Auxin biosynthesis in plants is a complex process involving multiple pathways, with indole-3-acetic acid (IAA) being the primary auxin. Recent studies have identified key genes in tryptophan-dependent auxin biosynthesis pathways, revealing that local auxin biosynthesis is essential for various developmental processes, including gametogenesis, embryogenesis, seedling growth, vascular patterning, and flower development. The YUCCA (YUC) family of flavin monooxygenases and the TAA1 gene are central to auxin biosynthesis, with YUC genes playing a critical role in local auxin production. The TAA1 gene is involved in converting tryptophan to indole-3-pyruvate (IPA), which is then converted to IAA. The YUC pathway is highly conserved across plant species, and its disruption leads to developmental defects. Auxin biosynthesis is also regulated by environmental and developmental signals, with genes such as YUC and TAA1 showing spatial and temporal expression patterns. Understanding auxin biosynthesis provides new tools for studying plant development and has implications for manipulating auxin levels in plants. The identification of key genes and pathways in auxin biosynthesis has advanced our understanding of how auxin regulates plant development, although the complete pathway remains elusive. Future research aims to clarify the relationships between different auxin biosynthesis pathways and their roles in plant growth and development.Auxin biosynthesis in plants is a complex process involving multiple pathways, with indole-3-acetic acid (IAA) being the primary auxin. Recent studies have identified key genes in tryptophan-dependent auxin biosynthesis pathways, revealing that local auxin biosynthesis is essential for various developmental processes, including gametogenesis, embryogenesis, seedling growth, vascular patterning, and flower development. The YUCCA (YUC) family of flavin monooxygenases and the TAA1 gene are central to auxin biosynthesis, with YUC genes playing a critical role in local auxin production. The TAA1 gene is involved in converting tryptophan to indole-3-pyruvate (IPA), which is then converted to IAA. The YUC pathway is highly conserved across plant species, and its disruption leads to developmental defects. Auxin biosynthesis is also regulated by environmental and developmental signals, with genes such as YUC and TAA1 showing spatial and temporal expression patterns. Understanding auxin biosynthesis provides new tools for studying plant development and has implications for manipulating auxin levels in plants. The identification of key genes and pathways in auxin biosynthesis has advanced our understanding of how auxin regulates plant development, although the complete pathway remains elusive. Future research aims to clarify the relationships between different auxin biosynthesis pathways and their roles in plant growth and development.