Department of Plant Science, Plant Genomics and Breeding Institute, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Korea.
Department of Plant Molecular Systems Biotechnology, Crop Biotech Institute, Kyung Hee University, Yongin 17104, Korea.
Int J Mol Sci. 2020 Mar 18;21(6):2090. doi: 10.3390/ijms21062090.
Changes in plant architecture, such as leaf size, leaf shape, leaf angle, plant height, and floral organs, have been major factors in improving the yield of cereal crops. Moreover, changes in grain size and weight can also increase yield. Therefore, screens for additional factors affecting plant architecture and grain morphology may enable additional improvements in yield. Among the basic Helix-Loop-Helix (bHLH) transcription factors in rice (), we found an enhancer-trap T-DNA insertion mutant of (termed ). The mutant showed a wide leaf angle phenotype and produced long grains, similar to the phenotypes of mutants with increased brassinosteroid (BR) levels or enhanced BR signaling. Reverse transcription-quantitative PCR analysis showed that BR signaling-associated genes are largely upregulated in , but BR biosynthesis-associated genes are not upregulated, compared with its parental cultivar 'Dongjin'. Consistent with this, was hypersensitive to BR treatment. Scanning electron microscopy revealed that the expansion of cell size in the adaxial side of the lamina joint was responsible for the increase in leaf angle in . The expression of cell-elongation-associated genes encoding expansins and xyloglucan endotransglycosylases/hydrolases increased in the lamina joints of leaves in . The regulatory function of OsbHLH079 was further confirmed by analyzing overexpression and gene silencing lines. The plants showed similar phenotypes to , and the plants displayed opposite phenotypes to . Taking these observations together, we propose that functions as a positive regulator of BR signaling in rice.
植物结构的变化，如叶片大小、形状、角度、株高和花器官，一直是提高谷类作物产量的主要因素。此外，粒重和粒型的改变也可以增加产量。因此，筛选影响植物结构和谷物形态的其他因素可能会进一步提高产量。在水稻中的基本螺旋-环-螺旋(bHLH)转录因子中，我们发现了一个增强子捕获 T-DNA 插入突变体 ()，称为 。该突变体表现出宽叶角表型，并产生长粒，类似于油菜素内酯(BR)水平升高或 BR 信号增强的突变体的表型。反转录定量 PCR 分析表明，与亲本品种“Dongjin”相比，BR 信号相关基因在 中大量上调，但 BR 生物合成相关基因没有上调。与此一致， 对 BR 处理敏感。扫描电子显微镜显示，叶关节腹侧细胞大小的扩张是导致 叶角增加的原因。在 叶片的叶关节中，编码扩展蛋白和木葡聚糖内转糖基酶/水解酶的细胞伸长相关基因的表达增加。通过分析 过表达和 基因沉默系进一步证实了 OsbHLH079 的调节功能。 植株表现出与 相似的表型， 植株表现出与 相反的表型。综上所述，我们提出 作为水稻 BR 信号的正调控因子发挥作用。
