Trihelix transcription factors are involved in drought stress response of Mangifera indica

Trihelix transcription factors (THs) are plant-specific regulators known to play important roles in development and abiotic stress responses. Although extensively studied in several crops, the Trihelix gene family has not yet been characterized in Mangifera indica (mango), a tropical fruit tree highly sensitive to drought stress.

In this study, a total of 49 Trihelix genes (MiTHs) were identified in the Mangifera indica genome. These genes were classified into six subfamilies i.e., GT-1, GT-2, GT-γ, GT-δ, SIP1, and SH4 based on phylogenetic relationships with orthologs from model plants. The MiTH genes were unevenly distributed across 19 chromosomes and exhibited diverse exon-intron structures, motif organizations, and physicochemical properties. Segmental duplication was found to be the primary driver of gene family expansion, and Ka/Ks analysis indicated strong purifying selection pressure acting on duplicated gene pairs. Promoter analysis revealed numerous cis-regulatory elements linked to drought, hormone, and light responsiveness. Expression analysis under drought stress (24 h, 48 h, and 72 h) identified 16 MiTH genes with significant differential expression. Among them, MiTH1 and MiTH6 were consistently upregulated, suggesting a potential role in drought tolerance.

This study presents the first genome-wide analysis of the Trihelix transcription factor family in M. indica, providing key insights into their evolutionary history, structural features, and stress-related expression. The identification of drought-responsive MiTH genes lays a valuable foundation for further functional studies and for developing stress-resilient mango cultivars through molecular breeding or genetic engineering.