Identification and Expression Analysis of CCCH Zinc Finger Proteins in Mulberry (Morus alba)

CCCH zinc finger proteins play critical roles in plant growth, development and stress responses. Here, 56 CCCH genes were identified in Morus alba. These genes displayed wide variation in coding sequence (456-6318 bp) and protein length (151-2105 aa), with most proteins predicted to localize in the nucleus and a few in chloroplasts, the endoplasmic reticulum or cytoplasm. Chromosomal mapping showed uneven distribution across 14 chromosomes, with tandem clusters on chromosomes 1, 6 and 13. Phylogenetic analysis classified 53 MaC3Hs into 13 subfamilies, while three genes remained ungrouped. Synteny analysis revealed four segmental duplication events, suggesting segmental duplication as the major expansion mechanism, under purifying selection. Comparative collinearity showed higher conservation with Arabidopsis thaliana than with rice or maize. Promoter analysis identified 22 cis-acting elements, mainly related to phytohormones, followed by abiotic stress and developmental regulation. Expression profiling under drought stress revealed differential expression across tissues, with MaC3H33 showing strong induction (>200-fold in stems on day 6). Subcellular localization confirmed MaC3H33 is nuclear, and yeast assays indicated no self-activation. These findings provide comprehensive insights into the MaC3H gene family and lay a foundation for functional studies related to drought tolerance in mulberry.