Abstract
Previously, we reported on the role of rice SHORT GRAIN 1 (SG1) gene in the control of organ size. SG1 is mainly expressed in roots and developing panicles. Overexpression of SG1 in rice caused a short grain and dwarf phenotype. In contrast, knockdown of SG1 and its homologue, SGL1, caused elongation of grains and panicle internodes. Because cell size in SG1:OX was similar to that of WT, it was suggested that SG1 represses organ elongation via repression of cell proliferation. In addition, SG1:OX was similar to BR-deficient mutants with respect to the semidwarf phenotype with dark-green and wide erect leaves. However endogeneous BR level in the SG1:OX was comparable to WT.
In this study, we investigated whether BR-response is affected in the SG1:OX plants. We performed lamina joint inclination assay and showed that lamina joints of SG1:OX were insensitive to BL compared with those of WT. In addition, induction of BR-inducible genes, such as OsBLE2, OsBLE3 and BU1, by BL was attenuated in the SG1:OX. Together with previous results, the role of SG1 is suggested to repress elongation of organs such as panicle internodes and seeds through repression of BR response.
