## 4 ARF Is Involved in the Regulation of Floral Structure and Sexual Reproduction  
A plant's flowers are essential for its own reproduction and are the organs of sexual reproduction for the vegetation. Over the course of evolution, the flower of a plant has developed into a more stable structure, generally consisting of a stalk, calyx, receptacle, corolla, pistil, and stamens. The stamens and pistils are composed of different parts, with the stamens consisting of the anthers and filaments and the pistils consisting of the style, stigma, and ovary. Flower development, maintenance, abscission process, and the normal formation of pistil and stamen are all crucial for plant growth and fruit formation. It has been extensively reported that auxin response factors play a key regulatory role in these processes.  
Research on the regulatory role of ARF in plant flowers has been carried out mostly in Arabidopsis. [PERSON] et al. [12] reported that AtARF1 and AtARF2 in Arabidopsis affect flower initiation, stamen development, and flower senescence and abscission. arf2 mutant plants show delays in flowering and abscission of floral organs. arf1 mutations enhanced many arf2 phenotypes, indicating that ARF1 acts in a partially redundant manner with ARF2. AtARF3 regulates floral meristem determinacy by repressing cytokinin biosynthesis and signaling, and loss of AtARF3 leads to the development of pistil appearance defects [27]. There are many reports about the crucial roles of MONOPTEROS (MP)/ARF5 in the regulation of flower formation and other activities of shoot apical meristem. For example, [PERSON] et al. [28] uncovered a molecular framework for flower initiation that includes AtARF5 and LEAFY, a master regulator of flower development, which reveals a mechanistic link between flower primordium initiation and subsequent steps in flower morphogenesis. AtARF6 and AtARF8 are thought to control stamen and pistil maturation, respectively, and the loss of a single gene in either ARF6 or ARF8 causes delayed stamen filament elongation and delayed auther dehiscence, resulting in reduced self-pollination. The double mutant, on the other hand, is directly and completely sterile [29]. Another study on AtARF8 stated a simple variant of ARF8 can regulate the elongation of stamens [30]. Uniquely, AtARF17 is essential for pollen wall patterning in Arabidopsis by modulating primexine formation at least partially through direct regulation of _CALLOSE SYNTHASE5_ (_CalS5_) gene expression [31].  
ARF regulation of floral structure and sexual reproduction has been reported in other species. In tomato, overexpression of _SIARF2_ leads to floral organ senescence [32]. Another study claimed that SIARF6 and SIARF8 downregulated by MicroRNA167 may lead to abnormal flower development and female sterility in tomato [14]. In addition to this, [PERSON] et al. [33] found that SIARF1, SIARF9, SIARF11, SIARF15, and SIARF16 were highly expressed during flowering, suggesting that these genes may be associated with flower development in tomato. [PERSON] et al. [34] found that GrARP9 in cotton influences reproductive stages through its involvement in flower development and postulated a function consistent with that of SIARF9 in tomato. Both FvARF6 and FvARF8 are highly expressed early in strawberry fruit formation, and they may be important for flowering and other reproduction of strawberries [13].