Salt-Sensitive Signaling Networks in the Mediation of K + /Na + Homeostasis Gene Expression in Glycyrrhiza uralensis Roots

• Published in: Frontiers in plant science 2017-08, Vol.8, p.1403-1403
• Main Authors: Lang, Tao, Deng, Shurong, Zhao, Nan, Deng, Chen, Zhang, Yinan, Zhang, Yanli, Zhang, Huilong, Sa, Gang, Yao, Jun, Wu, Caiwu, Wu, Yanhong, Deng, Qun, Lin, Shanzhi, Xia, Jianxin, Chen, Shaoliang
• Format: Article
• Language: English
• Subjects: eATP; H2O2; ion flux; liquorice; NaCl; Plant Science
• ISSN: 1664-462X; 1664-462X
• DOI: 10.3389/fpls.2017.01403

We investigated the effects of salt-sensitive signaling molecules on ionic fluxes and gene expression related to K /Na homeostasis in a perennial herb, , during short-term NaCl stress (100 mM, 24 h). Salt treatment caused more pronounced Na accumulation in root cells than in leaf cells. Na ions were mostly compartmentalized in vacuoles. Roots exposed to NaCl showed increased levels of extracellular ATP (eATP), cytosolic Ca , H O , and NO. Steady-state flux recordings revealed that these salt-sensitive signaling molecules enhanced NaCl-responsive Na efflux, due to the activated Na /H antiport system in the plasma membrane (PM). Moreover, salt-elicited K efflux, which was mediated by depolarization-activated cation channels, was reduced with the addition of Ca , H O , NO, and eATP. The salt-adaptive effects of these molecules (Na extrusion and K maintenance) were reduced by pharmacological agents, including LaCl (a PM Ca channel inhibitor), DMTU (a reactive oxygen species scavenger), cPTIO (an NO scavenger), or PPADS (an antagonist of animal PM purine P2 receptors). RT-qPCR data showed that the activation of the PM Na /H antiport system in salinized roots most likely resulted from the upregulation of two genes, and , which encoded the PM Na /H antiporter, salt overly sensitive 1 (SOS1), and H -ATPase, respectively. Clear interactions occurred between these salt-sensitive agonists to accelerate transcription of salt-responsive signaling pathway genes in roots. For example, Ca , H O , NO, and eATP promoted transcription of (salt overly sensitive 3) and/or (CBL-interacting protein kinase) to activate the predominant Ca -SOS signaling pathway in salinized liquorice roots. eATP, a novel player in the salt response of , increased the transcription of , (respiratory burst oxidase homolog protein D), (nitrate reductase), , and (the mitogen-activated protein kinases 3 and 6). Moreover, and expression levels were enhanced by H O in NaCl-stressed roots. Our results indicated that eATP triggered downstream components and interacted with Ca , H O , and NO signaling to maintain K /Na homeostasis. We propose that a multiple signaling network regulated K /Na homeostasis in NaCl-stressed roots.