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

Abstract

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 Arabidopsis. 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 (AGB1) mutants, agb1-2 and N692967, 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 MYB62 in two backgrounds including the wild-type (MYB62/WT Col-0) and agb1 mutants (MYB62/agb1) in Arabidopsis. Genetic analysis showed that under GA3 treatment, the height of the transgenic plants MYB62/WT and MYB62/agb1 was lower than that of WT. The height of MYB62/agb1 plants was closer to MYB62/WT plants and higher than that of mutants agb1-2 and N692967, suggesting that MYB62 is downstream of AGB1 in the GA pathway. qRT-PCR and competitive DNA binding assays indicated that MYB62 can bind MYB elements in the promoter of GA2ox7, a GA degradation gene, to activate GA2ox7 transcription. AGB1 affected binding of MYB62 on the promoter of GA2ox7, thereby negatively regulating th eactivity of MYB62.

Advances in the Molecular Mechanisms of Abscisic Acid and Gibberellins Functions in Plants 2.0

“…These works cover outstanding advances in the molecular mechanisms by which GA and ABA control different aspects of plant physiology, development and for ABA, also in the response to abiotic stresses. In line with this, the original research articles investigate the effects of ABA on epicuticular wax metabolism regulation in a citrus fruit cultivar [ 9 ], the regulation of WNK kinases and their comprehensive interaction with ABA components [ 10 ], CCD family members in poplar and their expression patterns in response to ABA and abiotic stress [ 11 ], the molecular function of NAC transcription factor PwNAC11 in drought stress [ 12 ], the interaction between AFPs and DELLA proteins [ 13 ], and the molecular mechanism by which AGB1 regulates the GA pathway in Arabidopsis [ 14 ]. The reviews published in this Special Issue focus on how ABA regulates plant development and stress tolerance through alternative splicing [ 15 ], the mechanisms of ABA-mediated drought stress responses in plants [ 16 ], the roles of ABA and GA in stem/root tuber development [ 17 ] and the molecular mechanisms underlying ABA and GA regulation of seed development from embryogenesis to maturation [ 18 ].…”

“…Unlike the above-discussed research manuscripts, which deal with different aspects of ABA, or the ABA and GA function, in plants, the work of Qi et al [ 14 ] focused on GA, and specifically on two components of the GA pathway: Arabidopsis G-protein β subunit (AGB1) and the DNA-binding protein MYB62, a GA pathway suppressor. Heterotrimeric G proteins are transmembrane proteins that transduce signals from a wide range of extracellular stimuli and regulate several cellular and physiological functions in eukaryotes.…”

“…In plants, G proteins are involved in developmental processes, stress responses and innate immunity [ 22 ]. Qi et al [ 14 ] identified mutants agb1-2 and N692967 that are affected in AGB1, which are dwarfs and contain significantly reduced GA levels compared to the wild type when undergoing GA 3 treatment. By using yeast-two hybrid, pull-down and firefly luciferase complementary imaging, Qi et al [ 14 ] found that AGB1 physically interacts with the DNA-binding region of GA pathway suppressor MYB62.…”

“…Qi et al [ 14 ] identified mutants agb1-2 and N692967 that are affected in AGB1, which are dwarfs and contain significantly reduced GA levels compared to the wild type when undergoing GA 3 treatment. By using yeast-two hybrid, pull-down and firefly luciferase complementary imaging, Qi et al [ 14 ] found that AGB1 physically interacts with the DNA-binding region of GA pathway suppressor MYB62. The results of the genetic analysis carried out by Qi et al [ 14 ] are consistent with MYB62 acting downstream of AGB1 in the GA pathway.…”

“…By using yeast-two hybrid, pull-down and firefly luciferase complementary imaging, Qi et al [ 14 ] found that AGB1 physically interacts with the DNA-binding region of GA pathway suppressor MYB62. The results of the genetic analysis carried out by Qi et al [ 14 ] are consistent with MYB62 acting downstream of AGB1 in the GA pathway. The expression analysis performed by RT-qPCR and competitive DNA binding assays revealed that MYB62 can bind MYB elements in the promoter of downstream gene GA2ox7 (encoding a GA degradation enzyme) to induce GA2ox7 transcription.…”