Plant hormone-mediated regulation of stress responses

Abstract

BackgroundBeing sessile organisms, plants are often exposed to a wide array of abiotic and biotic stresses. Abiotic stress conditions include drought, heat, cold and salinity, whereas biotic stress arises mainly from bacteria, fungi, viruses, nematodes and insects. To adapt to such adverse situations, plants have evolved well-developed mechanisms that help to perceive the stress signal and enable optimal growth response. Phytohormones play critical roles in helping the plants to adapt to adverse environmental conditions. The elaborate hormone signaling networks and their ability to crosstalk make them ideal candidates for mediating defense responses.ResultsRecent research findings have helped to clarify the elaborate signaling networks and the sophisticated crosstalk occurring among the different hormone signaling pathways. In this review, we summarize the roles of the major plant hormones in regulating abiotic and biotic stress responses with special focus on the significance of crosstalk between different hormones in generating a sophisticated and efficient stress response. We divided the discussion into the roles of ABA, salicylic acid, jasmonates and ethylene separately at the start of the review. Subsequently, we have discussed the crosstalk among them, followed by crosstalk with growth promoting hormones (gibberellins, auxins and cytokinins). These have been illustrated with examples drawn from selected abiotic and biotic stress responses. The discussion on seed dormancy and germination serves to illustrate the fine balance that can be enforced by the two key hormones ABA and GA in regulating plant responses to environmental signals.ConclusionsThe intricate web of crosstalk among the often redundant multitudes of signaling intermediates is just beginning to be understood. Future research employing genome-scale systems biology approaches to solve problems of such magnitude will undoubtedly lead to a better understanding of plant development. Therefore, discovering additional crosstalk mechanisms among various hormones in coordinating growth under stress will be an important theme in the field of abiotic stress research. Such efforts will help to reveal important points of genetic control that can be useful to engineer stress tolerant crops.

Exogenous putrescine increases the responsiveness of thermodormant Avena fatua L. caryopses to karrikinolide and gibberellic acid

“…ABA plays a major role in inducing and maintaining seed dormancy (Kermode 2005) and there is also vast evidence of its involvement in plant responses to environmental stresses, especially caused by abiotic factors (Verma et al 2016). There are several reports proving the connection between ABA signaling, polyamines metabolism and plant defense system (Toumi et al 2010;Marco et al 2011;Saha et al 2015).…”

Phytohormones: the chemical language in Magnaporthe oryzae-rice pathosystem

“…Particularly, SA mediates plant resistance towards biotrophic or semibiotrophic pathogens, and is involved in the systemic acquired resistance (SAR) in which a pathogenic attack on one part of the plant induces resistance in other parts; JAs and ET mediate resistance to necrotropic plant pathogens (Broekaert et al 2006; Pieterse et al 2012). Auxins, CKs, BRs, ABA and GA are mainly involved in regulating various aspects of plant growth and development, including root and shoot growth, flowering, leaf senescence, fruit ripening, seeds dormancy and germination, etc, but they may also participate in disease resistance through SA, JAs or ET signaling regulation (Jiang et al 2013; Verma et al 2016; Nolan et al 2017). …”

In-depth analysis of jasmonate-mediated indole-3-acetic acid (IAA) biosynthesis and its implication in plant development

“…On the other hand, we found that rather YUC9 than YUC8 has a possible role in plant response to water deficit by conferring tolerance to drought. Among the known plant hormones, abscisic acid (ABA), salicylic acid (SA), jasmonic acid (JA) and ethylene (ET) are known to play important roles in mediating responses to multiple biotic and abiotic stresse (Forcat et al 2008;Verma et al 2016). Here, we demonstrated the implication of YUC8 and YUC9 in the response to spider mite attack and drought stress responses (See Sections 4.2.1 and 4.2.3).…”

“…In this context, the perception of environmental stimuli alters the concentration of several signaling molecules, including plant hormones, intracellular Ca 2+ levels, and secondary compounds such as, e.g., inositol phosphate, sugars or reactive oxygen species (Pozo et al 2015;Verma et al 2016). Among these, the phytohormones are considered the most important plant substances for regulating physiological and molecular responses.…”