Abscisic Acid: Emergence of a Core Signaling Network

Abstract

Key TermsBiFC: Bimolecular fluorescence complementation; a method for monitoring in vivo protein interactions by formation of a functional fluorescent protein DELLA: family of proteins that function as negative regulators of GA signaling, and are destabilized by GA infrared thermography: method for viewing infrared light emitted by objects due to their thermal condition; excessive transpiration results in "cool" leaves osmocompatible solutes: small molecules accumulated by cells to permit osmotic adjustment to a dehydrating environment without interfering with cellular function pyrabactin: a selective ABA agonist that is not an ABA analog Abstract Abscisic acid regulates numerous developmental processes and adaptive stress responses in plants. Many ABA signaling components have been identified, but their interconnections and a consensus on the structure of the ABA signaling network have eluded researchers. Recently, several advances have led to both the identification of ABA receptors and an understanding of how key regulatory phosphatase and kinase activities are controlled by ABA. A new model for ABA action has been proposed in which the soluble PYR/PYL/RCAR receptors function at the apex of a negative regulatory pathway to directly regulate PP2C phosphatases, which in turn directly regulate SnRK2 kinases. This model unifies many previously defined signaling components and highlights the importance of future work focused on defining the direct targets of SnRK2s and PP2Cs, dissecting the mechanisms of hormone interactions (i.e. cross-talk) and defining connections between additional known signaling components and this pathway, and determining how many other pathways control ABA signaling.Abscisic Acid: A brief history ABA was discovered in the 1960s. Reviews of its discovery and early chemistry and biology were published in 1969 and 1974 (2, 105). Briefly, ABA was isolated by several groups using activity-guided purification approaches to isolate endogenous growth regulators. Addicott's group at the USDA was searching for compounds isolated from cotton that promote leaf abscission, using a cotyledon abscission assay to guide purification (122). The compound isolated, originally named abscisin II, was also determined to inhibit Avena coleoptile growth (122). ABA's abscission promoting effect was subsequently determined to be partly an indirect consequence of inducing ethylene biosynthesis (26). The Wareing and Cornforth groups in the UK searched for compounds that promote bud dormancy, reasoned that such compounds would be general growth inhibitors, and ultimately isolated dormin as a wheat embryo germination inhibitor present in sycamore leaf extracts. Chemical analyses showed dormin and abscisin II to be the same compound (25), which was ultimately renamed abscisic acid. A third growth inhibitory activity originally isolated from Aegopodium tubers in the 1950s and named -inhibitor (8) was also determined to be ABA (104); thus, the widespread occurrence and importance of ABA as a plant growth regulator was esta...

Multiple exposures to drought 'train' transcriptional responses in Arabidopsis

“…This result demonstrates that the higher ABA basal levels during recovery periods are not sufficient for maintaining the transcriptional memory. Therefore, we conclude that although ABA is critically required for inducing the transcriptional responses from both non-trainable and trainable genes 15 , ABA levels do not explain the super-induction of trained genes or the maintenance of transcriptional memory in the recovery state.…”

“…The phytohormone ABA induces transcription from Arabidopsis dehydration stressresponse genes 15 and was examined as a potential factor in stress memory responses. Endogenous ABA levels repetitiously increased upon each dehydration stress, but returned to low levels during each recovery treatment (Fig.…”

Structural insights into PYR/PYL/RCAR ABA receptors and PP2Cs

“…ABA plays a pivotal role to coordinate plant response under water stress situations as well as to regulate plant growth and development [1].…”

Potencial germinativo de sementes e qualidade de keikis de Dendrobium nobile em diferentes fases do desenvolvimento dos frutos

“…Sabe-se que o ABA regula a maturação e a dormência de sementes e seu transporte é mais abundante na seiva floemática e atinge níveis máximos nas sementes durante a embriogênese (VICENTE-CARBAJOSA & CARBONERO, 2005;CUTLER et al, 2010). Em frutos colhidos aos 90 DAP, os teores de ABA provavelmente não foram suficientes para finalizar a maturação das sementes potencialmente viáveis.…”