Department of Plant Sciences

Boron is one of the essential elements for plant growth and development and its deficiency is known to reduce quantity and quality of agricultural products. In this study, we evaluated the effect of boron limitation on the growth and yields of rice plants using hydroponic culture system. Boron limitation did not affect the plant height of young seedlings, but prolonged limitation of boron clearly reduced the plant height under 0.18 µM boron treatments. Moreover, yields of rice grains were severely impaired under 0.18 µM boron treatments, because of inhibited panicle formation and following reduced spikelet numbers. As a next step, we generated transgenic rice plants expressing rice BOR1-GFP to engineer the crop tolerant to boron limited condition. OsBOR1, a boron efflux transporter in rice mediates efficient boron translocation from root to shoot. Thus generated overexpressors were expected to show enhanced root-to-shoot boron transport. We established 11 independent lines and confirmed the expression of introduced gene in several lines. The initial growth of transgenic plants under boron limitation did not differ among the lines and NT. However, boron concentration in xylem sap was higher in some transgenic lines than NT and transgenic lines not expressing introduced gene. These results suggest that the major boron deficient symptom in rice is impaired development of reproductive tissues and up-regulation of boron transporter has the potential in improving boron acquisition into shoots under boron limited condition.