Overexpression of Os BOR1, a rice efflux boron transporter gene improved xylem loading of boron and grain yields in rice under the boron deficient condition

Abstract

In rice, a boron efflux transporter OsBOR1 mediates efficient boron translocation from root to shoot. We herein generated three independent lines of transgenic rice plants expressing rice BOR1-GFP under the control of the cauliflower mosaic virus 35S RNA promoter. Real-time RT-PCR analysis showed that BOR1-GFP was highly expressed in two out of the three lines and was slightly expressed in the other line. The boron concentration in xylem sap was 1.8-1.9 times higher in two lines over-expressing BOR1-GFP than in non-transgenic plants. The grain yields under the boron deficient condition was 1.7-1.8 times greater in two over-expressing lines than in non-transgenic plants and another transgenic line with slight expression. These results suggest that enhanced expression of the rice boron transporter BOR1 enhanced root-to-shoot translocation of boron, which resulted in improved grain yields under boron deficient condition.