Genome-wide identification and expression pattern analysis of auxin response factor (ARF) genes in Chionanthus retusus and functional characterization of CrARF37 in terms of its effect on flower shape.

BACKGROUND

The Auxin Response Factor (ARF) gene family is ubiquitous in the plant kingdom, serving as a pivotal gene in the auxin signaling pathway. Members of this gene family encode transcription factors that regulate diverse aspects of plant growth and development. Notably, the Class IIa and Class IIb subfamilies within the ARF gene family play a vital role in plant flower development and morphogenesis. Chionanthus retusus, as significant ornamental plants in gardens, exhibit multiple flower forms, and changes in these forms have garnered substantial attention in the selection and cultivation of new varieties.

RESULT

In this study, we utilized the latest reference genome to conduct a comprehensive identification and analysis of the ARF gene in C. retusus (2n = 2x = 46), and examined its expression patterns in individuals with varying flower morphologies and generated transgenic Arabidopsis overexpressing CrARF37 and analyzed its function in flower morphogenesis. We identified 49 ARF genes in C. retusus, which can be categorized into four subfamilies and are distributed across 18 chromosomes. Genomic collinearity analysis demonstrated their conservation across evolution, and gene structure, domain, and motif analyses further confirmed their structural conservation. Ultimately, based on expression patterns in individuals exhibiting various flower morphologies, we identified CrARF32, CrARF37, and CrARF39 as potential contributors to the formation of C. retusus flower morphology. Subsequently, we generated CrARF37-overexpressing transgenic Arabidopsis, and phenotypic analysis revealed significantly increased length and number of flower veins compared to controls.

CONCLUSION

Based on gene family analysis, transcriptome gene co-expression network, and transgenic functional validation, we identified three ARF genes that may be associated with differences in C. retutus flower morphology. In addition, we validated the transgenic function to elucidate how CrARF37 affects the development of floral vascular tissue.Our findings will enhance our understanding of flower morphological development and provide valuable theoretical insights for Osmanthus cultivation.