| Corn stalk rot caused by Fusarium graminearum and ear rot(or kernel rot)caused by Aspergillus flavus are destructive diseases of maize(Zea mays L.),which can cause substantial loss of yield and quality.At present,there were very few reports about the cloning of resistance genes to stalk rot and kernel rot in maize,and the underlying mechanism is poorly understood.It has been well-known that phytohormones play important roles in regulating plant responses to a wide variety of internal and external stimuli,among which jasmonic acid(JA)and its derivatives,collectively referred to as jasmonates(JAs),have been extensively studied for their function in plant development and immunity to pests and pathogens.However,the function of JA pathway in the regulation of stalk rot resistance in maize has not been well studied.To better understand and explore the function of JA pathway in regulating the stalk rot resistance in maize,a bioinformatics analysis of maize JAZ gene family was performed.There are 23 ZmJAZ genes in maize genome,which are distributed over eight chromosomes.Multiple alignment and motif analysis indicated that all ZmJAZ proteins share two conserved domains,TIFY domain and Jas domain.Phylogenetic analysis revealed that the ZmJAZ family could be divided into 10 subgroups.The expression data from different tissues and from qTeller showed that the ZmJAZ genes displayed differential tissue-specific expression patterns at various maize developmental stages.Like in modern plant species,ZmJAZs aslo interact with ZmCOI1,and the interaction is dependent on Coronatine(COR),as confirmed by Y2H approach.To identify the potential interacting components of ZmJAZs,a Y2H library was constructed using maize seedlings infected with F.graminearum.ZmJAZ17 was used as a "Bait",to screen the library,and WD40-r was identified as a ZmJAZ17-interacting protein.Moreover,JA-biosynthetic mutant,opr8-2,was more resistant to Fusarium graminearum.All together,it suggested that JA pathway plays essential role in modulating the resistance to stalk rot caused by F.graminearum.Ethylene(ET)emitted by plant tissues has been broadly reported to play important roles in plant development,response to environmental stresses and defense against certain pathogens.Recent evidence obtained from using in vitro fungal cultures exposed to exogenous ET suggested that ET may regulate the production of aflatoxin by Aspergilli.However,the function of endogenous,seed-derived ET has not been explored.To understand the role of endogenous ET in modulating the immunity to Aspergillus flavus in maize,ET biosynthetic mutants,of ACC synthesases,acs2 and acs6,were inoculated with A.flavus.The results showed that each acs single mutant kernels displayed enhanced seed colonization and conidiation,but not the levels of aflatoxin,upon infection with A.flavus.Moreover,ET production is induced in the acs mutants infected with A.flavus.The expression of both ACS2 and ACS6 was moderately increased in WT seed upon A.flavus infection,while ACS2 expression,was strongly induced to a much higher levels in the acs6 mutant compared to that in WT seeds,at 4 dpi.Similarly,in the acs2 mutant seed,ACS6 expression was induced to a higher level upon infection,compared to that in WT seed,at 4 dpi.Thus,the increased ET in single mutants was likely due to the overexpression of functional ACS genes in response to A.flavus infection. |
PDF Full Text Request