S5H/DMR6 Encodes a Salicylic Acid 5-Hydroxylase That Fine-Tunes Salicylic Acid Homeostasis
作者单位：Institute of Plant Genetics and Developmental BiologyCollege of Chemistry and Life SciencesZhejiang Normal University
会议名称：《2018全国植物生物学大会》
会议日期：2018年
学科分类：0710[理学-生物学] 071001[理学-植物学] 07[理学]
关 键 词：2,5-Dihydroxybenzoic acid salicylic acid At5g24530 Salicylic Acid Homeostasis
摘 要：The phytohormone salicylic acid(SA) plays essential roles in biotic and abiotic responses,plant development,and leaf senescence.2,5-Dihydroxybenzoic acid(2,5-DHBA or gentisic acid) is one of the most commonly occurring aromatic acids in green plants and is assumed to be generated from SA,but the enzymes involved in its production remain ***6(Downy Mildew Resistant 6,At5 g24530) has been proven essential in plant immunity of Arabidopsis,but its biochemical properties are not well ***,we report the discovery and functional characterization of DMR6 as a SA 5-hydroxylase(S5 H) that catalyzes the formation of 2,5-DHBA by hydroxylating SA at the C5 position of its phenyl ring in Arabidopsis.S5 H/DMR6 specifically converts SA to 2,5-DHBA in vitro and displays higher catalytic efficiency(K/K=4.96×l0 Ms) than the previously reported SA 3-hydroxylase(S3 H,K/K=6.09×10 Ms) for ***,S5 H/DMR6 displays a substrate inhibition property that may enable automatic control of its enzyme *** s5 h mutant and s5 hs3 h double mutant over accumulate SA and display phenotypes such as a smaller growth size,early senescence and a loss of susceptibility to Pseudomonas syringae *** DC3000(Pst DC3000).S5 H/DMR6 is sensitively induced by SA/pathogen treatment and is widely expressed from young seedlings to senescing plants,whereas S3 H is more specifically expressed at the mature and senescing ***,our results disclose the identity of the enzyme required for 2,5-DHBA formation and reveal a mechanism by which plants fine-tune SA homeostasis by mediating SA 5-hydroxylation.