Role Of Abscisic Acid In Regulation Research Articles

Abscisic acid signaling and crosstalk with phytohormones in regulation of environmental stress responses

Frequently changing environmental conditions pose unwarranted threat to plants life and impose serious penalties in terms of arrested growth, metabolism and ultimately the yield. Being rooted, plants cannot avoid the stresses but equipped well to survive and produce. Among the stress modulatory responses, an isoprenoid phytohormone abscisic acid (ABA) proved its significance by regulating the growth, development and stress responses as a signaling mediator. Abscisic acid also controls various physiological, biochemical and molecular processes in plants under non-stress conditions. It regulates seed dormancy, stomatal closure, leaf abscission, senescence, fruit ripening, legume-Rhizobium symbiosis and a number of stress related functions. In stressful conditions, ABA perception and signaling controls downstream responses at transcriptional and posttranscriptional level. The present review discusses ABA homeostasis, its perception and signaling along with physiological and molecular responses of ABA under critical conditions including drought, heavy metal, salinity, and temperature stress is specified. The recent molecular diagnostics reported through high throughput technologies reveal the role of ABA in regulation of different physiological mechanisms through integration of environmental cues via its positive and negative crosstalks with other phytohormones (like auxin, gibberellin, cytokinin, ethylene, salicylic acid, brassinosteroids, jasmonic acid, strigolactones, and melatonin) and potent chemical messengers like polyamines, sugars, NO and H2S mediated by several receptors, transporters, bZIP TFs and regulatory proteins has also been focused in detail. The data supporting the findings of this study are available from the corresponding author, (Author name), upon request.

Importance of ABA homeostasis under terminal drought stress in regulating grain filling events

Recent studies suggest that abscisic acid (ABA) at its basal level plays an important role during seed set and grain filling events. Under drought stress ABA levels were found to be significantly enhanced in the developing seed. Until now we lack an understanding of (A) ABA homeostasis in developing seeds under terminal drought and (B) the interactive role of ABA in regulating the starch biosynthesis pathway in developing grains under terminal drought. We have recently reported the possible regulation of ABA homeostasis in source (flag leaf) and sink (developing grains) tissues under post-anthesis drought stress in barley and concluded that significantly enhanced ABA levels in developing grains are due to strong activation of the ABA deconjugation pathway and fine regulation of the ABA biosynthesis-degradation pathway.1 Additionally, we provided evidence for the role of ABA in differential regulation of starch biosynthesis genes and a significant upregulation of starch degradation beta amylase genes under drought, i.e. ABA not only influences the rate of starch accumulation but also starch quality.

Levels of endogenous abscisic acid in achenes of Rosa rugosa during dormancy release and germination

Germination experiments on isolated embryos and intact achenes from Rosa rugosa L. var. rubra revealed the existence of both coat‐induced and embryo dormancy. Studies were made on the quantitative changes in abscisic acid (ABA) of achenes during both a stratification period at 4°C and a subsequent germination period at 20°C. Controls were run in parallel at 17°C. Dormant, unimbibed achenes contained large amounts of ABA. The level fell rapidly during the early stages of stratification at 4°C, mainly due to leakage, and then the decline levelled off. The reduction of ABA content during germination was less and followed a tri‐phasic pattern. Under the control conditions, the ABA level also fell although still faster, the amounts present being consistently below those detected in the corresponding cold‐stratified samples. The content of alkali‐hydrolysable ABA was low and not affected either by the duration or by the temperature of stratification. The investigation shows that termination of dormancy is not simply a consequence of a fall in the content of endogenous ABA and supports the current debate questioning the central role of ABA in regulation of dormancy breakage and of germination.