Adaptive Gene Expression Changes Of The Invasive Seaweed Agarophyton Vermiculophyllum

Invasive species can successfully and rapidly open up new ecological niche and expand their distribution by enhancing their tolerance and adaptability to environmental pressure.However,little is known about the molecular mechanisms that promote rapid adaptation to new environments during species invasion,namely changes in gene expression.The red alga A.vermiculophyllum is native to the northwest Pacific Ocean and has successfully invaded coastal habitats in North America and Europe over the past 100 years.To understand the potential molecular mechanisms of successful invasion of A.vermiculophyllum at the molecular level,we collected population samples from their origin(Japan)and two invading regions(the Del Marva Peninsula in the eastern United States and Germany).The samples were cultured and acclimated in a common garden system for 4months,and then conducted transcriptome(mRNA)and small RNA(miRNA)sequencing.In addition,comparative transcriptome analysis was conducted between A.vermiculophyllum and Gracilariopsis cordata.The main results are as follows:1.The mRNA expression profile identified 59 genes that expressed differently in the algal bodies of the origin and invasion sites.Most of these genes are involved in metabolic pathways,including photosynthesis,abiotic stress,and biosynthesis of products and hormones at four invasion sites.The correlation analysis of target genes based on miRNA revealed that some target genes are positively or negatively regulated through epigenetic mechanisms in the comparison of origin and invasion sites.Importantly,most of these genes are related to metabolism and defense abilities(such as metal transporter Nramp5,aging related proteins,cell wall related hydrolases,ycf68 protein,and cytochrome P450 TBP).2.The GO and KEGG enrichment results of comparative transcriptome data between A.vermiculophyllum and its related species G.cordata showed that compared with G.cordata,the expression of genes related to photosynthesis,carbon fixation and other pathways in A.vermiculophyllum was significantly increased,and the expression of genes controlling retrotransposon and photosystem Ⅱ D1 protein was also significantly increased.The extensive expression of genes related to carbon fixation during photosynthesis may help A.vermiculophyllum to cope with stress,while the increased expression of retrotransposons and photosystem II D1 proteins helps algae repair photosystem II complexes,thereby producing more organic matter for algae growth and development.Therefore,the gene expression results between the populations of the origin and invasion sites of A.vermiculophyllum indicate that resource redistribution during metabolic processes is likely a major mechanism that contributes to the widespread persistence and adaptability of true gracilaria within the invasion range.Based on the comparative transcriptome and miRNA sequencing technology,this study preliminarily discussed the molecular mechanism of the successful invasion of A.vermiculophyllum at the gene expression level.It not only provides a new perspective for us to deeply understand how algae adapt to local environment after invading to a new habitat,but also sheds light on important molecular evidence for intertidal marine organisms in response to environmental changes.