Annual Report 2003

50% shorter compared to the vector controlwhen they reach maturity, but no otherabnormal morphological changes wereobserved (Fig. 2). BL could not enhance itsexpression in transgenic rice expressing antisenseBRI1, which is a BR receptor, indicatingthat BR signaling to the enhancedexpression of OsBLE2 is through BRI1 (Fig.3A). BL effect in d1 mutant rice, which isdefective in alfa-subunit of heterotrimeric Gprotein, was much weaker than that in wildtype control (Fig. 3B). MAP kinase isinvolved in cell division and growth inplants. Its specific inhibitor, apiginin, couldinhibit the BL enhanced expression ofOsBLE2 (Fig. 3C). Thus, heterotrimeric Gprotein and MAP kinase may be componentsof BRs signaling. These results suggest thatOsBLE2 is involved in BL-regulated growthand development processes in rice.ControlOsBLE2antisenseHeight (cm)10080604020Control1_11_21_40 3 4 6 8 10 12 13 (Weeks)3.2 kbControl1-1OsBLE2rRNAFig. 2Construction of transgenic rice plant constitutively overexpressingthe antisense OsBLE2. Transgenic rice 3months after being transferred to soil in an isolation greenhouse and growth curves of 3 OsBLE2 antisense plantsand a vector control transgenic plant.1-21-4Fig. 3Exploring the BL signaling pathway leading to theOsBLE2 expression. Leaf sheaths of OsBRI1 antisensetransgenic rice (A) and d1 mutant (B) and their wild typeseedlings were treated with 1 µM BL for 12 h. Leafsheaths of wild type plants were treated with 1 µM BL inthe presence or absence of 500 µM MAP kinase inhibitorapiginin for 12 h (C). Total RNAs from the above sampleswere extracted and probed with full-length insert ofOsBLE2 EST.38 Annual Report 2003