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

Abstract

Ringspot, caused by the fungus Mycosphaerella brassicicola, is a serious disease of Brassica crops worldwide. Despite noteworthy progress to reveal the role of glucosinolates in pathogen defense, the host–pathogen interaction between cabbage (Brassica oleracea) and M. brassicicola 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 M. brassicicola. 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 ST5b-Bol026202 and between GBS contents and the expression of the glucosinolate biosynthesis gene MYB34-Bol017062. Our results confirmed that M. brassicicola 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 M. brassicicola in cabbage.

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

“…Total GSL level was increased in leaves of B. rapa resistance cultivar upon infection of Leptosphaeria maculans and Fusarium oxysporum; whereas GSL was decreased in the susceptible line [43]. Recently, an increased level of GSL content was reported in resistance cabbage lines against ring spot disease [34]. A similar result was also found in the susceptible B. napus cultivars infected with Alternaria brassicae pathogen [43,44].…”

“…The GSL composition of the cabbage leaf samples was estimated as desulfo-GSL from three biological replicates for each of the control, mock-treated and Xcc infected plants using a modified Plants 2020, 9, 1121 4 of 16 HPLC method as previously described [33,34]. Frozen leaf tissue was treated with methanol and stored at −80 • C and then ground to a very fine powder.…”

“…In the case of plant pathogenic bacteria, myrosinase enzyme mediated GSL hydrolyzed products to act as tolerant against Xcc [11,17] Aliphatic GSL (sinigrin, gluconapin, glucoiberverin and glucoerucin) and indolic (glucobrassicin, hydroxyglucobrassicin, mythoxyglucobrassicin and neoglucobrassicin) content was found to increase due to Xcc infection in resistant cabbage line ( Figure 3) and represents its involvement in improving resistance against Xcc pathogen in cabbage. Aliphatic GSL (glucoiberverin, indolic; glucobrassicin and mythoxyglucobrassicin) was found to increase in cabbage lines resistant to Mycosphaerella brassicicola [34]. The aliphatic GSL compound, sinigrin showed a potential role in inhibiting the growth of S. sclerotiorum in kale and Arabidopsis [23,46].…”

Leptosphaeria maculans Alters Glucosinolate Accumulation and Expression of Aliphatic and Indolic Glucosinolate Biosynthesis Genes in Blackleg Disease-Resistant and -Susceptible Cabbage Lines at the Seedling Stage

“…This results supported the fact that glucosinolate mediated resistance in cabbage plants differs between seedling and adult stages. In recent studies, resistant cabbage plants inoculated with S. sclerotiorum and M. brassicicola showed increased accumulation of GIV (Abuyusuf et al, 2018a;Abuyusuf et al, 2018b) indicating its importance in resistance against diverse fungal infection.…”

“…By contrast, Li et al (1999a) in B. napus, reported a positive correlation between indolic glucosinolates induced upon the infection of Sclerotinia sclerotiorum and resistance of plants. In cabbage, inoculation of both resistant and susceptible plants with S. sclerotiorum and Mycosphaerella brassicicola revealed that both aliphatic and indolic glucosinolates raise in contents in the resistant lines (Abuyusuf et al, 2018a;Abuyusuf et al, 2018b). Furthermore, a recent study described possible mechanisms of overcoming glucosinolate-myrosinase-isothiocyanate defense system of Phoma lingam and Verticillium dahliae as these fungi species may degrade some primary glucosinolates to a less toxic level (Rahimi and Siamak, 2020).…”