Expression profile of MYB60 and GUSP1 genes during early growth of cotton genotypes submitted to water stress

Cotton has high adaptability to adverse conditions; however, one of the main factors causing production loss is water deficits. To adapt to these conditions, plants go through a series of changes, many of them driven by genes that are expressed to increase drought tolerance. We examined the expression profile of the MYB60 and GUSP1 genes, which are involved in the abiotic stress pathway, focusing on drought tolerance. Four Upland and Moco genotypes were submitted to water stress during early growth and further evaluated at 50% (phase 1) and 80% (phase 2) of stomata enclosure. Plants were previously phenotyped, based on vegetative, physiological and biochemical traits. Expression of GUSP1 and MYB60 transcripts was estimated by qRT-PCR. Plants were grown in 288 mL pots in a greenhouse and further submitted to water stress during 25 days. Although Moco cotton is considered tolerant to drought and upland cotton is known to be drought-sensitive; we found a different behavior in these genotypes. Moco 1 was very sensitive to the imposed water deficiency stress, with severe reductions in leaf number, stem diameter and weight of roots and canopy, while Delta Opal (Upland) presented the smallest reductions in growth. Expression of GUSP1 transcripts was higher in all stressed genotypes, in both phases, during the water stress period, with the genotype Moco 2, presenting the highest level of expression, while MYB60 transcripts were high expressed only in phase 1, decreasing in phase 2. Considering that differences in the expression of MYB60 can be detected earlier, because the peak of expression occurred at phase 1 of water stress, it is worth investigating the genetic diversity in cotton germplasm to select genotypes with drought tolerance and to estimate the relation with the expression of MYB60, since Moco genotypes were considered tolerant, but in this work a Moco 1 genotype presented drought-sensitive characteristics.