LEA 4 group genes from the resurrection plant Boea hygrometrica confer dehydration tolerance in transgenic tobacco

The resurrection plant Boea hygrometrica can survive extreme dehydration and is used as a model system to study desiccation tolerance. Screening of a cDNA library prepared from desiccated leaves via a macroarray technique has resulted in the identification of two dehydration responsive genes that encode group 4 late embryogenesis abundant (LEA) proteins, designated as BhLEA1 and BhLEA2, respectively. BhLEA1 and BhLEA2 were induced by dehydration and signaling molecules, including abscisic acid (ABA). Transgenic tobacco that ectopically express BhLEA1 and BhLEA2 were generated and used to study the role of LEA proteins in dehydration tolerance. After a period of drought, the relative water content of leaves and photosystem II activity in transgenic tobacco were higher than wild-type plants. Furthermore the membrane permeability was lower in selected transgenic lines that expressed BhLEA1 and BhLEA2 than in wild-type plants. Superoxide dismutase and peroxidase activities were increased in transgenic plants relative to that observed in the wild-type control and proteins including ribulose-bisphosphate carboxylase (large subunit), light-harvesting complex II and photosystem II extrinsic protein were stabilized in transgenic plants compared to wild-type plants. Surprisingly, the steady state levels of BhLEA1 and BhLEA2 protein substantially increased in response drying, despite being under the transcriptional control of the CaMV 35S promoter. Data presented here suggests that BhLEA genes are likely to play a role in the general protection of the plant cell during dehydration and affect membrane and protein stability.