Genome-Wide Identification and Characterization of the JMJ Histone Demethylase Gene Family in Maize (Zea mays L.) and Its Potential Role Under Drought Stress

Drought stress is a major abiotic factor limiting maize yield and stability. Although Jumonji C (JMJ) histone demethylases are known to regulate plant growth, development, and stress responses, their systematic characterization in maize has remained limited. Here, 27 ZmJMJ genes were identified in the maize genome through BLAST and conserved-domain analyses and classified into five subfamilies: JMJD6, KDM3/JHDM2, KDM4/JHDM3, KDM5/JARID1, and JmjC domain-only. Members within the same subfamily showed similar physicochemical properties, domain composition, and motif distribution, whereas clear divergence was observed among subfamilies. Chromosomal mapping revealed that ZmJMJ genes were unevenly distributed across nine chromosomes, with two interchromosomal homologous gene pairs, suggesting roles for segmental and/or whole-genome duplication in family expansion. Promoter analysis indicated widespread enrichment of elements related to light responsiveness, growth and development, and hormone and stress responses. Expression profiling showed that most ZmJMJ genes were highly expressed in leaves, while several displayed tissue specificity. Under drought stress, ZmJMJ17a, ZmJMJ17b, ZmJMJ28, and ZmJMJ32 were significantly induced, highlighting them as promising candidates for functional studies and molecular breeding for drought tolerance in maize. This study provides a foundation for elucidating the evolution and functions of the ZmJMJ family and identifies candidate genes for drought-related functional validation and molecular breeding.