Bamboo shoot-lignification delay by melatonin during low temperature storage

Bamboo shoots may become lignified after harvest and even deteriorate rapidly under low-temperature storage. Melatonin reportedly delays plant senescence. This study was designed to investigate the effect of melatonin on texture quality index, lignin formation, scavenging-enzyme activity, and transcription-factor expression in Moso bamboo (Phyllostachys edulis) shoots stored at 4 degrees C for 12 d. Application of melatonin effectively retarded shoot lignification, as indicated by a reduction in the rate of hardening and yellowing, as well as reduced lignin and cellulose contents. Furthermore, melatonin treatment inhibited phenylalanine ammonia-lyase and peroxidase activities significantly, while enhancing superoxide dismutase, catalase, and ascorbate peroxidase activities at different storage stages. Additionally, transcription factors of SND2, KNAT7, MYB20 and MYB85 from the NAC and MYB families were upregulated during postharvest storage of bamboo shoots, and melatonin treatment significantly inhibited their expression. These results suggest that the delaying effect of postharvest bamboo shoot lignification by melatonin treatment was mainly attributed to decreased activity of lignin biosynthesis-related enzymes and induced activation of antioxidant enzyme activity. Moreover, exogenous melatonin may be involved in the transcriptional regulation of the lignification process of bamboo shoots.