Extracellular ATP receptors P2Ks are involved in regulating systemic calcium of Arabidopsis in response to local NaCl stress

Abstract

Extracellular ATP (eATP) and its receptors play important roles in the regulation of the responses of plants to environmental stimulation. In the present work, application of NaCl to the roots of Arabidopsis (Arabidopsis thaliana) seedlings triggered an increase of Ca²⁺ level not only in the stressed root but also in the systemic organs distant from the root, including the hypocotyl and cotyledon, and the eATP level also was increased in the stressed root and those systemic organs under such local salt stress. Application of exogenous ATP to the root also evoked local and systemic increase of Ca²⁺ level in the seedlings. The lectin receptors kinase I.9 (P2K1) and I.5 (P2K2) are known as the receptors of eATP in Arabidopsis. By comparison of wild-type and P2Ks mutant plants (including p2k1 single-mutant, p2k2 single-mutant, and p2k1p2k2 double-mutant plants), it was found that the local and systemic increases of Ca²⁺ level in the response to local salt stress were weakened by the mutation of P2Ks. In addition, the mutation of P2K1 and P2K2 also attenuates the systemic resistance of cotyledon to salt stress, which was induced by the application of NaCl to the root. These results indicate that the local and systemic Ca²⁺ response to local salt stress is associated with eATP/P2Ks signaling in the plant.