Stress-inducible expression of barley Hva1 gene in transgenic mulberry displays enhanced tolerance against drought, salinity and cold stress

Abstract

Coping with different kinds of biotic and abiotic stresses is the foundation of sustainable agriculture. Although conventional breeding and marker-assisted selection are being employed in mulberry (Morus indica L.) to develop better varieties, nonetheless the longer time periods required for these approaches necessitates the use of precise biotechnological approaches for sustainable agriculture. In an attempt to improve stress tolerance of mulberry, an important plant of the sericulture industry, an encoding late embryogenesis abundant gene from barley (HVA1) was introduced into mulberry plants by Agrobacterium-mediated transformation. Transgenic mulberry with barley Hva1 under a constitutive promoter actin1 was shown to enhance drought and salinity tolerance. Here, we report that overexpression of barley Hva1 also confers cold tolerance in transgenic mulberry. Further, barley Hva1 gene under control of a stress-inducible promoter rd29A can effectively negate growth retardation under non-stress conditions and confer stress tolerance in transgenic mulberry. Transgenic lines display normal morphology to enhanced growth and an increased tolerance against drought, salt and cold conditions as measured by free proline, membrane stability index and PSII activity. Protein accumulation was detected under stress conditions confirming inductive expression of HVA1 in transgenics. Investigations to assess stress tolerance of these plants under field conditions revealed an overall better performance than the non-transgenic plants. Enhanced expression of stress responsive genes such as Mi dnaJ and Mi 2-cysperoxidin suggests that Hva1 can regulate downstream genes associated with providing abiotic stress tolerance. The investigation of transgenic lines presented here demonstrates the acquisition of tolerance against drought, salt and cold stress in plants overexpressing barley Hva1, indicating that Arabidopsis rd29A promoter can function in mulberry.