Genome-Wide Characterization and Identification of Auxin Response Factor (ARF) Gene Family Reveals the Regulation of RrARF5 in AsA Metabolism in Rosa roxburghii Tratt. Fruits

<i>Rosa roxburghii</i> Tratt., a fruit crop known for its high Vitamin C content and other nutritional compounds, has not yet been studied for its <i>auxin response factor</i> (<i>ARF</i>) family members. ARFs are important proteins in auxin-mediated pathways, playing a vital role in plant physiological and biochemical processes such as plant development, and flower and fruit maturation. In the present study, we identified 14 <i>ARF</i> genes (designated as <i>RrARFs</i>) in <i>R. roxburghii</i>, which are distributed across seven chromosomes and grouped into four subfamilies. An analysis of cis-acting elements revealed that these genes might be involved in various biological processes, including plant development, flower development, light responses, cell cycle regulation, phytohormone responses, and responses to abiotic and biotic stresses. A gene expression analysis demonstrated differential expression of <i>RrARF</i> genes across different tissues and stages of fruit development, with four members showing higher expression during the fruit ripening stages. Furthermore, a coexpression analysis identified that <i>RrARF5</i> was highly coexpressed with <i>RrMDHAR1</i>, a key enzyme involved in Vitamin C biosynthesis. Moreover, transactivation assays and transient overexpression experiments confirmed that RrARF5 activates the transcription of <i>RrMDHAR1</i>. The findings of this study suggest a potential role of the <i>ARF</i> gene family in Vitamin C accumulation in R. roxburghii and enhance our understanding of the diverse regulatory function of the <i>ARF</i> gene family in plants.