R) and susceptible (S) lines of cabbage after infection with <i>M. brassicicola</i>. The concomitant rise of aliphatic glucoiberverin (GIV) and indolic glucobrassicin (GBS) and methoxyglucobrassicin (MGBS) was linked with ringspot resistance in cabbage. Pearson's correlation and principle component analysis showed a significant positive association between GIV contents and the expression of the glucosinolate biosynthesis gene <i>ST5b-Bol026202</i> and between GBS contents and the expression of the glucosinolate biosynthesis gene <i>MYB34-Bol017062</i>. Our results confirmed that <i>M. brassicicola</i> infection induces the expression of glucosinolate biosynthesis genes in cabbage, which alters the content of individual glucosinolates. This link between the expression of glucosinolate biosynthesis genes and the accumulation of their respective glucosinolates with the resistance to ringspot extends our molecular sense of glucosinolate-negotiated defense against <i>M. brassicicola</i> in cabbage.