Abstract
Previously, we reported on isolation of rice Short grain 1 (Sg1) gene that encodes a novel protein by activation-tagging. SG1:OX rice shows semi-dwarf phenotype with erected leaves reminiscent of brassinosteroid (BR) deficient mutants, and shows BR-insensitive lamina joint phenotype. In this study, we found that SG1:OX rice showed short culm and dense panicle phenotype, in addition to short grain phenotype. Despite short organ phenotype, cellular sizes in organs of SG1:OX rice are similar to those in WT, implicating that reduction of organ size is mainly caused by reduction of cell number. In SG1:OX line, BR-content was comparable with WT, suggesting that BR signaling or response was suppressed. Spatial expression of SG1 was monitored using GUS reporter plants. GUS activity was detected in seedling roots, nodes of stem, and young panicles mainly at lower part of rachises andtheir branches. Considering on the expression pattern and OX phenotype, SG1 may repress elongation of rice panicle by suppression of cell division. To elucidate the role of SG1, we are currently making RNAi plants repressing SG1 and its homologue.
