Genetic Variation and Gene Expression of the Antimicrobial Peptide Macins in Asian Buffalo Leech (Hirudinaria manillensis)

With the growing severity of antibiotic resistance, antimicrobial peptides demonstrate significant potential for medical applications. Here, we performed genome and transcriptome sequencing of 30 Asian buffalo leech (<i>Hirudinaria manillensis</i>) individuals and integrated data from three other leech species (<i>Whitmania pigra</i>, <i>Hirudo nipponia</i>, and <i>Hirudo medicinalis</i>) to investigate genetic variation and gene expression of <i>H. manillensis</i> macins. Three macins (Hman1, Hman2, and Hman3), along with their encoding genes (<i>Hman1</i>, <i>Hman2</i>, and <i>Hman3</i>), were identified in <i>H. manillensis</i>. Hman1 exhibited the highest similarity (63.5 ± 12.0%) to macins from other leeches, followed by Hman2 (57.8 ± 7.4%) and Hman3 (30.0 ± 3.5%). Both amino acid and codon sequences of Hman1 were conserved within the species, whereas Hman2 and Hman3 exhibited markedly higher variability. All <i>Hman1</i> sequences were translatable, while four <i>Hman2</i> and 28 <i>Hman3</i> sequences had degenerated into pseudogenes. Transcripts per million (TPM) values for <i>Hman1</i>, <i>Hman2</i>, and <i>Hman3</i> were 2196.63, 242.35, and 1.22, respectively. Total macin expression in <i>H. manillensis</i> was less than 1/20 of that in <i>W. pigra</i>. Based on sequence variation and expression patterns, we propose that Hman1 retains functionality while Hman2 and Hman3 have lost or are losing their antibacterial functions.