Genome-Wide Identification, Evolutionary Characterization, and Salt-Stress Expression Profiling of Antimicrobial...

Background/Objectives: Antimicrobial peptides (AMPs) contribute to plant innate immunity and abiotic-stress adaptation, but their repertoires remain poorly characterized in extremophytic plants. We aimed to define AMP gene families and their expression under Na₂SO₄ treatment in the xerophytic recretohalophyte Reaumuria soongarica. Methods: Six canonical AMP families were screened using hidden Markov model and homology searches, domain verification, gene-model and transcript-support assessment, nsLTP boundary curation, phylogenetic and synteny analyses, and reanalysis of public RNA-sequencing data from 0, 200, and 400 mM Na₂SO₄ treatments. Results: We identified 73 candidates: 15 defensins, 18 Snakin/GASA genes and 40 nsLTPs, including seven previously unannotated, transcript-supported models. RsLTP20 was reported separately as a reference-dependent C4-like candidate. Four sequence and alignment strategies supported two defensin, one Snakin/GASA and three nsLTP local groups. No tested promoter pattern was significantly enriched after multiple-testing correction. At 400 mM Na₂SO₄ relative to the control, 18 of the 66 catalogue members represented in the quantification reference were differentially expressed (12 upregulated and six downregulated; BH-adjusted p < 0.05 and |log₂ fold change| > 1). Comparison with 38 Tamarix austromongolica candidates identified 27 reciprocal-best-hit pairs; genomic collinearity supported 25 direct candidate pairs. A separate Arabidopsis comparison recovered 26 candidate-anchored pairs. Conclusions: This curated catalogue defines conservative phylogenetic groups and provides candidates for experimental analysis of stress adaptation and peptide function.