Plant Hormone Signaling Crosstalks between Biotic and Abiotic Stress Responses.

Yee-Shan Ku,Ming-Yan Cheung,Hon-Ming Lam,Mariz Sintaha

doi:10.3390/ijms19103206

Yee-Shan Ku, Ming-Yan Cheung + Show 2 more

Open Access

https://doi.org/10.3390/ijms19103206

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Abstract

In the natural environment, plants are often bombarded by a combination of abiotic (such as drought, salt, heat or cold) and biotic (necrotrophic and biotrophic pathogens) stresses simultaneously. It is critical to understand how the various response pathways to these stresses interact with one another within the plants, and where the points of crosstalk occur which switch the responses from one pathway to another. Calcium sensors are often regarded as the first line of response to external stimuli to trigger downstream signaling. Abscisic acid (ABA) is a major phytohormone regulating stress responses, and it interacts with the jasmonic acid (JA) and salicylic acid (SA) signaling pathways to channel resources into mitigating the effects of abiotic stresses versus defending against pathogens. The signal transduction in these pathways are often carried out via GTP-binding proteins (G-proteins) which comprise of a large group of proteins that are varied in structures and functions. Deciphering the combined actions of these different signaling pathways in plants would greatly enhance the ability of breeders to develop food crops that can thrive in deteriorating environmental conditions under climate change, and that can maintain or even increase crop yield.

Highlights

The individual effects of isolated abiotic and biotic stresses on plants and their physiological responses to each of them have been studied extensively under experimental conditions, along with the corresponding regulatory mechanisms at the genetic and molecular levels [1,2,3,4]
NOG1-2 acts as a point of crosstalk between the abscisic acid (ABA) and jasmonic acid (JA) signaling pathways, since NOG1-2 is responsible for inducing stomatal closure as part of the ABA-dependent pathway during abiotic stress, while it causes the closing of stomata through the JA-Ileu-mediated pathway during pathogen infection [48]
Ca2+ sensors are responsible for decoding the natures of the stimuli, and the signals are transduced through the appropriate stress hormone pathways to bring forth a series of physiological responses

Summary

Introduction

The individual effects of isolated abiotic and biotic stresses on plants and their physiological responses to each of them have been studied extensively under experimental conditions, along with the corresponding regulatory mechanisms at the genetic and molecular levels [1,2,3,4]. For CMLs, in tomato, the expression of ShCML44 could be induced by cold, drought, mannitol, (osmotic stress), salt, ABA, methyl-jasmonate (MeJA), and ethephon (a plant growth regulator) [18]. The mutation of CBL10 in Arabidopsis thaliana led to a reduced tolerance of salt stress [27]. The binding of Ca2+ leads to the autophosphorylation of the protein and enhances its affinity to CaM, resulting in the activation of kinase activity [39] Several transcription factors, such as CYCLOPS and ZmNAC84, were reported to be the targets of CCaMKs [40,41,42]. The overexpression of GsCBRLK in Arabidopsis thaliana led to improved tolerance of NaCl stress and reduced sensitivity to ABA [29]. The overexpression of TaCCaMK in Arabidopsis led to decreased sensitivity to ABA and improved tolerance of NaCl during seed germination, but increased sensitivity to NaCl, with heavier chlorosis in seedlings [43]

Calcium Sensors Involved in both Abiotic and Biotic Stresses

ABA-Mediated Stress Responses

Unconventional G-proteins

Obg Superfamily

Small G-proteins

Conclusions