Transcriptome Analysis Highlights Key Differentially Expressed Genes Involved in Autolysis Process in Polychaete Perinereis aibuhitensis

Perinereis aibuhitensis belongs to Annelida, Polychaeta, and mainly lives in intertidal zones along the coast of China and several Southeast Asian countries. The P. aibuhitensis has a similar autolysis phenomenon to sea cucumbers, both of which belong to predeath autolysis. This study aimed to investigate the autolysis pathway and reveal the autolysis mechanisms of P. aibuhitensis. The second-generation transcriptomes of the P. aibuhitensis at different stages of autolysis were sequenced and analyzed and the authenticity of the transcriptomic data was verified by real-time fluorescence quantitative PCR (RT-qPCR). A total of 78,653 unigenes were obtained after sequencing, including 1495 differentially expressed genes (DEGs) in the P0h vs. P72hDS (drilled sandworms) groups, 1995 DEGs in the P0h vs. P72hUD (undrilled sandworms) groups and 34 DEGs in the P72hDS vs. P72hUD. The DEGs were mainly concentrated in ECM–receptor interaction (collagen alpha-5[IV], collagen alpha-1[I], agrin), apoptosis-multiple species (caspase-7, bcl-2, baculoviral IAP repeat-containing protein 5-like, septin-5), arachidonic acid (AA) metabolism pathways (carbonyl reductase [NADPH] 1, glutathione (GSH) peroxidase-like, thromboxane-A synthase, secretory phospholipases A2) and metabolism of xenobiotics by cytochrome P450 (CYP450; glucuronosyltransferase, GSH S-transferase, CYP450 family 1 subfamily A1, teroid 17-alpha-hydroxylase, alcohol dehydrogenase). These DEGs were related to cell morphology, cell apoptosis, antioxidant defense response, material and energy metabolism, nerve and muscle damage, etc. In addition, endogenous proteases such as HYAL1 and matrix metalloproteinase-9 (MMP9) were also found to have significant differences between P0h and P72h groups. Four DEGs were screened and subjected to RT-qPCR detection, which confirmed the accuracy of the transcriptome results and also suggested that these genes were closely related to autolysis in P. aibuhitensis. All these results provide a basis for the study of the autolysis process and related genes in P. aibuhitensis and also contribute to the study of the autolysis mechanism in other marine animals.