Comprehensive analysis of TGA genes in barley: structure, evolution, and stress-responsive expression.

Area of Science:

• Plant Molecular Biology
• Genomics
• Biochemistry

Background:

• TGA transcription factors (bZIP family) are crucial for plant hormone signaling and stress responses.
• Limited information exists on the genomic organization and regulatory functions of TGA factors in barley (Hordeum vulgare L.).

Purpose of the Study:

• To conduct a comprehensive genome-wide characterization of TGA transcription factors in barley.
• To elucidate their evolutionary relationships, structural diversity, and regulatory mechanisms involved in stress and hormone responses.

Main Methods:

• Genome-wide identification and phylogenetic analysis of HvTGA genes.
• Analysis of gene duplication events and selection pressures (Ka/Ks ratios).
• Promoter analysis for cis-regulatory elements and miRNA target prediction.
• Protein-protein interaction network construction and functional enrichment analysis.
• Expression profiling under various abiotic stress conditions.

Main Results:

• Identified 49 HvTGA genes, with specific chromosomal clusters and four distinct phylogenetic clades.
• Segmental and dispersed duplications were major drivers of gene expansion, under purifying selection.
• Promoter regions contain elements for hormone (ABA, SA, JA) and stress responses; 31 miRNAs target 29 HvTGAs.
• HvTGA-29, HvTGA-43, and HvTGA-41 showed robust induction under multiple abiotic stresses (heat, salt, osmotic).
• HvTGA genes are involved in transcriptional regulation, hormone signaling, MAPK pathways, and carotenoid biosynthesis.

Conclusions:

• This study provides the first genome-wide characterization of barley TGA transcription factors.
• Uncovered significant structural diversity, evolutionary insights, and complex regulatory networks.
• HvTGA-29, HvTGA-43, and HvTGA-41 are proposed as key candidates for enhancing stress and hormone responsiveness in barley.