Transcriptome Analysis Revealed a Positive Role of Ethephon on Chlorophyll Metabolism of <i>Zoysia japonica</i> under Cold Stress
2022
Jiahang Zhang | Zhiwei Zhang | Wen Liu | Lijing Li | Liebao Han | Lixin Xu | Yuhong Zhao
<i>Zoysia japonica</i> is a warm-season turfgrass with a good tolerance and minimal maintenance requirements. However, its use in Northern China is limited due to massive chlorophyll loss in early fall, which is the main factor affecting its distribution and utilization. Although ethephon treatment at specific concentrations has reportedly improved stress tolerance and extended the green period in turfgrass, the potential mechanisms underlying this effect are not clear. In this study, we evaluated and analyzed chlorophyll changes in the physiology and transcriptome of <i>Z. japonica</i> plants in response to cold stress (4 °C) with and without ethephon pretreatment. Based on the transcriptome and chlorophyll content analysis, ethephon pretreatment increased the leaf chlorophyll content under cold stress by affecting two processes: the stimulation of chlorophyll synthesis by upregulating <i>ZjMgCH2</i> and <i>ZjMgCH3</i> expression; and the suppression of chlorophyll degradation by downregulating <i>ZjPAO</i>, <i>ZjRCCR</i>, and <i>ZjSGR</i> expression. Furthermore, ethephon pretreatment increased the ratio of chlorophyll a to chlorophyll b in the leaves under cold stress, most likely by suppressing the conversion of chlorophyll a to chlorophyll b due to decreased chlorophyll b synthesis via downregulation of <i>ZjCAO</i>. Additionally, the inhibition of chlorophyll b synthesis may result in energy redistribution between photosystem II and photosystem I.
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