Metabolic Response Mechanism Of Corals To High Temperature Stress Based On Mass Spectrometry Metabonomics

Coral reef ecosystem,as the most prominent and representative ecosystem in tropical ocean,has a high biodiversity.However,in the context of global warming,coral bleaching is becoming increasingly serious,leading to the rapid degradation of coral reef ecosystems worldwide.Exploring the molecular mechanism of coral symbionts responding to high temperature stress is vital important for the protection and restoration of coral reef ecosystem.Metabonomics,which is closest to phenomics,can reflect the physiological effects of environmental factors on organism and has the advantage of amplifying small changes in gene and protein expression.This paper is divided into two parts: in the first part,four coral species,Pocillopora Meandrina,Seriatopora hystrix,Montipora digitata and Fungia fungites from Paracel Islands,China,were selected for the study.By optimizing the extraction conditions of metabolites and the parameters of data processing software MZmine2 and Compound Discoverer,a method for the analysis of Coral metabolomics was established;Untargeted mass spectrometry metabonomics combined with Global Natural Products Social Molecular Networking(GNPS)was used to analyze the metabolites of corals,and a database of coral metabolites was established.In the second part,Pavona decussata collected from Weizhou Island,Guangxi,China,we used as model species to explore the metabolic response mechanism of coral to heat stress with the established method.The experimental methods were as follows: cultivate and build the bleached coral model indoor,and the metabolic extracts of the coral symbiont were characterized by highperformance liquid chromatography and high resolution mass spectrometry,then61 differential compounds were screened and identified by multivariate statistical analysis and GNPS.The metabolic pathways about the differential compounds were analyzed.The main findings are as follows:The results showed that the contents of lipids,fatty acids,peptides,amino acids and other metabolic small molecules changed during coral bleaching.The conclusions included: 1)numerous metabolites in the classes of lipids(e.g.betaine lipids,monogalactosylmonoacylglycerol(MGMG),and digalactosylmonoacylglycerol(DGMG)),fatty acids and their derivatives(e.g.fatty acid methyl ester(FAME)),and amino acids(e.g.glutamine and glutamate)significantly decreased,indicating an enhanced lipid hydrolysis and aminolysis that contributed to up-regulation in gluconeogenesis to meet energy demand for coral’s basic survival;2)pantothenate and panthenol,two essential intermediates in tricarboxylic acid(TCA)cycle,were up-regulated,implying enhanced efficiency in energy production;3)small peptides(e.g.Glu-Leu and Glu-GluGlu-Glu)were accumulated,indicating an enhanced antioxidant response;4)lyso-platelet-activating factor(lyso PAF)C-16 and lyso PAF C-18 were downregulated,implicating the strengthened immune response of coral;5)osmolytes of betaine and trimethylamine N-oxide(TMAO),which serve to maintain symbiont homeostasis,were down-regulated.