The Role Of Transcription Factor SlMYC2 In MeJA-induced Tomato Fruit Quality And Disease Resistance And The Construction Of Its Overexpression Vector

Fruits and vegetables are susceptible to quality deterioration by own metabolism and pathogens infections,which affects the edible value and causes considerable postharvest losses.Methyl jasmonate(Me JA),an endogenous regulator,involves in the quality maintenance and defense responses of many plants.MYC2,an important transcription factor in jasmonic acid(JA)signaling pathway,plays key roles in Me JA-induced secondary metabolism,defense responses and regulation of growth and development of plants.However,the functions of MYC2 in Me JA-induced fruit quality and defense response are far from being clearly understood.In present work,tomato fruit,a model material,were treated with Me JA to study the functions of Me JA in postharvest fruit quality regulation and defense responses.Moreover,the Sl MYC2-silenced fruit were used to study the roles of Sl MYC2 in Me JA-induced tomato fruit disease resistance.In addition,we also established Sl MYC2 overexpression vector to further verified the roles of Sl MYC2 in regulation of fruit quality.The main results were as follows:(1)Compared with control and ethephon treatment,application of Me JA not only induced the activities of superoxide dismutase,peroxidase,catalase,and ascorbate peroxidase and the accumulation of antioxidant compounds(total phenolics,flavonoids,ascorbic acid and reduced glutathione),but also inhibited the decrease of firmness and the increase of electrical conductivity,superoxide anion and the hydrogen peroxide,which were related with antioxidant capacity and postharvest fruit quality;(2)The treatment with Me JA enhanced the activitise of disease-related enzymes including phenylalanine ammonia-lyase,polyphenol oxidase,?-1,3-glucanase and chitinase,inhibited the decrease of ?-tomatine content,induced the relative expression levels of Sl MYC2,Sl PR1,Sl PR2 a,Sl PR2 b and Sl PR3 b,and enhanced the disease resistance of tomato fruits;(3)The silence of SlMYC2 significantly inhibited the inductive effects of Me JA on disease-related enzymes,antioxidant enzyme activities,ascorbic acid,lycopene content,total phenolic content and other resistant substances in tomato fruit,so the disease development was aggravated in Sl MYC2-silenced + Me JA treatment fruit,suggesting that Sl MYC2 might play a positive role in Me JA-induced tomato fruit disease resistance;(4)The overexpression vector of pCAMBIA1300-Sl MYC2 was successfully constructed,and Sl MYC2 was also overexpressed in tomato fruit by infection p CAMBIA1300-Sl MYC2 with Agrobacterium.The overexpression of Sl MYC2 in fruit delayed the deterioration of postharvest quality and induced fruit disease resistance,further indicating that Sl MYC2 played positive regulatory roles in fruit defense responses.