Abstract
Background: The DMPs (DOMAIN OF UNKNOWN FUNCTION 679 membrane proteins) constitute a plant-specific protein family that plays essential roles in reproductive development, senescence, and diverse physiological processes. Despite their importance, limited information is available on DMP genes in Chinese cabbage (Brassica rapa). To address this, we conducted a genome-wide identification and characterization of the DMP gene family in Chinese cabbage, followed by analyses of their structural features, evolutionary relationships, and expression patterns. Results: A total of 16 BrDMP genes were identified, unevenly distributed across 10 chromosomes. Most BrDMP genes contained a single exon without introns. Evolutionary analyses revealed 3 tandem and 6 segmental duplication events, while phylogenetic analysis classified the family into five subfamilies, with Subfamily III being the largest (6 members). BrDMP proteins displayed distinct monocot- and dicot-specific clustering patterns. The qRT-PCR demonstrated pronounced organ-specific expression, particularly in root, stamen, and big bud. Moreover, the majority of BrDMP genes were differentially regulated under abiotic stresses (drought, salt, cold, heat) and by exogenous plant hormones (ABA, tZ, NAA). Notably, BrDMP9A and BrDMP9B (Subfamily IV) shared strong similarity with haploid induction genes reported in Arabidopsis thaliana, maize, and Brassica napus. These genes showed elevated expression in big bud and stamen, localized to the cell membrane, and were able to partially rescue the seed abortion phenotype in the A. thaliana dmp8 dmp9 double mutant. Conclusions: This study provides the first comprehensive characterization of the DMP gene family in Chinese cabbage. Our findings not only advance understanding of BrDMP gene functions but also identify BrDMP9A and BrDMP9B as strong candidates for developing DMP-based haploid inducer lines, offering direct applications for accelerating doubled-haploid breeding in Brassica crops.