Gibberellins and abscisic acid signal crosstalk: living and developing under unfavorable conditions

Abstract

Plants adapt to adverse environments by integrating growth and development to environmentally activated cues. Within the adaptive signaling networks, plant hormones tightly control convergent developmental and stress adaptive processes and coordinate cellular responses to external and internal conditions. Recent studies have uncovered novel antagonizing roles of the plant hormones gibberellin (GA) and abscisic acid (ABA) in integrating growth and development in plants with environmental signaling. According to current concepts, GRAS transcription factors of the DELLA and SCARECROW-LIKE (SCL) types have a key role as major growth regulators and have pivotal functions in modulating GA signaling. Significantly, current models emphasize a function of DELLA proteins as central regulators in GA homeostasis. DELLA proteins interact with the cellular GA receptor GID1 (GA-INSENSITIVE DWARF1) and degradation of DELLAs activates the function of GA. Supplementary to the prevailing view of a pivotal role of GRAS family transcriptional factors in plant growth regulation, recent work has suggested that the DELLA and SCL proteins integrate generic GA responses into ABA-controlled abiotic stress tolerance. Here, we review and discuss how GRAS type proteins influence plant development and versatile adaptation as hubs in GA and ABA triggered signaling pathways.

The Mitochondrial Protein Import Component, TRANSLOCASE OF THE INNER MEMBRANE17-1, Plays a Role in Defining the Timing of Germination in Arabidopsis

“…The maintenance of dormancy and the initiation of germination is a balance of these antagonistic hormones, with ABA levels maintaining dormancy and GA levels prompting the release of dormancy, triggering the downstream molecular events associated with germination initiation (Bewley, 1997;Holdsworth et al, 2008). Research in this area indicates a complicated regulatory network where light and cold can act as environmental cues during imbibition, increasing the amount of GA binding to the GA receptor, GIBBERELLIN-INSENSITIVE DWARF1, that subsequently binds to the DELLA repressor protein (Golldack et al, 2013). Binding of GA with the DELLA repressor results in its targeting for degradation by the ubiquitin-proteosome system, lifting the repression of transcription of a variety of genes that promotes germination (Golldack et al, 2013).…”

“…Research in this area indicates a complicated regulatory network where light and cold can act as environmental cues during imbibition, increasing the amount of GA binding to the GA receptor, GIBBERELLIN-INSENSITIVE DWARF1, that subsequently binds to the DELLA repressor protein (Golldack et al, 2013). Binding of GA with the DELLA repressor results in its targeting for degradation by the ubiquitin-proteosome system, lifting the repression of transcription of a variety of genes that promotes germination (Golldack et al, 2013).…”

Involvement of aerial organs on the ABA accumulation in roots of Citrus plants under water deficit

“…Phytohormones also play a key role in triggering responses to a wide range of adverse environmental conditions which is essential to improve or achieve stress tolerance (Kurepin et al, 2015). In this sense, modifications in phytohormones concentration is one of the first changes that takes place under stress conditions which may lead to stress avoidance or acclimation (Peleg and Blumwald, 2011;Golldack et al, 2013). However, the exact role of phytohormones under each stressful condition needs to be considered in the context of a tissue or even at the cellular level (Piotrowska and Bajguz, 2011).…”

Fundamental and applied research in ABA signaling: Regulation by ABA of the chromatin remodeling ATPase BRAHMA and biotechnological use of the PP2CA promoter.

“…GAs promotes proteasome-mediated degradation of the DELLA protein RGL2, that acts as a germination repressor (Golldack et al, 2013). On the other hand, ABA blocks germination by inducing the expression of seed specific transcription factors, such as members of B3-domain (ABI3), AP2 domain (ABI4) and bZIP domain (ABI5) families (Finkelstein, 2013).…”

“…ABA plays major roles in abiotic and biotic stress responses. It is implicated in guard cell regulation triggering stomatal closure to maintain water balance (Sirichandra et al, 2009, Merilo et al, 2015, Munemasa et al, 2015, antagonizes gibberellins (GAs) effects to fine tune growth in adverse situations (Golldack et al, 2013), controls gene expression to help with plant adaptation to stress (Bechtold et al, 2016) and also has a role in the promotion of plant resistance to pathogens restricting its entrance via stomata (McLachlan et al, 2014). Despite of the well known functions in abiotic and biotic stress, ABA is also important for the regulation of several physiological and developmental events as embryo maturation, promotion of seed desiccation tolerance and dormancy, germination and seedling establishment, primary and lateral root growth and transition from vegetative to reproductive stage (Finkelstein et al, 2002, Cutler et al, 2010, Finkelstein, 2013, Harris, 2015.…”