The tomato SlSHINE3 transcription factor regulates fruit cuticle formation and epidermal patterning

Abstract

SummaryFleshy tomato fruit typically lacks stomata; therefore, a proper cuticle is particularly vital for fruit development and interaction with the surroundings. Here, we characterized the tomato SlSHINE3 (SlSHN3) transcription factor to extend our limited knowledge regarding the regulation of cuticle formation in fleshy fruits.We created SlSHN3 overexpressing and silenced plants, and used them for detailed analysis of cuticular lipid compositions, phenotypic characterization, and the study on the mode of SlSHN3 action.Heterologous expression of SlSHN3 in Arabidopsis phenocopied overexpression of the Arabidopsis SHNs. Silencing of SlSHN3 results in profound morphological alterations of the fruit epidermis and significant reduction in cuticular lipids. We demonstrated that SlSHN3 activity is mediated by control of genes associated with cutin metabolism and epidermal cell patterning. As with SlSHN3 RNAi lines, mutation in the SlSHN3 target gene, SlCYP86A69, resulted in severe cutin deficiency and altered fruit surface architecture. In vitro activity assays demonstrated that SlCYP86A69 possesses NADPH-dependent x-hydroxylation activity, particularly of C18:1 fatty acid to the 18-hydroxyoleic acid cutin monomer.This study provided insights into transcriptional mechanisms mediating fleshy fruit cuticle formation and highlighted the link between cutin metabolism and the process of fruit epidermal cell patterning.

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

“…fruit growth, visual aspect, cracking, water loss, resistance to pathogens, and postharvest shelf-life) are highly dependent on fruit cuticle (Bargel and Neinhuis, 2005;Saladié et al, 2007;Matas et al, 2009;Domínguez et al, 2011;Parsons et al, 2012). An increasing number of studies highlight the possibilities offered by tomato for analyzing cuticle architecture, mechanical properties, and permeability (López-Casado et al, 2007;Saladié et al, 2007;MintzOron et al, 2008;Buda et al, 2009;Isaacson et al, 2009;Wang et al, 2011) and for discovering genes contributing to cuticle synthesis and regulation (Hovav et al, 2007;Mintz-Oron et al, 2008;Girard et al, 2012;Nadakuduti et al, 2012;Yeats et al, 2012b;Shi et al, 2013). Nevertheless, to further our understanding of the relationships between cuticle composition and architecture and cuticle properties and performance in plants, new tomato cuticle mutants are highly needed (Domínguez et al, 2011).…”

“…Less straightforward than TILLING, this approach relies first on the phenotypic characterization of the mutant trait and then on the identification of the mutation through map-based cloning, combined (or not) with the candidate gene approach or, more recently, through whole-genome sequencing (Abe et al, 2012;Just et al, 2013). Using this strategy, new cuticle-related genes involved in cuticle regulation (the cd2 HD-ZIP IV mutant; Isaacson et al, 2009), cutin monomer biosynthesis (the cyp86A9 mutant; Shi et al, 2013), and cutin polymerization (the cutin synthase mutant; Yeats et al, 2012b) were recently uncovered in tomato EMS mutant collections. However, when considering the large number of candidate genes involved in the regulation, synthesis, and transport processes necessary for cuticle formation (Matas et al, 2011;Yeats and Rose, 2013), very few tomato cuticle mutants have been described to date (Kimbara et al, 2012;Nadakuduti et al, 2012;Shi et al, 2013).…”

“…fruit glossier or duller than the wild-type control]). Strong fruit cuticle/ color mutants, such as the slcyp86a9 cuticle synthesis mutant recently identified from the same 'Micro-Tom' mutant collection (Shi et al, 2013), were excluded from the analysis. As shown in Figure 1, the first query using these criteria resulted in the identification of 274 mutant families.…”

“…Several of their downstream targets involved in cutin synthesis, modification, and assembly, as well as in cell wall formation and structure and in epidermal cell patterning (Shi et al, 2013), have been identified. Other transcription factors of the MYB protein family, Homeodomain-leucine-zipper (HD-ZIP) IV family, and WW domain protein were shown to control cuticle formation, some of which and were suggested to take part in a regulatory network controlling epidermal cell patterning (Yeats and Rose, 2013).…”

“…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.…”