Glucosinolate Profile and Glucosinolate Biosynthesis and Breakdown Gene Expression Manifested by Black Rot Disease Infection in Cabbage

Abstract

Cabbage (<i>Brassica oleracea</i> var. <i>capitata</i>) is an economically important crop in the family Brassicaceae. Black rot disease is a top ranked cabbage disease, which is caused by <i>Xanthomonas campestris</i> pv. <i>campestris</i> (<i>Xcc</i>) and may reduce 50% crop loss. Therefore, we need a clear understanding of black rot disease resistance for sustainable disease management. The secondary metabolites, like Glucosinolate (GSL) presents in <i>Brassica</i> species, which plays a potential role in the defense mechanism against pathogens. However, there is little known about GSL-regulated resistance mechanisms and GSL biosynthesis and the breakdown related gene expression after black rot disease infection in cabbage. In this study, relative expression of 43 biosynthetic and breakdown related GSLs were estimated in the black rot resistant and susceptible cabbage lines after <i>Xcc</i> inoculation. Ten different types of GSL from both aliphatic and indolic groups were identified in the contrasting cabbage lines by HPLC analysis, which included six aliphatic and four indolic compounds. In the resistant line, nine genes (<i>MYB122-Bol026204</i>, <i>MYB34-Bol017062</i>, <i>AOP2-Bo9g006240</i>, <i>ST5c-Bol030757</i>, <i>CYP81F1-Bol017376</i>, <i>CYP81F2-Bol012237</i>, <i>CYP81F4-Bol032712</i>, <i>CYP81F4-Bol032714</i> and <i>PEN2-Bol030092</i>) showed consistent expression patterns. Pearson's correlation coefficient showed positive and significant association between aliphatic GSL compounds and expression values of <i>ST5c-Bol030757</i> and <i>AOP2-Bo9g006240</i> genes as well as between indolic GSL compounds and the expression of <i>MYB34-Bol017062</i>, <i>MYB122-Bol026204</i>, <i>CYP81F2-Bol012237</i>, <i>CYP81F4-Bol032712</i> and <i>CYP81F4-Bol032714</i> genes. This study helps in understanding the role of GSL biosynthesis and breakdown related genes for resistance against black rot pathogen in cabbage, which could be further confirmed through functional characterization either by overexpression or knock-out mutation.