<i>Arabidopsis</i> G-Protein β Subunit AGB1 Negatively Regulates DNA Binding of MYB62, a Suppressor in the Gibberellin Pathway

• Main Authors: Xin Qi, Wensi Tang, Weiwei Li, Zhang He, Weiya Xu, Zhijin Fan, Yongbin Zhou, Chunxiao Wang, Zhaoshi Xu, Jun Chen, Shiqin Gao, Youzhi Ma, Ming Chen
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: International Journal of Molecular Sciences
• Subjects: <i>Arabidopsis</i>; GA signaling; <i>AGB1</i>; <i>MYB62</i>; protein interaction
• Online Access: https://www.mdpi.com/1422-0067/22/15/8270

Plant G proteins are versatile components of transmembrane signaling transduction pathways. The deficient mutant of heterotrimeric G protein leads to defects in plant growth and development, suggesting that it regulates the GA pathway in <i>Arabidopsis</i>. However, the molecular mechanism of G protein regulation of the GA pathway is not understood in plants. In this study, two G protein β subunit (<i>AGB1</i>) mutants, <i>agb1-2</i> and <i>N692967</i>, were dwarfed after exogenous application of GA₃. AGB1 interacts with the DNA-binding domain MYB62, a GA pathway suppressor. Transgenic plants were obtained through overexpression of <i>MYB62</i> in two backgrounds including the wild-type (<i>MYB62/WT</i> <i>Col-0</i>) and <i>agb1</i> mutants (<i>MYB62/agb1</i>) in <i>Arabidopsis</i>. Genetic analysis showed that under GA₃ treatment, the height of the transgenic plants <i>MYB62/WT</i> and <i>MYB62/agb1</i> was lower than that of WT. The height of <i>MYB62/agb1</i> plants was closer to <i>MYB62/WT</i> plants and higher than that of mutants <i>agb1-2</i> and <i>N692967</i>, suggesting that <i>MYB62</i> is downstream of <i>AGB1</i> in the GA pathway. qRT-PCR and competitive DNA binding assays indicated that MYB62 can bind MYB elements in the promoter of <i>GA2ox7</i>, a GA degradation gene, to activate <i>GA2ox7</i> transcription. AGB1 affected binding of MYB62 on the promoter of <i>GA2ox7</i>, thereby negatively regulating th eactivity of MYB62.