Ectopic over-expression of ABA-responsive Chickpea galactinol synthase (CaGolS) gene results in improved tolerance to dehydration stress by modulating ROS scavenging

Abstract

Galactinol synthase (EC: 2.4.1.123) is a crucial enzyme of raffinose family oligosaccharides (RFO's) biosynthesis, essentially catalyzes the first crucial step in the raffinose biosynthetic pathway. Galactinol and raffinose accumulation along with its higher homologs such as stachyose and verbascose has been considered to participate in plant abiotic stress tolerance. Previously, we reported the function of chickpea galactinol synthase (CaGolS) genes in seed vigor and heat and oxidative stress tolerance. Here, we demonstrate the role and regulation of CaGolS in response to dehydration stress in chickpea. Through transcript accumulation and promoter-gus analyses, we demonstrate that the expression of CaGolS1 and CaGolS2 are positively influenced by dehydration stress and ABA treatment. Further, we have shown that the level of galactinol and raffinose are remarkably enhanced in response to dehydration stress and ABA. Utilizing CaGolS1 and CaGolS2 over-expression Arabidopsis lines, we demonstrate the role of CaGolS in dehydration stress tolerance. The biochemical and physiological analysis revealed that CaGolS over-expressing transgenic lines exhibited improved phenotype with respect to higher number of siliques, plant height, and rosette diameter under dehydration stress. The improved dehydration stress tolerance was corelated with higher chlorophyll retention and relative water content of transgenic lines. Further, lower H2O2, MDA content, and ion-leakage in transgenic lines suggest that CaGolS mediates dehydration stress tolerance by protecting the membrane damage from ROS attack. Collectively, our data highlight the prospect of CaGolS genes in improving dehydration stress tolerance in plants.