Role of Ca2+ in Mediating Plant Responses to Extracellular ATP and ADP.

Greg Clark,Stanley Roux

doi:10.3390/ijms19113590

Greg Clark, Stanley Roux

Open Access

https://doi.org/10.3390/ijms19113590

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Abstract

Among the most recently discovered chemical regulators of plant growth and development are extracellular nucleotides, especially extracellular ATP (eATP) and extracellular ADP (eADP). Plant cells release ATP into their extracellular matrix under a variety of different circumstances, and this eATP can then function as an agonist that binds to a specific receptor and induces signaling changes, the earliest of which is an increase in the concentration of cytosolic calcium ([Ca2+]cyt). This initial change is then amplified into downstream-signaling changes that include increased levels of reactive oxygen species and nitric oxide, which ultimately lead to major changes in the growth rate, defense responses, and leaf stomatal apertures of plants. This review presents and discusses the evidence that links receptor activation to increased [Ca2+]cyt and, ultimately, to growth and diverse adaptive changes in plant development. It also discusses the evidence that increased [Ca2+]cyt also enhances the activity of apyrase (nucleoside triphosphate diphosphohydrolase) enzymes that function in multiple subcellular locales to hydrolyze ATP and ADP, and thus limit or terminate the effects of these potent regulators.

Highlights

The growth and development of plants are controlled by a remarkably diverse array of endogenous chemical regulators beyond the hormones typically featured in textbooks, and new discoveries add to the list of these regulatory compounds every year
Changes in [Ca2+]cyt are characteristically early steps in the signaling pathways induced by most plant growth regulators, so it is not surprising that it is one of the first signaling changes induced by extracellular ATP (eATP)
This review describes evidence that eATP-induced changes in [Ca2+]cyt both precede and are necessary for the downstream signaling changes that promote the physiological responses to eATP

Summary

Introduction

The growth and development of plants are controlled by a remarkably diverse array of endogenous chemical regulators beyond the hormones typically featured in textbooks, and new discoveries add to the list of these regulatory compounds every year. When scientists investigated whether plants had a similar response system, they tested whether the application of ATP could induce a rapid change in [Ca2+]cyt, and the positive results that were observed in cells of Arabidopsis root and shoot tissue [7,11] initiated an active search for purinergic receptors in plants. Two studies by Demidchik et al [5,6] suggest that P2K1 may not be the only eATP/eADP receptor in plants, because they found that the kinetics of the induced increase in [Ca2+]cyt differed depending on whether eATP or eADP was the extracellular nucleotide agonist.

Results

Conclusion