Andrés Borges-Pérez

Cloning and Biochemical Characterization of ToFZY, a Tomato Gene Encoding a Flavin Monooxygenase Involved in a Tryptophan-dependent Auxin Biosynthesis Pathway

Indole-3-acetic acid (IAA), the main endogenous auxin, has been known for decades to be a key regulator for plant growth and development. Multiple routes have been proposed for IAA biosynthesis but physiologic roles or relevance of the different routes are still unclear. Recently, four members of the Arabidopsis thaliana YUC gene family have been implicated in an additional requirement of IAA involved in floral organ and vascular tissue formation. The loss-of-function yuc1yuc4 double mutants in Arabidopsis displayed phenotypes similar to the previously described loss-of-function floozy mutants in petunia (fzy). Moreover, it has been demonstrated that YUC1 encodes a flavin monooxygenase (FMO) that catalyzes a rate-limiting step of a tryptophan-dependent auxin biosynthesis pathway: the conversion of tryptamine to N-hydroxyl-tryptamine. Here we report on the genetic study of ToFZY, the putative tomato ortholog of YUC4 and FZY, including gene and cDNA sequence comparison and a preliminary expression analysis. In addition, we describe a novel conserved amino acid motif that may be considered a hallmark potentially useful for the identification of new YUC-like FMOs. We also demonstrate that ToFZY encodes a protein with the same enzymatic activity as YUC1. Finally, we provide evidence suggesting that the ToFZY gene belongs to a multigenic family whose members may exhibit a temporal and spatial specialization similar to that described in A. thaliana.

Gene structure and spatiotemporal expression profile of tomato genes encoding YUCCA-like flavin monooxygenases: the ToFZY gene family.

The flavin monooxygenases (FMO) encoded by plant YUCCA genes are thought to catalyze a rate-limiting step in the tryptamine pathway for indole-3-acetic acid biosynthesis. Recent experiments with different plant models have indicate that YUCCA genes play essential roles in growth and development through their contribution to the local pool of free auxin. In this study we have characterized five new genes that encode YUCCA-like FMOs in the tomato genome (ToFZY2 to ToFZY6), including gene structure, conserved motifs and phylogenetic analyses. As a first step towards clarifying the individual functions of ToFZY genes, we have used quantitative real-time RT-PCR to conduct a systematic comparison of the steady-state mRNA levels of 6 ToFZY genes, in 33 samples representing major organs and the entire tomato life cycle. We followed an absolute quantification strategy which allowed us to cross-compare transcript levels among different ToFZY genes in a given spatiotemporal coordinate. Our results indicate that expression of ToFZY genes is temporally and spatially regulated, and that the distinctive expression pattern of each ToFZY gene partially overlaps with other members of the multigenic family. We compare our data with previous results in other plant species and make some predictions about the role of tryptamine pathway in tomato growth and development.