Populus euphratica JRL Mediates ABA Response, Ionic and ROS Homeostasis in Arabidopsis under Salt Stress.

Shaoliang Chen,Yan-Li Zhang,Nan Zhao,Gang Sa,Huilong Zhang,Cunfu Lu,Chen Deng,Yi-Nan Zhang,Xiaoyang Zhou,Rui Zhao,Shurong Deng,Jun Yao,Shanzhi Lin

doi:10.3390/ijms20040815

Abstract

Sodium chloride (NaCl) induced expression of a jacalin-related mannose-binding lectin (JRL) gene in leaves, roots, and callus cultures of Populus euphratica (salt-resistant poplar). To explore the mechanism of the PeJRL in salinity tolerance, the full length of PeJRL was cloned from P. euphratica and was transformed into Arabidopsis. PeJRL was localized to the cytoplasm in mesophyll cells. Overexpression of PeJRL in Arabidopsis significantly improved the salt tolerance of transgenic plants, in terms of seed germination, root growth, and electrolyte leakage during seedling establishment. Under NaCl stress, transgenic plants retained K+ and limited the accumulation of Na+. PeJRL-transgenic lines increased Na+ extrusion, which was associated with the upward regulation of SOS1, AHA1, and AHA2 genes encoding plasma membrane Na+/proton (H+) antiporter and H+-pumps. The activated H+-ATPases in PeJRL-overexpressed plants restricted the channel-mediated loss of K+ that was activated by NaCl-induced depolarization. Under salt stress, PeJRL–transgenic Arabidopsis maintained reactive oxygen species (ROS) homeostasis by activating the antioxidant enzymes and reducing the production of O2− through downregulation of NADPH oxidases. Of note, the PeJRL-transgenic Arabidopsis repressed abscisic acid (ABA) biosynthesis, thus reducing the ABA-elicited ROS production and the oxidative damage during the period of salt stress. A schematic model was proposed to show the mediation of PeJRL on ABA response, and ionic and ROS homeostasis under NaCl stress.

Highlights

Plants are frequently challenged by various environmental stressors, which inhibit plant growth and crop production
Jacalin-related lectin (JRL) genes such as TaJRL2.1, TaJRL53, TaJRL18.2, TaJRL27, TaJRL43, and TaJRL48 are induced in inflorescence after Fusarium graminearum inoculation, and TaJRL55 is induced by Hessian fly infection [16]
Exposure to NaCl (125–200 mM) significantly increased PeJRL transcript levels relative to the reference gene in P. euphratica, the pattern varied between callus, leaves, and roots (Figure 1)

Summary

Introduction

Plants are frequently challenged by various environmental stressors, which inhibit plant growth and crop production. Salt stress leads to water deficiency and ion toxicity, which cause oxidative damage in plants [5,6]. High salt alters the expression level of stress-related genes that are involved in ionic homeostasis and anti-oxidant defense [7]. It has been shown that plant lectins inhibit infection of pathogen fungi and insects [13,14,15]. Digital expression analysis (DEA) has shown that 25 TaJRL genes were responsive to abiotic stress, such as water shortage, low temperature, aluminium, and salt stress [16]. A rice (Oryza sativa L.) lectin was isolated from salt-stressed plants and previously characterized by Zhang et al (2000) [19]. The regulatory roles of Populus JRL family genes in salt tolerance are not yet fully understood in trees

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Conclusion