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Salinity is a common abiotic stress that limits crop productivity. Although there is a wealth of evidence suggesting that miRNA and lncRNA play important roles in the response to salinity in rice seedlings and reproductive stages, the mechanism by which competing endogenous RNAs (ceRNAs) influence salt tolerance and yield in rice has been rarely reported. In this study, we conducted full whole-transcriptome sequencing of rice panicles during the reproductive period to clarify the role of ceRNAs in the salt stress response and yield. A total of 214 lncRNAs, 79 miRNAs, and 584 mRNAs were identified as differentially expressed RNAs under salt stress. Functional analysis indicates that they play important roles in GO terms such as response to stress, biosynthesis processes, abiotic stimuli, endogenous stimulus, and response to stimulus, as well as in KEGG pathways such as secondary metabolite biosynthesis, carotenoid biosynthesis, metabolic pathways, and phenylpropanoid biosynthesis. A ceRNA network comprising 95 lncRNA–miRNA–mRNA triplets was constructed. Two lncRNAs, MSTRG.51634.2 and MSTRG.48576.1, were predicted to bind to osa-miR172d-5p to regulate the expression of OsMYB2 and OsMADS63, which have been reported to affect salt tolerance and yield, respectively. Three lncRNAs, MSTRG.30876.1, MSTRG.44567.1, and MSTRG.49308.1, may bind to osa-miR5487 to further regulate the expression of a stress protein (LOC_Os07g48460) and an aquaporin protein (LOC_Os02g51110) to regulate the salt stress response. This study is helpful for understanding the underlying molecular mechanisms of ceRNA that drive the response of rice to salt stress and provide new genetic resources for salt-resistant rice breeding. [ABSTRACT FROM AUTHOR]

Salinity is an environmental stress that severely impacts rice grain yield and quality. However, limited information is available on the molecular mechanism by which salinity reduces grain quality. In this study, we investigated the milling, appearance, eating and cooking, and nutritional quality among three japonica rice cultivars grown either under moderate salinity with an electrical conductivity of 4 dS/m or under non-saline conditions in a paddy field in Dongying, Shandong, China. Moderate salinity affected rice appearance quality predominantly by increasing chalkiness rate and chalkiness degree and affected rice eating and cooking and nutritional quality predominantly by decreasing amylose content and increasing protein content. We compared the expression levels of genes determining grain chalkiness, amylose content, and protein content in developing seeds (0, 5, 10, 15, and 20 days after flowering) of plants grown under saline or non-saline conditions. The chalkiness-related gene Chalk5 was up-regulated and WHITE-CORE RATE 1 was repressed. The genes Nuclear factor Y and Wx, which determine amylose content, were downregulated, while protein-content-associated genes OsAAP6 and OsGluA2 were upregulated by salinity in the developing seeds. These findings suggest some target genes that may be utilized to improve the grain quality under salinity stress conditions via gene-pyramiding breeding approaches. [ABSTRACT FROM AUTHOR]

Identifying elite stress-tolerant varieties and elucidating the genetic mechanisms mediating stress resistance can help breeders develop and exploit new rice germplasm resources. In this study, we identified five salt-tolerant varieties and five drought-tolerant upland rice varieties by survival rate and drought tolerance grade and constructed variation maps of the resistance using a deep-sequencing approach. Using 116 rice accessions from the 3000 Rice Genomes Project, we characterized the population structure of sequenced varieties. Through comparative genomics and transcriptome analysis, we screened 39 salt-response candidate genes. Natural variation analysis on root length-related drought candidate gene showed that Hap1 and Hap4 were the predominant haplotypes in indica, while Hap5 was the predominant haplotype in japonica. Gene Ontology (GO) analysis showed that carbohydrate metabolic process, defense response, and response to stimulus were the common GO terms associated with salt and drought tolerance. Selective signatures in elite stress-tolerant varieties indicated that multiple important stress tolerance genes, namely OsRac1, Pikp-2, Xa26, OsSIRP4, and wsl1, were selected and utilized in these sequenced rice varieties. These findings may be useful for clarifying the genetic variations among elite stress-tolerant varieties, while also laying the foundation for a more comprehensive investigation of the genetic basis of salt and drought tolerance. [ABSTRACT FROM AUTHOR]