Pepper CaMLO6 Negatively Regulates Ralstonia solanacearum Resistance and Positively Regulates High Temperature and High Humidity Responses.
Plant mildew-resistance locus O (MLO) proteins influence susceptibility to powdery mildew. However, their roles in plant responses to other pathogens and heat stress remain unclear. Here, we showed that CaMLO6, a pepper (Capsicum annuum) member of MLO clade V, is a protein targeted to plasma membrane and probably endoplasmic reticulum. The transcript expression level of CaMLO6 was upregulated in the roots and leaves of pepper plants challenged with high temperature and high humidity (HTHH) and was upregulated in leaves but downregulated in roots of plants infected with the bacterial pathogen Ralstonia solanacearum. CaMLO6 was also directly upregulated by CaWRKY40 upon HTHH but downregulated by CaWRKY40 upon R. solanacearum infection. Virus-induced gene silencing of CaMLO6 significantly decreased pepper HTHH tolerance and R. solanacearum susceptibility. Moreover, CaMLO6 overexpression enhanced the susceptibility of Nicotiana benthamiana and pepper plants to R. solanacearum and their tolerance to HTHH, effects that were associated with the expression of immunity- and thermotolerance-associated marker genes, respectively. These results suggest that CaMLO6 acts as a positive regulator in response to HTHH but a negative regulator in response to R. solanacearum. Moreover, CaMLO6 is transcriptionally affected by R. solanacearum and HTHH; these transcriptional responses are at least partially regulated by CaWRKY40.
['Yang|Sheng|S|', 'Shi|Yuanyuan|Y|', 'Zou|Longyun|L|', 'Huang|Jinfeng|J|', 'Shen|Lei|L|', 'Wang|Yuzhu|Y|', 'Guan|Deyi|D|', 'He|Shuilin|S|']
D002212:Capsicum D060467:Disease Resistance D018506:Gene Expression Regulation, Plant D018869:Heat-Shock Response D006813:Humidity D010935:Plant Diseases D010940:Plant Proteins D030821:Plants, Genetically Modified D011401:Promoter Regions, Genetic D043368:Ralstonia solanacearum D060888:Real-Time Polymerase Chain Reaction D014026:Tobacco D014157:Transcription Factors
CaMLO6 Ralstonia solanacearum Capsicum annuum CaWRKY40 High temperature–high humidity