Molecular Mechanism Of Low Temperature Adaptation Of Invasive Tubule Snails Based On Transcriptomics

Pomacea canaliculata is one of the world's 100 worst invasive alien species.It was introduced into mainland China in 1981 as a high-protein economic culture variety.Due to its strong adaptability,rapid growth,and short reproductive cycle,it quickly formed natural populations and became a serious agricultural pest in most provinces of south of the Yangtze River in China.In 2003,it was listed as "China's First Batch of Invasive Alien Species List" by the former State Environmental Protection Administration,and in 2012,it was listed as China's first batch of national key invasive alien organisms under national management by the former Ministry of Agriculture.In addition,another invasive species of P.maculata,also exists in mainland of China.Studies have shown that this species could improve the cold tolerance and the overwintering survival rate through cold acclimation.However,the molecular mechanism of cold acclimation to improve the cold tolerance of P.canaliculata are not clear.In the present study,the cold acclimation treatment was carried out on the P.canaliculata,and the transcriptome of hepatopancreas was compared before and after cold acclimation and low temperature stress,in order to reveal the molecular mechanism of cold acclimation in improving the cold tolerance of P.canaliculata.It provided an important theoretical basis for further research on the invasion mechanism and development of the prevention and control methods of P.canaliculata and P.maculata.The results of this study mainly include the following three parts:1.Transcriptome sequencing was used to screen the differentially expressed coding genes in the hepatopancreas of P.canaliculata before and after cold acclimation and low temperature stress.The results showed that cold acclimation,through metabolic adjustment,activated the ubiquitin-proteasome system to degrade damaged or misfolded proteins,reduced oxidative stress injury,increased the content of unsaturated fatty acids and cholesterol,and improved the cold tolerance of P.canaliculata.The adaptive evolution of genes in the degradation of damaged proteins,the stability of cytoskeleton,and the maintenance of ion balance may be the reason for the cold tolerance of P.canaliculata higher than that of P.maculata.2.There were 5915 long non-coding RNAs(lncRNAs)reidentified by transcriptome sequencing,most of which were intergenic lncRNAs.Compared with mRNA,lncRNA is characterized by lower expression level,shorter sequence length and fewer exons.In this study,we found that lncRNA can regulate the expression of E3 ubiquitin protein ligase,26S proteasome non-ATPase-dependent regulatory subunit,glutathione mercaptotransferase synthesis,glutathione S-transferase,and cytochrome P450 protein coding genes to participate in cold acclimation to improve the cold tolerance of P.canaliculata.3.A total of 33 putative DnaJ genes(PcDnaJ)from P.canaliculata were identified through bioinformatics methods.These DnaJ genes were classified into three groups according to the presence of the complete three domains(J-domain,G/F-domain,and zinc finger domain).Chromosome mapping suggested that no segmental duplication and tandem duplication have occurred.The PcDnaJ genes are highly diverse in sequence,domain structure.Expression profiles based on RNA-seq showed that the PcDnaJ genes were expressed in at least one tissue tested.The results suggested that PcDnaJ genes were functionally diverse.Five PcDnaJ genes expression were significantly up-regulated at low temperature stress after cold acclimation relative to the control group.PcDnaJ genes possibly participates in response to cold acclimation improved the cold tolerance of P.canaliculata.Moreover,a strong signature of purifying selection was observed between the comparison of orthologous gene pairs of P.canaliculata and P.maculata.