Tree Genetics and Molecular Breeding 2024, Vol.14, No.3, 155-165 http://genbreedpublisher.com/index.php/tgmb 162 modulating plant growth. In grapevine, the application of an auxin inhibitor reduced cell number and mesocarp diameter, highlighting the potential of such compounds in controlling fruit development and branching (Gomes and Scortecci, 2021). These chemical approaches provide a flexible and non-genetic means to influence auxin signaling and can be integrated with genetic engineering techniques for more comprehensive control over plant architecture. 7.3 Potential for crop improvement and yield enhancement Manipulating auxin signaling holds significant promise for crop improvement and yield enhancement. By optimizing branching patterns, it is possible to increase the number of fruit-bearing branches, thereby boosting overall fruit production. The interplay between auxin and other phytohormones, such as gibberellic acid (GA), further underscores the potential for integrated hormone management to enhance crop yields (He and Yamamuro, 2022). Recent studies have demonstrated that the interaction between ARF/IAA and DELLA proteins, which are involved in both auxin and GA signaling pathways, plays a crucial role in fruit development and can be targeted for crop improvement (He and Yamamuro, 2022). Moreover, the crosstalk between auxin and sugar signaling pathways has been shown to regulate various agriculturally important traits, suggesting that a holistic approach to hormone management could lead to significant advancements in crop productivity (Mishra et al., 2021). Overall, the strategic manipulation of auxin signaling, through both genetic and chemical means, offers a promising avenue for enhancing branching, improving fruit quality, and increasing crop yields. 8 Challenges and Future Directions 8.1 Limitations in current research on auxin signaling Despite significant advancements in understanding auxin signaling, several limitations persist. One major challenge is the complexity of auxin signal transduction pathways, which involve multiple components and interactions that are not yet fully elucidated. For instance, while the canonical TIR1/AFB-mediated transcriptional pathway is well-studied, the non-canonical pathways, such as those mediated by TRANSMEMBRANE KINASEs (TMKs), require further exploration to understand their roles in plant growth and development (Gallei et al. 2019; Yu et al. 2022). Additionally, the feedback inhibition mechanisms that prevent the over-amplification of auxin signals are not completely understood, posing a challenge for manipulating these pathways for agricultural benefits (Yu et al. 2022). Another limitation is the species-specific nature of auxin signaling components. For example, while ARF genes have been extensively studied in model plants like Arabidopsis, their roles in other species, including fruit trees, are less well-characterized (Li et al., 2022). This gap in knowledge hinders the application of findings from model plants to economically important fruit trees. Moreover, the interaction between auxin and other phytohormones, such as gibberellic acid (GA), in regulating fruit development is complex and not fully understood, necessitating further research (He and Yamamuro, 2022). 8.2 Emerging technologies and their potential impact Emerging technologies offer promising avenues to overcome current limitations in auxin signaling research. Advanced genomic and transcriptomic techniques, such as whole-genome sequencing and RNA sequencing, have already facilitated the identification of numerous ARF genes across different species, including fruit trees (Li et al., 2022; Liang et al., 2022). These technologies enable a more comprehensive understanding of the genetic basis of auxin signaling and its role in plant development. CRISPR/Cas9 genome editing technology holds significant potential for functional studies of auxin signaling components. By enabling precise modifications of specific genes, CRISPR/Cas9 can help elucidate the roles of less-studied auxin signaling components and their interactions with other phytohormones (Xu et al., 2019). Additionally, bioinformatics tools and integrative analyses, such as those used to study the regulatory networks in longan, can provide insights into the complex interactions between auxin signaling and other pathways (Liang et al., 2022).
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