Integration of the transcriptome and proteome provides insights into the mechanism calcium regulated of Ulva prolifera in response to high-temperature stress

Abstract

Heat stress is one of the most remarkable abiotic factors limiting the growth and productivity of Ulva prolifera. The calcium signalling pathway plays an important role in the plant heat resistance response. However, the physiology and molecular mechanisms by which the calcium signalling pathway regulates the U. prolifera response to high temperature remain largely unknown. Changes in the physiology, transcriptome, and proteome of U. prolifera in response to high temperature were investigated with exogenous application of CaCl2 (denoted UpCa) and the calmodulin (CaM) inhibitor W-7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride, denoted UpW7) to fill this gap. In total, 33,475 differentially expressed genes (DEGs) and 869 differentially expressed proteins (DEPs) were identified between the control and UpCa treatments. At the mRNA level, the upregulated DEGs were enriched in the RNA transport, mRNA surveillance, carotenoid biosynthesis, basal transcription factor, porphyrin and chlorophyll metabolism, diterpenoid biosynthesis, and flavonoid biosynthesis pathways. The downregulated DEGs were enriched in photosynthesis, plant hormone signal transduction, photosynthesis-antenna proteins, and oxidative phosphorylation. At the protein level, upregulated proteins were enriched in alpha-linolenic acid metabolism, photosynthesis-antenna proteins, and plant–pathogen interactions. The downregulated proteins were enriched in endocytosis, mismatch repair, ribosomes, RNA degradation, and spliceosomes. The addition of exogenous CaCl2 induced the expression of peroxidase, heat shock 70, heat shock 90, nuclear pore complex protein Nup62, MFS transporter, calcium-dependent protein kinase, calcium/calmodulin-dependent protein kinase kinase 1, calcium-binding protein calmodulin-like (CML), Ca2+-transporting ATPase, and serine/threonine-protein kinase at both the mRNA and protein levels. In addition, the same downregulated DEPs and DEGs were correlated and included the ApaG protein, chaperonin GroEL, proteasome inhibitor subunit 1 (PI31), serine/arginine repetitive matrix protein 1, glutamine synthetase, and F-type H+-transporting ATPase subunit alpha. The addition of W7 inhibited Ca2+-related gene expression, and the expression of genes and proteins involved in phagosome, photosynthesis-antenna proteins, RNA transport, plant–pathogen interactions, protein processing in the endoplasmic reticulum, and protein export were downregulated. However, exogenous CaCl2 and W7 increased the expression of TFs, such as Myb and G2-like. In a subsequent study, the addition of CaCl2 significantly increased and W7 significantly inhibited catalase and superoxide dismutase activity in U. prolifera under high-temperature stress. The expression of the CaM gene was significantly increased at 24 h in U. prolifera under high-temperature stress; CaCl2 and W7 significantly inhibited the expression of the CaM gene.In summary, Ca2+ activated Ca2+-related channels to regulate downstream transcript and response proteins; however, the addition of Ca2+ and W7 inhibited photosynthesis. These results provide insights into the mechanism by which calcium increases the mechanical strength of U. prolifera in response to high-temperature stress.