Analysis Transcriptome Of Pyropia Haitanensisunder High Light Stress

Pyropia haitanensis is a particular economically important marine crop in southern China,also the representative species at intertidal for researches on algal stress resistance.P.haitanensis experiencing strength ligh when living in the intertidal zone due to tide cycle,which resulted in the photosynthesis P.haitanensis was been impacted.So,a study on response mechanism to high light stress could help to maintain sustainable development of P.haitanensis industry.In this study,we selecting the P.haitanensis Z-61 strain as materials,through high-throughput transcriptome sequencing under different levels of light conditions(50,200,500,1000 and1000II?mol/(m~2·s)),to selecte a number of candidate genes related with high light tolerance.At the same time,this study investigated the photosynthetic efficiency,photosynthetic pigment contents and antioxidant system.We preliminary analyzed the response mechanism to high light stress in P.haitanensis.The main results are as follows:1.The results of physiological and biochemical level indicates that P.haitanensis blades were remarkably inhibited by high light stress,and the ROS clearance systems could not completely remove the reactive oxygen species,thus lead to damage on membrane lipid oxidative.2.Under different light intensity levels of P.haitanensis using Illumina technology throughput transcriptome sequencing,32,140 unigenes with an average length of 639.25 bp were obtained and the GC percentage was 70.25%and N50 value was 898.Though comparison with public database,in total of 8,917 genes were functionally annotation.Include antioxidant enzyme systems,heat shock protein chaperones,transcription factors and other stress-related genes,and photosynthetic related genes,such as P450 type cytochrome,light harvesting protein and high light induced protein.3.Primer of six candidate genes(UBC,EF2,GADPH,TUB,ACT,18S)were designed according to transcriptome unigene sequence,their expression at different levels of light intensity were determined using fluorescence quantitative PCR to assess the expression stabilities(geNorm software,NormFinder software and comparative C_T method).UBC was the most stable housekeeping gene and GADPH was the most unstable one.Then UBC was the optimal internal reference for qRT-PCR validation of P.haitanensis under different light levels.4.Statistical analysis of gene expression of P.haitanensis under four light conditions shown that a large number of gene undergone significant changes.Thought pathway significant enrichment analysis,this study found the main metabolic pathways involved in response to high light were the glycolysis,oxidative phosphorylation,photosynthesis,amino acid biosynthesis,carbon metabolism,nitrogen metabolism and PI3K-Akt-mTOR signaling pathway,etc.5.The possible regulate process of P.haitanensis response high light stress may be induced photoinhibition and then chloroplast freed excessive ROS under high light intensity stress.On the one hand,ROS caused P.haitanensis membrane lipid oxidative damage;On the other hand,P.haitanensis cells awake autophagy under high light intensity stress,the ROS as signaling molecules that activate PI3K phosphorylation role of Akt,and Akt activation its downstream molecular mTOR it make substrate phosphorylation,then acting on ribosomal protein S6E,thereby,inhibiting cells occur to excessive autophagy.The results showed that,PI3K-Akt-mTOR signaling pathway in response high light intensity stress plays a crucial role in P.haitanensis.