Genome-Wide Identification and Expression Analysis of the ARF Gene Family in Chickpea (Cicer arietinum)

Leaf architecture critically impacts crop yield. The Auxin Response Factor (ARF) family is a key regulator of leaf development, yet remains uncharacterized in the important legume crop chickpea (Cicer arietinum L.), which bears pinnate compound leaves. Here, we performed a genome-wide identification and analysis of ARF genes in chickpea. We identified 33 CaARF genes and resolved their phylogenetic structure through comparison with six other key dicot species. The analysis revealed a deeply conserved core set of ARF proteins across species, all sharing the N-terminal DNA-binding domain (DBD), with most the C-terminal PB1 domain, connected by a middle region (MR). We also uncovered instances of lineage-specific expansion, e.g., a chickpea-specific ARF clade, which is characterized by the absence of the C-terminal PB1 domain. Expression profiling using public transcriptome data and qRT-PCR revealed distinct spatiotemporal expression patterns for CaARF genes across tissues and during compound leaf development. Detailed in situ hybridization analysis for selected candidates, chosen based on phylogenetic proximity to known leaf-development-related ARFs in other species, localized their transcripts to specific regions within compound leaf primordia. Focusing on CaARF5, the closest ortholog of Arabidopsis MONOPTEROS/ARF5, we confirmed its nuclear localization and dynamic expression during chickpea leaf development. Functional complementation assays demonstrated that CaARF5 could restore developmental defects in the Arabidopsis mp mutant. Our study establishes an evolutionary and molecular framework for the chickpea ARF family, highlighting conserved features and species-specific innovations, and provides essential resources for future research on auxin-mediated leaf development and ARF-targeted legume breeding.