SlMYC2 promotes SlLBD40‐mediated cell expansion in tomato fruit development

• Published in: The Plant journal : for cell and molecular biology 2024-06, Vol.118 (6), p.1872-1888
• Main Authors: Liu, Lun, Zhang, Jialong, Xu, Jiayi, Li, Yafei, Lv, Hongmei, Wang, Fei, Guo, Junxin, Lin, Tao, Zhao, Bing, Li, Xin‐Xu, Guo, Yang‐Dong, Zhang, Na
• Format: Article
• Language: English
• Subjects: cell expansion; Fruit - genetics; Fruit - growth & development; fruit size; Fruits; Gene Expression Regulation, Plant; Genetic analysis; Genetics; Jasmonic acid; Plant growth; Plant Proteins - genetics; Plant Proteins - metabolism; Plants, Genetically Modified; Promoter Regions, Genetic - genetics; protein interaction; Ripening; SlEXPA5; SlLBD40; SlMYC2; Solanum lycopersicum - genetics; Solanum lycopersicum - growth & development; Solanum lycopersicum - metabolism; tomato; Tomatoes; Transcription Factors - genetics; Transcription Factors - metabolism
• ISSN: 0960-7412; 1365-313X; 1365-313X
• DOI: 10.1111/tpj.16715

SUMMARY As a plant‐specific transcription factor, lateral organ boundaries domain (LBD) protein was reported to regulate plant growth and stress response, but the functional research of subfamily II genes is limited. SlMYC2, a master regulator of Jasmonic acid response, has been found to exhibit high expression levels in fruit and has been implicated in the regulation of fruit ripening and resistance to Botrytis. However, its role in fruit expansion remains unknown. In this study, we present evidence that a subfamily II member of LBD, namely SlLBD40, collaborates with SlMYC2 in the regulation of fruit expansion. Overexpression of SlLBD40 significantly promoted fruit growth by promoting mesocarp cell expansion, while knockout of SlLBD40 showed the opposite result. Similarly, SlMYC2 knockout resulted in a significant decrease in cell expansion within the fruit. Genetic analysis indicated that SlLBD40‐mediated cell expansion depends on the expression of SlMYC2. SlLBD40 bound to the promoter of SlEXPA5, an expansin gene, but did not activate its expression directly. While, the co‐expression of SlMYC2 and SlLBD40 significantly stimulated the activation of SlEXPA5, leading to an increase in fruit size. SlLBD40 interacted with SlMYC2 and enhanced the stability and abundance of SlMYC2. Furthermore, SlMYC2 directly targeted and activated the expression of SlLBD40, which is essential for SlLBD40‐mediated fruit expansion. In summary, our research elucidates the role of the interaction between SlLBD40 and SlMYC2 in promoting cell expansion in tomato fruits, thus providing novel insights into the molecular genetics underlying fruit growth. Significance Statement MYC2 is the master regulator of JA response which mainly functions in defense. Here, we found that SlMYC2 functions in fruit expansion, as it stimulates SlLBD40 expression and assists SlLBD40 in activating the expansin gene SlEXPA5, thereby promoting cell expansion.