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.

The establishment of dorsoventral polarity is a critical step in leaf morphogenesis, enabling the transition from radial primordia to flattened laminae. The MYB domain transcription factor ASYMMETRIC LEAVES1 (AS1) plays a central role in this process by regulating leaf polarity and developmental transitions, primarily through the repression of Class I KNOX genes. Here, four AS1 paralogs were identified in soybean (Glycine max), two of which showed collinearity with Arabidopsis thaliana and Medicago truncatula. The AS1 proteins of soybean and Arabidopsis exhibit high conservation, whereas the four GmAS1 genes in soybean display different tissue-specific expression patterns. Strikingly, each GmAS1 gene was able to fully rescue the defective phenotype of the Arabidopsis as1 mutant, indicating that GmAS1 genes are functionally conserved in leaf polarity regulation. Promoter analysis further indicated that GmAS1 genes are enriched in cis-acting elements related to light response, hormone regulation, development, and stress response, suggesting potential subfunctionalization among these paralogs. In conclusion, these findings demonstrate that GmAS1 genes are evolutionarily conserved in function but potentially diversified in regulation, providing new insights into their role in leaf polarity and stress adaptation.