Overexpression of MeH1.2 gene inhibited plant growth and increased branch root differentiation in transgenic cassava

Abstract

AbstractCassava (Manihot esculenta) is an important tropical crop with extraordinary tolerance to drought stress. Under drought stress, the histone H1 (named MeH1.2) protein of cassava leaf is significantly induced. In this study, the MeH1.2 gene was cloned from cassava to investigate the role of MeH1.2 protein in transcriptional regulation during the development of a multicellular organism in vivo. The MeH1.2 protein was localized to the cell nucleus. The expression of MeH1.2 gene was induced by polyethylene glycol, abscisic acid, and drought stress. Transgenic cassava overexpressing MeH1.2 gene (HOE) was generated from wild type cv.60444 (WT) by Agrobacterium‐mediated transformation. The 60‐d‐old HOE seedlings were significantly smaller and weaker than the WT in Murashige and Skoog medium. Moreover, they exhibited yellow leaves and senescence, and the number of branch roots increased significantly. We found a total of 1,670 down‐regulated differentially expressed genes (DEGs) and 891 up‐regulated DEGs in HOE leaves as indicated by RNA‐seq. Many DEGs were associated with metabolism and stress response, such as amino acid metabolic genes, wound‐responsive family genes, and peroxidase superfamily genes. We hypothesized that MeH1.2 overexpression may retard the growth of HOE plants. The increased proline content and root/shoot ratio of HOE seedlings also supported this hypothesis. Our findings will provide an important basis for further research on the function of the H1.2 gene and its role in drought resistance of cassava.