Senescence is delayed when ramie (Boehmeria nivea L.) is transformed with the isopentyl transferase (ipt) gene under control of the SAG12 promoter

Ramie is an economically important industrial fiber crop widely planted in China, India, and other Southeast Asian and Pacific Rim countries. It plays an important role in China's economy, where ramie farming, industry, and trade provide livelihood support to about five million people. However, poor fiber production resulting from leaf senescence and leaf abscission is a significant problem. In this study, we report the successful production of transgenic ramie plants which delayed leaf senescence and enhanced biomass. Transgenic ramie plants were obtained via transformation with the Agrobacterium tumefaciens strain harboring the binary vector pSG529 containing the isopentyl transferase (ipt) gene under control of the SAG12 promoter (PSAG12-ipt construct). Agrobacterium tumefaciens strain EHA105 was used for the midrib explant transformation. The transformation frequency was 28.29%. Southern blot confirmed the integration of 1-4 copies of the NPTII gene into the ramie genome in the tested lines. At the fiber maturation stage, the transgenic plants had higher photosynthesis rates, chlorophyll content (SPAD values), and stronger resistance to exogenous ethylene compared with wild-type plants.