水稻是我国非常重要的主食作物，也是世界三大粮食作物之一。干旱和盐胁迫是两种主要的非生物胁迫，严重限制和影响水稻的质量和产量。二者具有共同的渗透胁迫信号，又有特定的胁迫响应，如分别对渗透物质与盐离子响应。因此，研究并解析水稻对干旱和盐胁迫的感知及应答机制具有非常重要的意义。OSCA（reduced hyperosmolality induced [Ca²⁺]_i increase）家族是一类机械敏感型钙透过离子通道。其中拟南芥OSCA1.1介导高渗诱导的胞内Ca²⁺浓度上升（OICI_cyt），OSCA1.3介导flg22引起的胞内Ca²⁺增加以调节气孔免疫。实验室前期对水稻OsOSCAs研究表明，OsOSCA家族有11个成员。其中OsOSCA1.4是一个质膜定位的离子通道，在HEK293细胞和拟南芥突变体osca1中介导OICI_cyt和SICI_cyt（高盐引起的[Ca²⁺]_cyt增加）；OsOSCA1.1介导水稻幼苗根系OICI_cyt和SICI_cyt，并且在水稻突变体ososca1.1中过表达OsOSCA1.1得到的回补株系，可以恢复高渗和高盐引起的气孔关闭受损及存活率极低的表型。然而，如何在分子水平解析高渗与盐胁迫介导的基因表达关系仍然是亟待解决的科学问题。本研究以四叶期的水稻野生型（ZH11）和ososca1.1用250 mM sorbitol和125 mM NaCl处理0和24 h后的材料为研究对象，通过高通量测序及转录组水平的关联分析，探索高渗和高盐胁迫条件下OsOSCA1.1介导水稻地上部分和地下部分的基因表达变化，以此解析OsOSCA1.1介导的钙信号在高渗与高盐胁迫响应中的基因表达调控网络。主要结果如下：

首先，对四叶期水稻地上部分的基因表达谱数据进行分析，共挖掘出6609个OsOSCA1.1调控的三类基因：2416个渗透物质响应基因，2349个盐离子响应基因和1844个渗透胁迫信号响应基因。GO富集分析结果显示，这三类基因均相对富集在“转录调控”、“激素响应”及“磷酸化”等生物学过程中；对部分OsOSCA1.1调控的基因提取启动子上游2000 bp的序列，显示富集到顺式作用元件ABRE、ARE、MYB和MYC转录因子结合位点等结合基序，与GO富集的结果基本一致。

同样地，对四叶期水稻地下部分的基因表达谱数据进行分析，共挖掘出6034个OsOSCA1.1调控的三类基因：1837个渗透物质响应基因，3505个盐离子响应基因和692个渗透胁迫信号响应基因。其次，对OsOSCA1.1介导的四叶期水稻地上部分和地下部分的高渗和高盐胁迫响应基因进行联合分析，分别发现水稻地上部分特异表达基因：1669个渗透物质响应基因、1668个盐离子响应基因及1195个渗透胁迫信号响应基因；地下部分特异表达基因：1060个渗透物质响应基因、2465个盐离子响应基因及432个渗透胁迫信号响应基因；地上和地下部分共同表达基因：249个渗透物质响应基因，359个盐离子响应基因和69个渗透胁迫信号响应基因。对OsOSCA1.1介导的地上部分和地下部分渗透物质响应基因和盐离子响应基因进行功能分析，四个部分均富集到了跟“刺激”相关的term，也有一些基因特异地分布在其他的term中，有关的基因在不同时期和不同的组织中明显特异性表达。进一步对OsOSCA1.1介导的地上部分和地下部分差异表达基因进行WGCNA（weighted gene co-expression network analysis）分析，其中与激素、激酶和重要的转录因子相关的基因共挖掘出31个，同时对其组分和功能进行了详尽的注释。以上结果暗示，OsOSCA1.1介导的钙信号是水稻感知高渗和高盐胁迫所必需的，其特异调控水稻干旱和盐胁迫下的基因表达，并在地上部分和地下部分表现出重叠和各自独特的特征，暗示OsOSCA介导的渗透和盐胁迫信号的长距离传递有重叠和各自独特的特征。

