68. イネのブラシノステロイド誘導性bHLH型転写因子BU17はBRのシグナル伝達の抑制を介して下位節間や種子の伸長を抑制する(口頭発表,植物化学調節学会第46回大会)

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We have been studying the roles of two BR-inducible bHLH proteins, BUl and BU17, in rice. Previously we showed that BU1 is a positive regulator of BR signaling that controls lamina joint inclination in rice (Tanaka et al., 2009). On the other hand, BU1 7:OX plants showed BL-insensitive erect-leaf phenotype without decreasing the expression of BR biosynthetic genes. Therefore BU17 is presumed to be a negative regulator of BR signaling. In this work, we studied the loss of function phenotype of BU17 by RNAi-based knockdown and the expression pattern of BU17 by using RT-PCR and GUS-reporter plants. First, we made transgenic rice plants overexpressing BU17-like1 encoding a bHLH protein with highest similarity to BU17 in rice. Unlike BU17:OX plants, BU17-like1:OX plants did not repress lamina joint bending. This result suggested that BU17-like1 is not functionally redundant with BU17. Therefore we made RNAi- knockdown plants down-regulating BU17 alone. Unexpectedly, the BU17-kd plants did not enhance lamina joint inclination. However, the BU17-kd plants resembled BU1:OX plants that enhance BR-signaling with respect to the elongation of lower internodes and the enlargement of seed size. Promoter-GUS and RT-PCR analyses revealed that BU17 was expressed in leaf sheath, lamina joint, internodes, spikelets and rachis branches. These results suggest that BU17 is a negative regulator of BR signaling that mainly represses elongation of seeds and lower internodes of culm in rice.
2011-10-03

68. イネのブラシノステロイド誘導性bHLH型転写因子BU17はBRのシグナル伝達の抑制を介して下位節間や種子の伸長を抑制する(口頭発表,植物化学調節学会第46回大会)

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