Overexpression of ABI5 Binding Proteins Suppresses Inhibition of Germination Due to Overaccumulation of DELLA Proteins

Abstract

Abscisic acid (ABA) and gibberellic acid (GA) antagonistically regulate many aspects of plant growth, including seed dormancy and germination. The effects of these hormones are mediated by a complex network of positive and negative regulators of transcription. The DELLA family of proteins repress GA response, and can promote an ABA response via interactions with numerous regulators, including the ABA-insensitive (ABI) transcription factors. The AFP family of ABI5 binding proteins are repressors of the ABA response. This study tested the hypothesis that the AFPs also interact antagonistically with DELLA proteins. Members of these protein families interacted weakly in yeast two-hybrid and bimolecular fluorescence complementation studies. Overexpression of AFPs in sleepy1, a mutant that over-accumulates DELLA proteins, suppressed DELLA-induced overaccumulation of storage proteins, hyperdormancy and hypersensitivity to ABA, but did not alter the dwarf phenotype of the mutant. The interaction appeared to reflect additive effects of the AFPs and DELLAs, consistent with action in convergent pathways.

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

“…However, AFP OE does not modify the dwarf and poor fertility phenotype of the sly mutant, but brings about a reduction in the accumulation of the seed storage proteins associated with the sly mutation. Finkelstein and Lynch [ 13 ] propose that the reported interactions are suggestive of additive effects of AFPs and DELLAs, which is consistent with these proteins acting in convergent pathways.…”

“…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 ].…”

“…Extensive interactions between ABI5, on the one hand, and AFPs and DELLAs on the other hand, have been reported. In their work, Finkelstein and Lynch [ 13 ] explored the possibility of an interaction between DELLAs and AFP proteins. By using yeast two-hybrid and bimolecular fluorescence complementation assays, direct interactions at different levels of intensity between DELLA and AFP family members were detected.…”

“…By using yeast two-hybrid and bimolecular fluorescence complementation assays, direct interactions at different levels of intensity between DELLA and AFP family members were detected. Finkelstein and Lynch [ 13 ] also investigated potential genetic interactions between AFPs and DELLA proteins. They found that the overexpression (OE) of AFP proteins in a sleepy1 ( sly1 ) mutant background, a hyperdormant mutant where the GA response is repressed due to the overaccumulation of DELLA proteins, suppresses sly1 hyperdormancy and hypersensitivity to ABA.…”

OsNAC120 balances plant growth and drought tolerance by integrating GA and ABA signaling in rice

“…The DELLA protein has been regarded as a central connection between GA and other hormone signaling pathways ( Daviere et al., 2008 ; Golldack et al., 2013 ; Claeys et al., 2014 ; Zheng et al., 2016 ; Ito et al., 2018 ). DELLA modulates the expression of a set of downstream genes by interacting with transcription factors involved in ABA signaling ( Hu et al., 2019 ; Sun et al., 2020 ; Finkelstein and Lynch, 2022 ). Arabidopsis GAI (GIBBERELLIN INSENSITIVE) and RGA (REPRESSOR OF GA1-3) function in response to heat stress by interacting with the transcription factors ABSCISIC ACID-INSENSITIVE 3 (ABI3) and ABI5 ( Lim et al., 2013 ), and RGA-LIKE2 (RGL2) inhibits seed germination by stimulating ABA synthesis and ABI5 activity ( Piskurewicz et al., 2008 ).…”