The MAX2-KAI2 module promotes salicylic acid-mediated immune responses in Arabidopsis  

作　　者：Xiujuan Zheng Fangqian Liu Xianfeng Yang Weiqiang Li Sique Chen Xinwu Yue Qi Jia Xinli Sun 

机构地区：[1]Key Laboratory of Ministry of Education for Genetics,Breeding and Multiple Utilization of Crops,College of Agriculture,Fujian Agriculture&Forestry University,Fuzhou 350002,China [2]Jilin Da'an Agro-ecosystem National Observation Research Station,Key Laboratory of Mollisols Agroecology,Northeast Institute of Geography and Agroecology,Chinese Academy of Sciences,Changchun 130102,China

出　　处：《Journal of Integrative Plant Biology》2023年第6期1566-1584,共19页植物学报（英文版）

基　　金：supported by the Research Fund for the Doctoral Program of Higher Education of China(30123515110006);the National Natural Science Foundation of China(31371557 and 31571574);the China Postdoctoral Science Foundation(2014T70603 and 2013M540527)。

摘　　要：Arabidopsis MORE AXILLARY GROWTH2 MAX2)is a key component in the strigolactone(SL)and karrikin(KAR)signaling pathways and regulates the degradation of SUPPRESSOR OF MAX21/SMAX1-like(SMAX1/SMXL)proteins,which are transcriptional co-repressors that regulate plant architecture,as well as abiotic and biotic stress responses.The max2 mutation reduces resistance against Pseudomonas syringae pv.tomato(Pst).To uncover the mechanism of MAX2-mediated resistance,we evaluated the resistance of various SL and KAR signaling pathway mutants.The resistance of SL-deficient mutants and of dwarf 14(d14)was similar to that of the wild-type,whereas the resistance of the karrikin insensitive 2(kai2)mutant was compromised,demonstrating that the KAR signaling pathway,not the SL signaling pathway,positively regulates the immune response.We measured the resistance of smaxl and smxl mutants,as well as the double,triple,and quadruple mutants with max2,which revealed that both the smax1 mutant and smx16/7/8 triple mutant rescue the low resistance phenotype of max2 and that SMAX1 accumulation diminishes resistance.The susceptibility of smax1D,containing a degradation-insensitive form of SMAX1,further confirmed the SMAX1 function in the resistance.The relationship between the accumulation of SMAX1/SMXLs and disease resistance suggested that the inhibitory activity of SMAX1 to resistance requires SMXL6/7/8.Moreover,the exogenous application of KAR2 enhanced resistance against Pst,but KAR-induced resistance depended on salicylic acid(SA)signaling.Inhibition of karrikin signaling delayed SA-mediated defense responses and inhibited pathogen-induced protein biosynthesis.Together,we propose that the MAX2-KAI2-SMAX1 complex regulates resistance with the assistance of SMXL6/7/8 and SA signaling and that SMAX1/SMXLs possibly form a multimeric complex with their target transcription factors to fine tune immune responses.

关 键 词：degradation IMMUNITY karrikin pathway STRIGOLACTONE SMAX1/SMXLs transcription factor 

分 类 号：S432.2[农业科学—植物病理学]