Zhourui Liang1, 3, Xiao Wang1, Pengyan Zhang1, 3, Wenjun Wang1, 3, Fuli Liu2, 3, *
1 Key Laboratory of Sustainable Development of Marine Fisheries, Ministry of Agriculture, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, 266071, China.
2 Key Laboratory of Marine Genetics and Breeding, Ministry of Education; College of Marine Life Science, Ocean University of China, Qingdao, 266102, China
3 Laboratory for Marine Fisheries and Aquaculture, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, 266237, China.
The delayed gametophyte of kelp, keeping continuous vegetative growth rather than gametogenesis under unsuitable conditions, could restart the gametogenesis under suitable conditions. To gain more insights into the process and mechanism of gametogenesis of delayed gametophyte in S. japonica, the ultrastructure, photosynthetic and biochemical response, and dynamics of gene expression at four time points during gametogenesis were investigated in this study. After gametogenesis induction, there were significant changes in the ultrastructure, including the increasing of mitochondria and Golgi, the changing of chloroplast structure, the further developing of endoplasmic reticulum. The contents of ABA and H2O2, the activities of pivotal respiratory enzymes, as well as the key antioxidant enzymes all increased significantly after 3 d of gametogenesis induction, implying these changes were closed related to the transition of gametophyte from vegetative growth to gametogenesis. It was noteworthy that the photosynthetic and respiratory indicators all showed significantly up-regulated trend after 6 d of induction, indicating that the metabolism of gametophyte was most active during transforming from vegetative growth into gametogenesis. A total of 37048 time-specific DGEs were identified during the vegetative and reproductive process of gametophyte, among which cell part, cellular process, and binding categories accounted for the most frequent groups. Most of the identified DEGs encoded members of the bHLH, MYB, and C3H transcription factor families. There were 8 genes relating peroxisome, 12 genes relating proteasome, 4 genes relating oxidative phosphorylation, and 59 genes relating ubiquitin mediated proteolysis identified as up- or down-regulated DEGEs at the two key stagesduring gametogenesis.