Boron Deficiency Increases Cytosolic Ca2+ Levels Mainly via Ca2+ Influx from the Apoplast in Arabidopsis thaliana Roots.

Carlos Quiles-Pando,Jesús Rexach,M Teresa Navarro-Gochicoa,Juan J Camacho-Cristóbal,Agustín González-Fontes,M Begoña Herrera-Rodríguez

doi:10.3390/ijms20092297

Carlos Quiles-Pando, Jesús Rexach + Show 4 more

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https://doi.org/10.3390/ijms20092297

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Abstract

Boron (B) is a micronutrient for plant development, and its deficiency alters many physiological processes. However, the current knowledge on how plants are able to sense the B-starvation signal is still very limited. Recently, it has been reported that B deprivation induces an increase in cytosolic calcium concentration ([Ca2+]cyt) in Arabidopsis thaliana roots. The aim of this work was to research in Arabidopsis whether [Ca2+]cyt is restored to initial levels when B is resupplied and elucidate whether apoplastic Ca2+ is the major source for B-deficiency-induced rise in [Ca2+]cyt. The use of chemical compounds affecting Ca2+ homeostasis showed that the rise in root [Ca2+]cyt induced by B deficiency was predominantly owed to Ca2+ influx from the apoplast through plasma membrane Ca2+ channels in an IP3-independent manner. Furthermore, B resupply restored the root [Ca2+]cyt. Interestingly, expression levels of genes encoding Ca2+ transporters (ACA10, plasma membrane PIIB-type Ca2+-ATPase; and CAX3, vacuolar cation/proton exchanger) were upregulated by ethylene glycol tetraacetic acid (EGTA) and abscisic acid (ABA). The results pointed out that ACA10, and especially CAX3, would play a major role in the restoration of Ca2+ homeostasis after 24 h of B deficiency.

Highlights

Plant ability to respond appropriately to variations in soil nutrient concentrations is of essential relevance for plant survival
Very recently it has been reported that B deficiency enlarged [Ca2+]cyt in the Malus domestica pollen tube tip [31]. These findings suggest that Ca2+ is involved in a signaling pathway triggered by B deficiency, currently, precise mechanisms underlying this route remain unknown
It was described that B starvation induced overexpression of stress-responsive genes in tobacco BY-2 cells and a higher Ca2+ influx when compared to control cells [29]. These results were consistent with the increased root [Ca2+]cyt and expression of Ca2+-related genes described in Arabidopsis plants upon 6 and 24 h of B deficiency [30]

Summary

Introduction

Plant ability to respond appropriately to variations in soil nutrient concentrations is of essential relevance for plant survival. Nutrients such as nitrate, phosphate, potassium, sulfate, and iron act as signals that can be perceived by plants [1]. In vascular plants, complex signaling pathways have evolved to sense their nutrient availability and, trigger a response that allows them to adapt to a changing environment [2]. Ca2+ channels allow Ca2+ influx into the cytosol, while Ca2+ transporters are involved in Ca2+ efflux into particular reservoirs and apoplasts [3,5,6,7]. Ca2+ influx is performed by several categories of Ca2+-permeable channels, cyclic nucleotide-gated ion channels (CNGCs) being one of these types [8]

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