| Resumo: | OSCA (<i>reduced hyperosmolality-induced [Ca<sup>2+</sup>]<sub>i</sub> increase</i>) is a family of mechanosensitive calcium-permeable channels that play a role in osmosensing and stomatal immunity in plants. <i>Oryza sativa</i> has 11 <i>OsOSCA</i> genes; some of these were shown to complement hyperosmolality-induced [Ca<sup>2+</sup>]<sub>cyt</sub> increases (OICI<sub>cyt</sub>), salt stress-induced [Ca<sup>2+</sup>]<sub>cyt</sub> increases (SICI<sub>cyt</sub>), and the associated growth phenotype in the <i>Arabidopsis thaliana</i> mutant <i>osca1</i>. However, their biological functions in rice remain unclear. In this paper, we found that OsOSCA1.1 mediates OICI<sub>cyt</sub> and SICI<sub>cyt</sub> in rice roots, which are critical for stomatal closure, plant survival, and gene expression in shoots, in response to hyperosmolality and the salt stress treatment of roots. Compared with wild-type (Zhonghua11, ZH11) plants, OICI<sub>cyt</sub> and SICI<sub>cyt</sub> were abolished in the roots of 10-day-old <i>ososca1.1</i> seedlings, in response to treatment with 250 mM of sorbitol and 100 mM of NaCl, respectively. Moreover, hyperosmolality- and salt stress-induced stomatal closure were also disrupted in a 30-day-old <i>ososca1.1</i> mutant, resulting in lower stomatal resistance and survival rates than that in ZH11. However, overexpression of <i>OsOSCA1.1</i> in <i>ososca1.1</i> complemented stomatal movement and survival, in response to hyperosmolality and salt stress. The transcriptomic analysis further revealed the following three types of OsOSCA1.1-regulated genes in the shoots: 2416 sorbitol-responsive, 2349 NaCl-responsive and 1844 common osmotic stress-responsive genes after treated with 250 mM of sorbitol and 125 mM NaCl of in 30-day-old rice roots for 24 h. The Gene Ontology enrichment analysis showed that these 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 <i>Cis</i>-regulatory elements ABRE, ARE, MYB and MYC binding motifs that were overrepresented in 2000-bp promoter regions of these OsOSCA1.1-regulated genes. These results indicate that OsOSCA-mediated calcium signaling specifically regulates gene expression, in response to drought and salt stress in rice.
|
|---|