Overexpression of TaLEA3 induces rapid stomatal closure under drought stress in Phellodendron amurense Rupr

Late embryogenesis abundant (LEA) proteins participate in drought stress responses in plants. In the present study, the gene TaLEA3 from the drought-resistant plant Tamarix androssowii was transformed into Amur cork tree (Phellodendron amurense) via Agrobacterium tumefaciens to investigate the mechanism of stomatal closure in response to osmotic stress. Our results showed that P. amurense overexpressing TaLEA3 were resistant to drought stress by rapid stomatal closure. To study the stomatal movement regulated at the molecular level, a model system for stoma closure was established in in vitro P. amurense. In this work, we found that the increased Ca²⁺ accumulation in guard cells of transgenic plants caused stomatal closure and activated K⁺ efflux under polyethylene glycol (PEG) stress. Moreover, H⁺ changes might provide a needed pH condition for stomatal closure. Further, nitric oxide (NO) fluorescence was measured using an NO-specific fluorescent probe, diaminofluorescein-FM diacetate, which showed that guard cell NO fluorescence was stronger in transgenic plants compared with wild type plants. Additionally, five genes encoding nitrate reductase were up-regulated, indicating that TaLEA3 overexpression positively regulated NO biosynthesis and accumulation in the guard cells. This discovery will further our understanding of the LEA gene function and will help in engineering drought-resistant tree cultivars.