Expressão de variantes de aquaporinas em algodão submetido a estresse salino

Abstract

Salinization leads to several damages to agricultural regions at worldwide, especially in semiarid climate, reducing the crop yields. Cotton (Gossypium hirsutum L.) is a Malvaceae with wide genetic variability to salt stress. The identification of salinity tolerant genotypes in a breeding program is a dynamic target, due to selection is often based on plant phenotypes. Molecular markers are reliable tools to aid in these selection processes. It is known that aquaporins (AQPs) are channel proteins with a fundamental role in water relations and tolerance to environmental stresses. The plants have fine regulation of water transport through the activity of AQPs. In this work three AQP subtypes were adopted in order to evaluate the tolerance to saline stress, based on the expression of transcripts by qPCR. Additionally, physiological descriptors were adopted to validate the molecular findings. Seven cotton genotypes were subjected to saline stress (190 mM NaCl), initiated at V3 stage (21 days after emergence), during 72 h. At the end of stress, root tissues were collected for total RNA extraction, followed by cDNA synthesis and qPCR analyzes. At the same time, full expanded leaves were used to record the gas exchange, using IRGA, and measuring the relative water content. The dry matter of the shoots was also evaluated. Three sets of specific primers were used, drawn from NCBI sequences of GhPIP1;1, GhTIP2;1 and GhSIP1;3. The GhPP2A gene was used as a reference. From the expression pattern of the AQPs transcripts, we found that the genotypes adapted to semiarid (BRS Seridó, 7MH, CNPA MT 2009 152 and BRS 416) revealed down regulation of AQP subtypes, mainly GhPIP1;1 and GhTIP2;1 whose action are characterized as tolerance to salinity. The results of gas exchanges, relative water content and dry matter were consistent with the molecular ones, which are supported to confirm that GhPIP1;1 and GhTIP2;1 located at plasma membrane and vacuoles, respectively, could be adopted as markers for identification of cotton genotypes with tolerance to salinity.