Abstract
Drought stress is the main limiting factor of soybean yield. Currently, genetic engineering has been one important tool in the development of drought-tolerant cultivars. A widely used strategy is the fusion of genes that confer tolerance under the control of the CaMV35S constitutive promoter; however, stress-responsive promoters would constitute the best alternative to the generation of drought-tolerant crops. We characterized the promoter of α-galactosidase soybean (GlymaGAL) gene that was previously identified as highly up-regulated by drought stress. The β-glucuronidase (GUS) activity of Arabidopsis transgenic plants bearing 1000- and 2000-bp fragments of the GlymaGAL promoter fused to the uidA gene was evaluated under air-dried, polyethylene glycol (PEG) and salt stress treatments. After 24 h of air-dried and PEG treatments, the pGAL-2kb led to an increase in GUS expression in leaf and root samples when compared to the control samples. These results were corroborated by qPCR expression analysis of the uidA gene. The pGAL-1kb showed no difference in GUS activity between control and treated samples. The pGAL-2kb promoter was evaluated in transgenic soybean roots, leading to an increase in EGFP expression under air-dried treatment. Our data indicates that pGAL-2kb could be a useful tool in developing drought-tolerant cultivars by driving gene expression.
Highlights
Among the 13 different cis-acting elements identified as associated with the drought response, only the ABREATRD22 motif was not found in the GlymaGAL promoter
We evaluated the activity of pGAL-1kb and pGAL-2kb promoter sequences of the soybean a-galactosidase gene in Arabidopsis and soybean transgenic plants under drought and salt stress
The pGAL-2kb promoter sequence did not show a significant change in the activity of Arabidopsis transgenic plants under salt stress conditions (Figure 5)
Summary
The yield and production of soybean has been impacted by the occurrence of drought-stress. The loss of Brazilian soybean production was approximately 13% due to drought stress (Conab, 2012). The most severe drought stress period in Brazil occurred between 2003 and 2005, when the loss of soybean was greater than 20% of production (Polizel et al, 2011). The development of drought-tolerant soybean cultivars is crucial and should have high priority. The development of transgenic crops by the overexpression of drought-tolerant genes has been proven to be successful and can have a significant impact on agricultural production (Silvente et al, 2012; Rahman et al, 2016)
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