Objective Zoysia japonica is a warm season lawn grass, which has many excellent characters and is widely used. One of the limiting factors for Z. japonica is its early leaf de-greening in late autumn and early winter in the north. The objective of this study was to investigate the underlying mechanism of leaf de-greening process of Z. japonica in response to low temperature stress.
Method In this experiment, Z. japonica was exposed to light for 14 h (4 ℃) and dark for 10 h (2 ℃) in a growth chamber to simulate cold stress. Chlorophyll content, the activities of key enzymes in chlorophyll synthesis and degradation pathway and the expression of genes related to chlorophyll metabolism were studied.
Result Z. japonica leaves turned yellow and curly under low temperature stressed conditions. The concentrations of chlorophyll, chlorophyll a, chlorophyll b , the ratio of chlorophyll a to chlorophyll b , the activities of ALAD, PBGD and the content of PBG in low temperature treatment group were significantly lower than CK. The activity of MDCase increased significantly. Chlorophyll synthesis related genes (except ZjMgCH2) were down-expressed and chlorophyll degradation related genes (except ZjNYC1) were high-expressed.
Conclusion Chlorophyll synthesis decreases and chlorophyll degradation increases in Z. japonica under low temperature stress. In addition, MDCase is proved to be the key factor in the chlorophyll degradation pathway of Z. japonica. This study provides a theoretical basis for understanding mechanisms underlying the stay-green characters of Z. japonica. At the same time, it has great significance to breeding variety of Z. japonica with stay-green character.