Reception of and response to exogenous and endogenous osmotic changes is important to sustain plant growth and development, as well as reproductive formation. Hyperosmolality-gated calcium-permeable channels (OSCA) were first characterised as an osmosensor in Arabidopsis and are involved in the perception of extracellular changes to trigger hyperosmolality-induced [Ca2+]i increases (OICI). To explore the potential biological functions of OSCAs in rice, we performed a bioinformatics and expression analysis of the OsOSCA gene family. A total of 11 OsOSCA genes were identified from the genome database of Oryza sativa L. Japonica. Based on their sequence composition and phylogenetic relationship, the OsOSCA family was classified into four clades. Gene and protein structure analysis indicated that the 11 OsOSCAs shared similar structures with their homologs in Oryza sativa L. ssp. Indica, Oryza glaberrima, and Oryza brachyantha. Multiple sequence alignment analysis revealed a conserved DUF221 domain in these members, in which the first three TMs were conserved, while the others were not. The expression profiles of OsOSCA genes were analysed at different stages of vegetative growth, reproductive development, and under osmotic-associated abiotic stresses. We found that four and six OsOSCA genes showed a clear correlation between the expression profile and osmotic changes during caryopsis development and seed imbibition, respectively. Orchestrated transcription of three OsOSCAs was strongly associated with the circadian clock. Moreover, osmotic-related abiotic stress differentially induced the expression of 10 genes. The entire OSCA family is characterised by the presence of a conserved DUF221 domain, which functions as an osmotic-sensing calcium channel. The phylogenetic tree of OSCA genes showed that two subspecies of cultivated rice, Oryza sativa L. ssp. Japonica and Oryza sativa L. ssp. Indica, are more closely related than wild rice Oryza glaberrima, while Oryza brachyantha was less closely related. OsOSCA expression is organ- and tissue-specific and regulated by different osmotic-related abiotic stresses in rice. These findings will facilitate further research in this gene family and provide potential target genes for generation of genetically modified osmotic-stress-resistant plants.

OSCA (reduced hyperosmolality-induced [Ca²⁺]_i increase) is a family of mechanosensitive calcium-permeable channels that play a role in osmosensing and stomatal immunity in plants. Oryza sativa has 11 OsOSCA genes; some of these were shown to complement hyperosmolality-induced [Ca²⁺]_cyt increases (OICI_cyt), salt stress-induced [Ca²⁺]_cyt increases (SICI_cyt), and the associated growth phenotype in the Arabidopsis thaliana mutant osca1. However, their biological functions in rice remain unclear. In this paper, we found that OsOSCA1.1 mediates OICI_cyt and SICI_cyt 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_cyt and SICI_cyt were abolished in the roots of 10-day-old ososca1.1 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 ososca1.1 mutant, resulting in lower stomatal resistance and survival rates than that in ZH11. However, overexpression of OsOSCA1.1 in ososca1.1 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 Cis-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.

Bacillus subtilis strain Z15 (BS-Z15) was isolated from the cotton field of Xinjiang, China, and characterized as an effective biocontrol agent antagonizing plant pathogen Verticillium dahliae 991 (VD-991). However, the chemical substance produced by BS-Z15 for resistance to VD-991 remains elusive. Here, a serial purification methods including HCl precipitation, organic solvent extraction, and separation by semi-preparative High-Performance Liquid Chromatography were performed to obtain a single compound about 3.5 mg/L from the fermentation broth of BS-Z15, which has an antifungal activity against VD-991. Moreover, Fourier Transform Infrared spectrum, Nuclear Magnetic Resonance Spectroscopy, and Tandem Mass Spectrometry analyses were carried out to finally confirm that the active compound from BS-Z15 is a mycosubtilin homologue with C17 fatty acid chain. Genomic sequence prediction and PCR verification further showed that the BS-Z15 genome contains the whole mycosubtilin operon comprising four ORFs: fenF, mycA, mycB, and mycC, and the expression levels of mycA-N, mycB-Y and mycC-N reached a peak at 32-h fermentation. Although mycosubtilin homologue at 1 μg/mL promoted the germination of cotton seed, that with high concentration at 10 μg/mL had no significant effect on seed germination, plant height and dry weight. Furthermore, mycosubtilin homologue sprayed at 10 μg/mL on two-week-old cotton leaves promotes the expression of pathogen-associated genes and gossypol accumulation, and greatly decreases VD-991 infection in cotton with disease index statistics. This study provides an efficient purification strategy for mycosubtilin homologue from BS-Z15, which can potentially be used as a biocontrol agent for controlling verticillium wilt in cotton.