Auxin plays essential roles in plant normal growth and development. The auxin signaling pathway relies on the auxin gradient within tissues and cells, which is facilitated by both local auxin biosynthesis and polar auxin transport (PAT). The TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS (TAA)/YUCCA (YUC) pathway is the most important and well-characterized pathway that plants deploy to produce auxin. YUCs function as flavin-containing monooxygenases (FMO) catalyzing the rate-limiting irreversible oxidative decarboxylation of indole-3-pyruvate acid (IPyA) to form indole-3-acetic acid (IAA). The spatiotemporal dynamic expression of different YUC gene members finely tunes the local auxin biosynthesis in plants, which contributes to plant development as well as environmental responses. In this review, the recent advances in the identification, evolution, molecular structures, and functions in plant development and stress response regarding the YUC gene family are addressed.

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