Melatonin Is Involved in Regulation of Bermudagrass Growth and Development and Response to Low K+ Stress

Liang Chen; Jibiao Fan; Zhengrong Hu; Xuebing Huang; Erick Amombo; Ao Liu; Aoyue Bi; Ke Chen; Yan Xie; Jinmin Fu

doi:10.3389/fpls.2017.02038

Melatonin Is Involved in Regulation of Bermudagrass Growth and Development and Response to Low K⁺ Stress

Front Plant Sci. 2017 Nov 28:8:2038. doi: 10.3389/fpls.2017.02038. eCollection 2017.

Authors

Liang Chen¹, Jibiao Fan², Zhengrong Hu^{1

3}, Xuebing Huang^{1

3}, Erick Amombo^{1

3}, Ao Liu^{1

3}, Aoyue Bi^{1

3}, Ke Chen⁴, Yan Xie¹, Jinmin Fu¹

Affiliations

¹ Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China.
² College of Animal Science and Technology, Yangzhou University, Yangzhou, China.
³ University of Chinese Academy of Sciences, Beijing, China.
⁴ College of Resources and Environmental Science, South-Central University for Nationalities, Wuhan, China.

Abstract

Melatonin (N-acetyl-5-methoxytryptamine) plays critical roles in plant growth and development and during the response to multiple abiotic stresses. However, the roles of melatonin in plant response to K⁺ deficiency remain largely unknown. In the present study, we observed that the endogenous melatonin contents in bermudagrass were remarkably increased by low K⁺ (LK) treatment, suggesting that melatonin was involved in bermudagrass response to LK stress. Further phenotype analysis revealed that exogenous melatonin application conferred Bermudagrass enhanced tolerance to LK stress. Interestingly, exogenous melatonin application also promoted bermudagrass growth and development at normal condition. Furthermore, the K⁺ contents measurement revealed that melatonin-treated plants accumulated more K⁺ in both shoot (under both control and LK condition) and root tissues (under LK condition) compared with those of melatonin non-treated plants. Expression analysis indicated that the transcripts of K⁺ transport genes were significantly induced by exogenous melatonin treatment in bermudagrass under both control and LK stress conditions, especially under a combined treatment of LK stress and melatonin, which may increase accumulation of K⁺ content profoundly under LK stress and thereby contributed to the LK-tolerant phenotype. In addition, we investigated the role of melatonin in the regulation of photosystem II (PSII) activities under LK stress. The chlorophyll fluorescence transient (OJIP) curves were obviously higher in plants grown in LK with melatonin (LK+Mel) than those of plants grown in LK medium without melatonin application for 1 or 2 weeks, suggesting that melatonin plays important roles in PSII against LK stress. After a combined treatment of LK stress and melatonin, the values for performance indexes (PI_ABS, PI_Total, and PI_CS)_, flux ratios (φP₀, ΨE₀, and φE₀) and specific energy fluxes (ET_O/RC) were significantly improved compared with those of LK stress alone, suggesting that melatonin plays positive roles in protecting PSII activity under LK stress. Collectively, this study reveals an important role of melatonin in regulating bermudagrass response to LK stress.

Keywords: K+ content; LK stress; bermudagrass; melatonin; photosystem II (PSII) activity.