苹果属野生种特有基因SMR2在干旱胁迫中的功能分析

苹果属野生资源在抗旱方面具有明显的优势；核内复制（endo-replication）对细胞生长分化、应激响应起关键作用，但其抗逆机制有待研究。我们前期通过分析苹果野生种和栽培种的高质量基因组，确定一个野生苹果特有的核内复制调控基因SMR2，干旱和ABA处理下该基因在新疆野苹果中上调表达。为进一步研究其功能，本项目拟开展如下研究：以核心野生苹果资源为材料，分析SMR2直系同源基因的进化关系，研究其不同组织器官中响应干旱、激素等处理的转录表达模式，明确蛋白序列与功能分化的关系；通过对过表达SMR2的苹果植株的形态特征和生理生化指标测定，研究该基因在干旱胁迫下对根系形态、叶片形态和光合作用的调控效应；通过互作筛选、转录组测序、基因共表达网络分析，初步解析该基因所参与的调控网络和作用机制。研究成果将加深对野生苹果特有的耐旱相关基因及其耐旱分子机制的认识，也为栽培苹果的抗逆遗传改良提供新的基因资源。

The wild resources of Malus have obvious advantages in drought resistance. Endo-replication plays a key role in cell growth and differentiation and stress response. However, its regulative mechanism under stress tolerance has been largely unknown. Through a comparative analysis of high-quality wild and cultivated apple genomes, we found a wild apple-specific gene SMR2, which has been known for its role in promoting endo-replication. The expression of Malus sieversii MsSMR2 gene increased in response to drought and ABA. To further study its function, this project intends to carry out the following researches: first, phylogenetic analysis of the SMR2 orthologous genes from core wild apple genetic resources, followed by transcriptional expression analysis from different tissues under drought and hormone treatments. This can help us to clarify the relationship between protein sequence characteristics and functional differentiations. Second, in order to understand the regulative function of SMR2 on root morphology, leaf morphology, and photosynthesis under drought stress, we will overexpress this gene in cultivated apple and measure the changes in morphological characteristics and physiological and biochemical indexes. Lastly, using protein-protein interaction, transcriptome, and gene co-expression network analysis, we aim to gain insights of the regulatory network and mechanism that SMR2 has involved. Our results will not only deepen the understanding of the molecular function of the wild apple-specific drought-responsive genes, but also provide new genetic resources for genetic improvement of stress tolerance in cultivated apples.