## 8 Challenges and Outlooks  
Currently, increasingly more studies have found evidence of ARF involvement in the regulation of plant growth and development, but the exploration of deeper molecular mechanisms and the construction of regulatory networks are not well developed. One of the major challenges for the future is to define the specific functions of each individual ARF gene during plant growth and development. The auxin signal transduction pathway mediated by ARFs is very complex, and we still need to further systematically study the target genes of ARFS in the auxin pathway, such as SAUR, GH3, and AUX/IAA, which will help us to have a more comprehensive and deeper understanding of the role of ARFS in plant growth, development, and environmental adaptation. As early as 2004, [PERSON] et al. [63] suggested that in Arabidopsis ARF8 may control free IAA levels in a negative feedback manner by regulating GH3 gene expression, which may be important for maintaining auxin homeostasis. Advancing the study of negative feedback mechanisms will facilitate our comprehensive understanding of the auxin signal transduction pathway. In addition, further research on the deterministic interactions between transcription factors and transcription factors, as well as between transcription factors and genes, is needed. For example, some researchers found significant changes in the expression of ARF genes in banana and grape, respectively, during fruit development and ripening [64]. However, we are not aware of any studies related to the involvement of ARFs in the fruit development and ripening mechanisms of these two fruits. Overexpression, RNAi, and genome-editing methods such as CRISPR-Cas9 should be applied more widely to investigate the function and mechanism of ARFs. In addition, the function of ARFs in some species is still in the initial stage, and only a few relevant studies have performed identification and differential expression analysis of ARF genes, such as litchi [15]. The potential role of ARFs in these species needs to be further explored and verified. After the ARFs genes have been identified, further work should focus on identifying the protein partners that bind to them and the genes that they directly target to regulate. It is generally accepted that ARF family proteins and Aux/IAA family proteins are involved in the auxin signal transduction pathways in a mutually binding manner. In reality, however, the exact interaction between the two that actually occurs in plants is not known, and the specific effects of this interaction are not well understood. Many studies have been able to demonstrate theoretical interactions between ARF transcription factors and Aux/IAA family proteins, or with other proteins, through methods such as yeast two-hybrid crosses, but there is often a lack of more robust evidence to confirm whether such interactions actually occur in plants. We speculate that the binding between ARF and Aux/IAA should be dynamic and not static, exhibiting different levels of interaction in different environments, or even only under certain conditions (e.g., auxin concentrations below a threshold). Considering that the interaction between Aux/IAA protein and ARFs is widespread, a more complete research plan should be to simultaneously analyze the effects of Aux/IAA proteins interacting with ARFs when studying the regulation of ARFs on plant growth and development. In addition, numerous studies have shown that an ARF protein can interact with multiple Aux/IAAs and vice versa. [PERSON] [44] and [PERSON] [65] demonstrated the interaction between IAA9 and ARF7/ARF5 by yeast two-hybrid system (Y2H) experiments, respectively. A study has shown that ARFs that act as activators (e.g., PeARF14, SIARF6A) have a higher affinity for Aux/IAAs interactions compared to ARFs that act as repressors (e.g., PeARF24, SIARF2A). The phenomenon seems to be conserved in some species (e.g., tomato, Arabidopsis, and rice), but it is unknown as to whether this is the case across the plant kingdom [66; 67; 68].