Metabolome analysis reveals the involvement of oxylipins in regulating the maturation of conchosporangia in Pyropia haitanensis

Abstract

In Porphyra sensu lato, the development of the conchocelis into conchosporangia depends on a suite of environmental factors. This process is not entirely controllable, a situation that to some extent has limited the development of the seaweed industry. To understand the mechanisms underlying this process, changes in the cellular morphology of Pyropia haitanensis were recorded, and the structural differences between conchocelis and conchosporangia were observed using transmission electron microscopy. Metabolome analysis was employed to compare the metabolite profiles throughout the development of the conchosporangia. The results showed significant differences in cell morphology between conchocelis and conchosporangia, with conchosporangia cells exhibiting increased diameters due to apical swelling and growth. Within the cells, the number of vacuoles and the amount of floridean starch were increased, while the cell walls and mucilage layers became thickened. Metabolome analysis indicated that the lipoxygenase (LOX) pathway was likely involved in the formation of conchosporangia, with oxylipins derived from C18 and C20 being abundant during maturation. Oxylipins such as oxo-eicosatetraenoic acid (KETE), methyl jasmonic acid (MeJA), and prostaglandins were significantly increased during maturation. PhLOX genes related to oxylipin synthesis showed differential expression throughout the maturation process. Additionally, the exogenous application of MeJA and 5-KETE enhanced the formation of conchosporangia. Overall, the results suggest that the LOX pathway may play a key role in regulating the maturation of conchosporangia in Porphyra sensu lato. and that oxylipins could potentially be used as industrial seedling regulators.