Overexpression of GmGAMYB Accelerates the Transition to Flowering and Increases Plant Height in Soybean

Abstract

The flowering time and plant height of soybean are important agronomic characters, which control the adaptability and yield of soybean. R2R3 MYB transcription factor plays an important regulatory role in plant growth and development. In this study, soybean <i>GmGAMYB</i> gene of R2R3-MYB type was induced by long-days (LDs). <i>GmGAMYB</i> showed higher transcriptional levels in the flowers, leaves and pods of soybean. Overexpression of <i>GmGAMYB</i> in transgenic soybean showed earlier flowering time and maturity in LDs and short-days (SDs). <i>GmGAMYB</i> interacted with <i>GmGBP1</i> and might promote flowering time by up-regulating the expression of <i>GmFULc</i> gene in soybean. Moreover, the expression level of <i>GmGAMYB</i> was also induced by gibberellins (GAs) and the plant height of <i>GmGAMYB-ox</i> plants was significantly increased, which was caused by the enlargement of internode cell in stem. Furthermore, <i>GmGAMYB</i> overexpression led to increased GA sensitivity in the hypocotyl of soybean seedlings compared with WT. <i>GmGAMYB</i> may be a positive regulator of GA response of promoting plant height by up-regulating the expression of <i>GmGA20ox</i> gene in soybean. Together, our studies preliminarily showed that the partial functions of <i>GmGAMYB</i> in regulating flowering time and GA pathway.