Overexpression of a wheat phospholipase D gene, TaPLDα, enhances tolerance to drought and osmotic stress in Arabidopsis thaliana

Phospholipase D (PLD) is crucial for plant responses to stress and signal transduction, however, the regulatory mechanism of PLD in abiotic stress is not completely understood; especially, in crops. In this study, we isolated a gene, TaPLD alpha, from common wheat (Triticum aestivum L.). Analysis of the amino acid sequence of TaPLD alpha revealed a highly conserved C2 domain and two characteristic HKD motifs, which is similar to other known PLD family genes. Further characterization revealed that TaPLD alpha expressed differentially in various organs, such as roots, stems, leaves and spikelets of wheat. After treatment with abscisic acid (ABA), methyl jasmonate, dehydration, polyethylene glycol and NaCl, the expression of TaPLD alpha was up-regulated in shoots. Subsequently, we generated TaPLD alpha-overexpressing transgenic Arabidopsis lines under the control of the dexamethasone-inducible 35S promoter. The overexpression of TaPLD alpha in Arabidopsis resulted in significantly enhanced tolerance to drought, as shown by reduced chlorosis and leaf water loss, higher relative water content and lower relative electrolyte leakage than the wild type. Moreover, the TaPLD alpha-overexpressing plants exhibited longer roots in response to mannitol treatment. In addition, the seeds of TaPLD alpha-overexpressing plants showed hypersensitivity to ABA and osmotic stress. Under dehydration, the expression of several stress-related genes, RD29A, RD29B, KIN1 and RAB18, was up-regulated to a higher level in TaPLD alpha-overexpressing plants than in wild type. Taken together, our results indicated that TaPLD alpha can enhance tolerance to drought and osmotic stress in Arabidopsis and represents a potential candidate gene to enhance stress tolerance in crops.