Fruit-Surface Flavonoid Accumulation in Tomato Is Controlled by a SlMYB12-Regulated Transcriptional Network

Abstract

The cuticle covering plants' aerial surfaces is a unique structure that plays a key role in organ development and protection against diverse stress conditions. A detailed analysis of the tomato colorless-peel y mutant was carried out in the framework of studying the outer surface of reproductive organs. The y mutant peel lacks the yellow flavonoid pigment naringenin chalcone, which has been suggested to influence the characteristics and function of the cuticular layer. Large-scale metabolic and transcript profiling revealed broad effects on both primary and secondary metabolism, related mostly to the biosynthesis of phenylpropanoids, particularly flavonoids. These were not restricted to the fruit or to a specific stage of its development and indicated that the y mutant phenotype is due to a mutation in a regulatory gene. Indeed, expression analyses specified three R2R3-MYB–type transcription factors that were significantly down-regulated in the y mutant fruit peel. One of these, SlMYB12, was mapped to the genomic region on tomato chromosome 1 previously shown to harbor the y mutation. Identification of an additional mutant allele that co-segregates with the colorless-peel trait, specific down-regulation of SlMYB12 and rescue of the y phenotype by overexpression of SlMYB12 on the mutant background, confirmed that a lesion in this regulator underlies the y phenotype. Hence, this work provides novel insight to the study of fleshy fruit cuticular structure and paves the way for the elucidation of the regulatory network that controls flavonoid accumulation in tomato fruit cuticle.

High-resolution metabolic mapping of cell types in plant roots

“…When available, metabolites were identified using standard compounds by comparison of their retention times, UV spectra, and MS/MS fragments. In case the corresponding standards were not available, compounds were putatively identified as previously described (14).…”

“…In the current study, we modified the established method for FACS-based, GFP-marked cell isolation from Arabidopsis roots of specific root cell types (12) to carry out metabolomics analysis using high-resolution MS (13,14). Cell extracts were processed and analyzed by means of ultraperformance liquid chromatography (UPLC) coupled to a quadrupole TOF (qTOF) MS detector.…”

“…For the core experiment, we used four biological replicates of WEREWOLF (WER/epidermis) and SCARECROW (SCR/endodermis) and three biological replicates of PET111 (columella), CORTEX, and WOODEN LEG (WOL; stele). The metabolic profiles obtained were analyzed using the XCMS peak picking and alignment software (14,16,17) and a metabolomics data quality control (QC) procedure developed by Brodsky et al (18) and implanted by Rogachev and Aharoni (19). Briefly, the mass signals obtained were clustered (for grouping those masses associated with the same metabolite; SI Methods) and filtered from nonplant origin masses (in comparison to blank samples), and metabolites of interest were putatively identified.…”

Reconstruction of Arabidopsis metabolic network models accounting for subcellular compartmentalization and tissue-specificity

“…Apart from dry seeds (50 mg), 100 mg of each tissue were collected in three biological replicates, according to Baerenfaller et al (26). Isoprenoid extraction and analysis was performed using HPLC coupled to photodiode array, detector, as previously described (44).…”

Analyses of Tomato Fruit Brightness Mutants Uncover Both Cutin-Deficient and Cutin-Abundant Mutants and a New Hypomorphic Allele of GDSL Lipase

“…The thick and easy-to-isolate peel from tomato has long been used for studying the biomechanical properties of plant cuticle (Domínguez et al, 2011). In recent years, the increased availability of tomato genomic resources, including saturated genetic linkage maps, markers, and very recently the tomato genomic sequence (Tomato Genome Consortium, 2012), offered unprecedented possibilities for exploiting tomato as a model for studying plant cuticle (Hovav et al, 2007;Adato et al, 2009;Isaacson et al, 2009;Girard et al, 2012;Yeats et al, 2012b;Shi et al, 2013). To fully explore the relationships between cuticle composition and cuticle properties and to discover new genes and functions, new sources of genetic variability affecting tomato genes involved in wax, cutin, and suberin synthesis and regulation are required.…”