Caracterização de genes Whirly em acessos selvagens do gênero Oryza e resposta a salinidade e baixas temperaturas em arroz cultivado

Abstract

Unfavorable environmental conditions, such as salinity and low temperatures affect rice (Oryza sativa L.) produtivity. In Rio Grande do Sul state, the main rice growing region in Brazil, incidence of low temperatures results in significant yield losses. In addition, problems with salinity are common, as the source of the water for the irrigation in the field, especially in the Coastal Plain, comes from Laguna dos Patos, and depending on the monthly precipitation receives water from the Atlantic Ocean, which increases its salt content. The use of tolerant genotypes is one of the strategies to minimize the losses caused by abiotic stresses. The identification of genes involved in the tolerance response to abiotic stresses can help the development of new tolerant genotypes. The gene expression is essential in abiotic stress signaling, starting with the activation of transcription factors (TFs), which are linked to cis-acting regulatory elements (CREs), located in the promoter and other regulatory regions in genes involved in stress responses, activating a signaling cascate. The search for TFs involved in plant response to stresses is constant, and several researches have been conducted. However, there are few studies related to Whirly family. In this context, this study aimed at identify and characterize Whirly genes in species of Oryza genus and to investigate the role of these genes in rice seedlings submitted to low temperatures and salinity. The first study demonstrated that the Whirly genes are conserved in terms of number of copies and location in chromossomes among the species of Oryza genus. However, they have structural variations, that can be used as a source of genetic variability for stress tolerance. In addition, the promoter region of Whirly genes has CREs targeted by TFs DREB/CBF, AREB/ABF, MYB, MYC, WRKYs, which are involved in abiotic stress signaling. These results suggest that Whirly genes can be involved in low temperatures and salinity stress response in rice. The second study was performed using seedlings of BRS Pampa (sensitive) and BRS Bojuru (tolerant) cultivars submitted to low temperatures and salinity. In general, the studied stress condition leads to a transcriptional activation of Whirly2 and Whirly6 genes in the tolerant genotype. Whirly gene promotores differ in type and occurrences of CREs between the sensitive and tolerant cultivars. This finding may explain the difference in the transcript accumulation observed between them. The results found show the first insights in the involvement of Whirly genes in stress response signaling to salinity and low temperatures in rice seedlings.