{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T15:11:04Z","timestamp":1788966664268,"version":"build-2803163510"},"reference-count":26,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T00:00:00Z","timestamp":1788912000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Natural Science Foundation of Rizhao","award":["RZ2024ZR26"],"award-info":[{"award-number":["RZ2024ZR26"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biology"],"abstract":"<jats:p>Lumbricin, a classic proline-rich antimicrobial peptide (PrAMP), has been primarily characterized in terrestrial clitellates, with limited reports in other annelid lineages, leaving a critical knowledge gap regarding its presence and immune roles in marine invertebrates. The echiuran worm Urechis unicinctus lives in microbe-laden intertidal mudflats and depends on innate immunity against pathogens, yet its lumbricin homologs have remained unreported. In this study, we aimed to clone full-length lumbricin cDNA and systematically characterize its molecular traits, tissue distribution, LPS (lipopolysaccharide)-triggered transcription and in vitro antibacterial function. Sequence analysis showed the deduced 67-amino-acid U. unicinctus lumbricin contained 10.4% proline and lacked a signal peptide, retaining the conserved N-terminal cationic patch and C-terminal motifs of earthworm lumbricins. Phylogenetic analysis confirmed its close evolutionary linkage to Eisenia andrei lumbricin-related peptide. Quantitative PCR (qPCR) detected ubiquitous constitutive expression, peaking in the body wall, followed by the hindgut and midgut. LPS induced rapid 3 h upregulation in the body wall for acute local defense, with massive late-stage elevation at 48 h in the hindgut, anal sacs and coelomic fluid. Recombinant lumbricin exerted broad-spectrum growth-inhibitory effects against Gram-positive and Gram-negative bacteria. This study is the first to identify a functional lumbricin homolog in marine non-clitellate annelids (echiurans), which expands the taxonomic range of the lumbricin family and provides new insights into innate immune defense of marine benthic organisms.<\/jats:p>","DOI":"10.3390\/biology15181590","type":"journal-article","created":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T14:02:48Z","timestamp":1788962568000},"page":"1590","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Molecular Cloning and Functional Analysis of Lumbricin in Urechis unicinctus"],"prefix":"10.3390","volume":"15","author":[{"given":"Xiuling","family":"Sun","sequence":"first","affiliation":[{"name":"School of Life Sciences, Jining Medical University, Rizhao 276800, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"}]},{"given":"Lihuan","family":"Sun","sequence":"additional","affiliation":[{"name":"School of Life Sciences, Jining Medical University, Rizhao 276800, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"}]},{"given":"Mengjing","family":"Fan","sequence":"additional","affiliation":[{"name":"School of Life Sciences, Jining Medical University, Rizhao 276800, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"}]},{"given":"Yuxin","family":"Li","sequence":"additional","affiliation":[{"name":"School of Life Sciences, Jining Medical University, Rizhao 276800, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"}]},{"given":"Litao","family":"Zhang","sequence":"additional","affiliation":[{"name":"School of Life Sciences, Jining Medical University, Rizhao 276800, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"50","DOI":"10.1016\/j.micpath.2017.11.039","article-title":"Fish antimicrobial peptides (AMP\u2019s) as essential and promising molecular therapeutic agents: A review","volume":"114","author":"Shabir","year":"2018","journal-title":"Microb. 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