Studies On The Role Of Glucocinates In Resistance Of Arabidopsis Against Sclerotinia Sclerotiorum

Glucosinolates are a group of nitrogen- and sulfur- containing plant secondary metabolites, and its degradation products can reduce herbivore feeding or attract natural enemies of those herbivores, which effectively protect the plant-from herbivorous insects infringement and defense or reduce the damage after pathogen infection or even directly kill pathogens. It is therefore considered that glucosinolates play an important role on regulating plant resistance to biotical stress, such as pathogen.Sclerotinia sclerotiorum is a necrotrophic plant pathogen with a broad range of host. It can cause Sclerotiniose, a world wide plant disease, and is one of the most harmful and widely distributed diseases in the production of agricultural crops, including oil crops and vegetables. Infection of plants by Sclerotinia sclerotiorum can induce programmed cell death and defensive gene expression. In the present study, a variety of glucosinolate mutants and the corresponding wild types of Arabidopsis thaliana were used to study the symptom, active oxygen species, the relative water content, relative conductivity and the changes in resistance gene expression of Arabidopsis thaliana plants under the infection of Sclerotinia sclerotiorum, in order to clarify the role and mechanism of glucosinolates in resistance of Arabidopsis thalidna to Sclerotinia sclerotiorum, Our research will provide a theoretical basis for enhancing the resistance of crop to Sclerotinia sclerotiorum by modification of glucosinolate composition and content in crops through chemical regulation and metabolic engineering.1. An infection system of Sclerotinia sclerotiorum to Arabidopsis thaliana was established and it was found that Sclerotinia sclerotiorum could infect the ecotype Col-0. The symptoms of the plants began from the location of mycelial block vaccinated, gradually, a brown hygrophanous disease spot was formed, and then the lesions expanded, the inoculated leaves were completely rotten. The whole plant was yellowing, wilted, and stop of growth. Hyphae spread from the inoculation site to the whole plant, leading to the totten and even death of the whole plant. 2. Four indole glucosinolate mutants of Arabidopsis thaliana ecotype Columbia (myb5l, cyp792, cyp79b2cyp79b3, cyp81f2) and the wild type Col-0, treated with Sclerotinia sclerotiorum were used to study the role of indole glucosinolates in resistance of Arabidopsis thaliana to Sclerotinia sclerotiorum.. The results showed that the plant of double mutant cyp79b2cyp79b3 with complete loss of indole glucosinolates was weakest in resistance to Sclerotinia sclerotiorum, followed by the mutants of cyp79b2 and myb51 which has a significant decline both in individual and total indole glucosinolate content, cyp81f2 mutant with completely missing of the 4-Methoxy-indole-3-methyl glucosinolates, and finally the wild-type Arabidopsis thaliana Col-0. The double mutant cyp79b2cyp79b3 resulted in the highest incidence rate, the fastest process, the largest increase in reactive oxygen species, the highest decline in relative water content and relative electrical conductivity, and the lowest expression of resistance genes (PDF 1.2 and PR 1). The finding of weaker resistance of four indole glucosinolates mutants to Sclerotinia sclerotiorum than the wild type suggested that indole glucosinolates play a positive and important role in resistance of Arabidopsis thaliana to Sclerotinia sclerotiorum.3. Three aliphatic glucosinolate mutants (myb28, myb29, myb28myb29) and the wild type Col-0, treated with Sclerotinia sclerotiorum were used to study the role of aliphatic glucosinolates in resistance of Arabidopsis thaliana to Sclerotinia sclerotiorum. The results showed that the plant of double mutant myb28myb29 with complete loss of aliphatic glucosinolates was weakest in resistance to Sclderotinia sclerotiorum, followed by the mutants of myb28 with complete absence of long-chain aliphatic glucosinolates and loss of short-chain aliphatic glucosinolates by 50%, myb29 mutants with loss of short-chain aliphatic glucosinolates by 50%, and finally the wild-type Arabidopsis thaliana Col-0. The double mutant myb28myb29 resulted in the highest incidence rate, the fastest process, the largest increase in reactive oxygen species, the highest decline in relative water content and relative electrical conductivity, and the lowest expression of resistance genes (PDF 1.2 and PR 1). Our results indicated that aliphatic glucosinolates also play a role in the resistance of Arabidopsis thaliana to Sclerotinia sclerotiorum. Our data suggested that both indole and aliphatic glucosinolates in Arabidopsis thaliana play a role in the resistance to Sclerotinia sclerotiorum. However, compared with aliphatic glucosinolate mutants, the indole glucosinolate mutants showed weaker resistance to Sclerotinia sclerotiorum, which indicated that glucosinolates in particular, indole glucosinolates in Arabidopsis thaliana might play an important role in resistance to Sclerotinia sclerotiorum.