Precise Regulation of the TAA1/TAR-YUCCA Auxin Biosynthesis Pathway in Plants

Abstract

The indole-3-pyruvic acid (IPA) pathway is the main auxin biosynthesis pathway in the plant kingdom. Local control of auxin biosynthesis through this pathway regulates plant growth and development and the responses to biotic and abiotic stresses. During the past decades, genetic, physiological, biochemical, and molecular studies have greatly advanced our understanding of tryptophan-dependent auxin biosynthesis. The IPA pathway includes two steps: Trp is converted to IPA by TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS/TRYPTOPHAN AMINOTRANSFERASE RELATED PROTEINs (TAA1/TARs), and then IPA is converted to IAA by the flavin monooxygenases (YUCCAs). The IPA pathway is regulated at multiple levels, including transcriptional and post-transcriptional regulation, protein modification, and feedback regulation, resulting in changes in gene transcription, enzyme activity and protein localization. Ongoing research indicates that tissue-specific DNA methylation and miRNA-directed regulation of transcription factors may also play key roles in the precise regulation of IPA-dependent auxin biosynthesis in plants. This review will mainly summarize the regulatory mechanisms of the IPA pathway and address the many unresolved questions regarding this auxin biosynthesis pathway in plants.

Auxin regulates bulbil initiation by mediating sucrose metabolism in Lilium lancifolium

“…In addition, moderating auxin biosynthesis can regulate lateral organ initiation. The production of auxin primarily relies on tryptophan (TRP)-dependent biosynthetic pathways, where enzymes TAR and YUC are essential [ 42 ]. Studies on moss gametophores through tarac and yuccf mutants showed that inhibiting TAR and YUC genes can increase lateral branching and reduce apical dominance [ 13 ].…”

Identification and evolution analysis of YUCCA genes of Medicago sativa and Medicago truncatula and their expression profiles under abiotic stress

“…Therefore, the stress tolerance of 95-608 should be further compared with other varieties. Studies indicate that miRNA-directed regulation of transcription factors may also play key roles in the precise regulation of IPA-dependent auxin biosynthesis in plants ( Luo and Di, 2023 ). In this study, all MsYUCs contained at least three predicted targets for miRNA, suggesting a miRNA-directed regulation of YUC in M. sativa ( Figure 6C ).…”

Plant Growth Regulation in Cell and Tissue Culture In Vitro

“…In the frame of this pathway, first, Indole-3-pyruvic acid (IPA) was formed by the action of the TAA1 gene, and thereafter, numerous YUCCA genes were converted from IPA to IAA. Recently, the key role of the TAA1 gene and several auxin transporters in the process of the induction of embryos in plants was shown [ 120 , 121 ]. However, auxin itself, auxin “concentration” or level, cannot be used as a marker for any morphogenic processes.…”