Rice is a very important staple food in our country and one of the world’s three major food crops. Drought and salt stress are two major abiotic stresses, which seriously limit and affect the quality and yield of rice. The common osmotic stress signal and unique stress response are involved in both drought and salt stresses. Therefore, it is greatly significant to study the molecular mechanisms on perception of and responses to drought and salt stresses in rice. The OSCA (reduced hyperosmolality induced [Ca²⁺]_i increase) has been demonstrated to be a type of mechanically sensitive Ca²⁺ permeation channel. In Arabidopsis, OSCA1.1 mediates hyperosmolality-induced [Ca²⁺]_cyt increases (OICI_cyt), and OSCA1.3 regulates stomatal immunity via mediating an increase in intracellular Ca²⁺ induced by flg22. Previous studies in our laboratory showed that rice genome includes multiple members of OsOSCAs, in which OsOSCA1.4 is a plasma-membrane-localized ion channel mediating OICI_cyt and SICI_cyt in HEK293 cells and Arabidopsis mutant osca1. Moreover, OsOSCA1.1 mediated OICI_cyt and SICI_cyt in rice seedling roots, and overexpression of OsOSCA1.1 in ososca1.1 rescues the impaired stomatal closure and very low survival rate caused by hyperosmolality and salt stresses. However, to distinguish the gene expression network response to hyperosmolality and salt stresses in rice is still elusive. In this study, four-leaf-stage wild type (ZH11) and ososca1.1 rice were treated with 250 mM sorbitol and 125 mM NaCl for 0 and 24 h, respectively. Then, transcriptome association analysis was performed to study the OsOSCA1.1-mediated gene expression network in the shoots and roots response to hyperosmolality and salt stresses. The main results are as follows:

Firstly, transcriptomic analysis in the shoots revealed the three types of 6609 OsOSCA1.1-regulated hyperosmolality- and salt-stress response genes: 2416 sorbitol-responsive, 2349 NaCl-responsive and 1844 common osmotic stress-responsive genes. The Gene Ontology enrichment analysis showed that these three types of OsOSCA1.1-regulated genes were relatively enriched in transcription regulation, hormone response, and phosphorylation terms of the biological processes category, which is consistent with the cis-regulatory elements ABRE, ARE, MYB and MYC binding motifs that were overrepresented in 2000-bp promoter regions of these OsOSCA1.1-regulated genes.

Similarly, transcriptomic analysis in the roots revealed the three types of 6034 OsOSCA1.1-regulated hyperosmolality- and salt-stress response genes: 1837 sorbitol-responsive, 3505 NaCl-responsive and 692 common osmotic stress-responsive genes. Secondly, the OSOSCA1.1-mediated genes response to hyperosmolality- and salt-stress in the shoots and roots of four-leaf-stage rice were jointly analyzed. We individually found that 1669 sorbitol-responsive, 1668 NaCl-responsive and 1195 common osmotic stress-responsive genes genes in the shoots, 1060 sorbitol-responsive, 2465 NaCl-responsive and 432 common osmotic stress-responsive genes in the roots, and the commonly expressed genes in shoots and roots: 249 sorbitol-responsive, 359 NaCl-responsive and 69 osmotic stress-responsive genes. The functional analysis of these commonly expressed genes in the shoots and roots revealed that the terms related to stimuli were enriched, and some genes were in specific terms of genes significantly and specifically enriched in different stages and different tissues. Furthermore, WGCNA (weighted gene co-expression network analysis) showed that 31 genes related to hormone, kinases and important TFs enriched in these differentially expressed genes in the shoots and roots. These results suggested that OsOSCA1.1-mediated calcium signaling is essential for rice to sense hyperosmolality and salt stresses, and OsOSCA1.1-mediating calcium signal pathway specifically regulates gene expression response to hyperosmolality and salt stresses, with overlapping and distinct characteristics in the shoots and roots, indicating that the long distance transduction of OsOSCA-mediated hyperosmolality- and salt-stress signals has overlapping and unique characteristics.