Cassava (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.

中文翻译：

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MeH1.2基因过表达抑制转基因木薯植物生长并增加分枝根分化

木薯（Manihot esculenta）是一种重要的热带作物，对干旱胁迫具有非凡的耐受性。在干旱胁迫下，木薯叶组蛋白H1（命名为MeH1.2）蛋白被显着诱导。在这项研究中，从木薯中克隆了MeH1.2基因，以研究 MeH1.2 蛋白在体内多细胞生物发育过程中转录调控中的作用。MeH1.2 蛋白定位于细胞核。MeH1.2基因的表达受聚乙二醇、脱落酸和干旱胁迫诱导。过表达MeH1.2基因 (HOE) 的转基因木薯由农杆菌从野生型 cv.60444 (WT) 产生-介导的转化。在 Murashige 和 Skoog 培养基中，60 天龄的 HOE 幼苗比 WT 显着更小和更弱。此外，它们表现出黄叶和衰老，并且分枝根的数量显着增加。如RNA-seq所示，我们在HOE叶子中总共发现了1,670个下调的差异表达基因（DEG）和891个上调的DEG。许多DEG与代谢和应激反应有关，如氨基酸代谢基因、伤口反应家族基因和过氧化物酶超家族基因。我们假设MeH1.2过度表达可能会阻碍 HOE 植物的生长。HOE 幼苗的脯氨酸含量和根/芽比的增加也支持了这一假设。我们的研究结果将为进一步研究H1.2基因的功能及其在木薯抗旱中的作用提供重要依据。