Comprehensive genomic screening and expression profiling of trihelix family in pearl millet under abiotic stresses with emphasis on functional insights of PgTHX24

Abstract

The trihelix transcription factors (THX TFs) play a crucial role in light responses and are involved in plant growth, development, and stress responses. In this study, we have identified 35 trihelix TFs in pearl millet (Pennisetum glaucum), which is one of the most widely grown C4 cereal crops in tropical semi-arid regions. Identified PgTHXs (Trihelix members of P. glaucum) were classified into 5 subgroups (GT1, GT2, GTγ, SH4, and SIP1) based on phylogenetic analysis, and these subgroup members shared similar gene structure and motif distribution pattern. Collinearity analysis exhibited gene duplication events of trihelix family members in pearl millet across the genome. Gene ontology (GO) annotation and cis-regulatory elements (CREs) analysis of PgTHXs suggested their involvement in diverse biological and molecular functions associated with plant growth, development, and stress responses. RNA sequencing data and expression profile displayed differential expression patterns of PgTHXs under abiotic stress and phytohormone treatments. The induced expression pattern of the PgTHX4, PgTHX5, PgTHX24, and PgTHX30 suggested their potential involvement in abiotic stress responses through phytohormonal signalling pathways. Among these, PgTHX24, a GT-3b member, was localized in the nucleus with self-transactivation ability. Overexpression of PgTHX24 positively regulated expression of stress-related markers in transformed pearl millet calli under drought stress conditions. Promoter activity analysis also highlighted the stress-inducible nature of PgTHX24’s promoter. Overall, our findings provide a comprehensive understanding of PgTHXs with a framework for further functional characterization to understand their regulatory role in pearl millet’s growth, development, and stress responses. Key message: Thirty-five trihelix TFs were identified in pearl millet, and a comprehensive expression profile highlighted their functional diversity. Overexpression of PgTHX24 exhibited its potential involvement in abiotic stress responses.

Keywords

• Trihelix transcription factors
• Phylogenetic analysis
• Cis-regulatory elements
• Abiotic stresses
• Pearl millet