Characterization of Molecular and Physiological Responses Under Water Deficit of Genetically Modified Soybean Plants Overexpressing the AtAREB1 Transcription Factor

Abstract

Drought is one of the major factors limiting crop productivity worldwide. Currently, the techniques of genetic engineering are powerful tools for the development of drought-tolerant plants, once they allow for the modification of expression patterns of genes responsive to drought. Within this context, transcription factors recognize specific DNA sequences in the regulatory region of target genes, and thereby regulate their expression. AREB is a transcription factor in the basic leucine zipper family, which binds to the ABRE element in the promoter region of genes induced by abscisic acid and drought. In this study, soybean plants transformed with the 35S:AtAREB1 construct were submitted to drought under greenhouse conditions. AtAREB1 expression was observed in the transgenic lines 1Ea2939 and 1Eb2889, but not in the event 1Ea15 and, under control of the CaMV 35S promoter, did not cause dwarfism and resulted in a higher survival rate of transformed plants after drought and rehydration. Moreover, 1Ea2939 and 1Eb2889 plants presented a greater total number of pods and seeds and increased dry matter content of seeds. The best performance of the transgenic lines 1Ea2939 and 1Eb2889 relative to BR 16 plants (wild type) and to event 1Ea15 might be related to mechanisms of drought prevention through reduced stomatal conductance and leaf transpiration under control conditions. Changes in the expression profile of phosphatases and kinases may also be involved. Such results suggest that the constitutive overexpression of the transcription factor AtAREB1 leads to an improved capacity of the soybean crop to cope with drought with no yield losses.