Interactions between nitrogen and phosphorus modulate the food quality of the marine crop Pyropia haitanensis (T. J. Chang & B. F. Zheng) N. Kikuchi & M. Miyata (Porphyra haitanensis)

The quality of Pyropia haitanensis (T. J. Chang & B. F. Zheng) N. Kikuchi & M. Miyata (Porphyra haitanensis) is directly affected by nutrient availability. However, the molecular mechanism underlying the synergistic regulatory effects of nitrogen (N) and phosphorus (P) availability on P. haitanensis quality is unknown. Here, we performed physiological and multi-omics analyses to reveal the combined effects of N and P on P. haitanensis quality. The pigments accumulated under high N because of increases in N metabolism and porphyrin metabolism, ultimately resulting in intensely colored thalli. High N also promoted amino acid metabolism and inosine 5′-mononucleotide (IMP) synthesis, but inhibited carbohydrates accumulation. This resulted in increased amino acid, IMP and decreased agaro-carrageenan and cellulose contents, thereby improving the nutritional value and taste. Furthermore, high P promoted carbon metabolism and amino acid metabolism.This study provided the basis for elucidating the mechanism behind N and P regulating the seaweed quality.