The SlSHN2 transcription factor contributes to cuticle formation and epidermal patterning in tomato fruit

Abstract

Tomato (Solanum lycopersicum) is an established model for studying plant cuticle because of its thick cuticle covering and embedding the epidermal cells of the fruit. In this study, we screened an EMS mutant collection of the miniature tomato cultivar Micro-Tom for fruit cracking mutants and found a mutant displaying a glossy fruit phenotype. By using an established mapping-by-sequencing strategy, we identified the causal mutation in the SlSHN2 transcription factor that is specifically expressed in outer epidermis of growing fruit. The point mutation in the shn2 mutant introduces a K to N amino acid change in the highly conserved ‘mm’ domain of SHN proteins. The cuticle from shn2 fruit showed a ~ fivefold reduction in cutin while abundance and composition of waxes were barely affected. In addition to alterations in cuticle thickness and properties, epidermal patterning and polysaccharide composition of the cuticle were changed. RNAseq analysis further highlighted the altered expression of hundreds of genes in the fruit exocarp of shn2, including genes associated with cuticle and cell wall formation, hormone signaling and response, and transcriptional regulation. In conclusion, we showed that a point mutation in the transcriptional regulator SlSHN2 causes major changes in fruit cuticle formation and its coordination with epidermal patterning.

Microscopic and metabolic investigations disclose the factors that lead to skin cracking in chili-type pepper fruit varieties

“…3F ). Only recently, the tomato SHN2 gene was shown to participate in the synthesis of the cuticle along with epidermal patterning formation in the fruit skin [ 48 ].…”

Cuticle deposition ceases during strawberry fruit development

“…They regulate CM formation in Arabidopsis thaliana and Solanum lycopersicum , AtSHN1 governs wax and cutin synthesis in A . thaliana [ 35 ], SlSHN2 [ 36 ] and SlSHN3 [ 37 ] that in S . lycopersicum .…”

Dissection of mRNA ac4C acetylation modifications in AC and Nr fruits: insights into the regulation of fruit ripening by ethylene

“…The tomato ripening process involves major physiological and biochemical changes, such as pigments accumulation, chlorophyll degradation leading to color change, cell wall depolymerization causing fruit softening, the accumulation of sugars and acids contributing to unique flavor, and the biosynthesis of characteristic nutrients (Giovannoni et al 2017 ; Wang and Seymour 2022 ; Zhu et al 2022 ). These processes are tightly regulated through the modulation of expression of many genes (Bres et al 2022 ; Wang et al 2022 ). The molecular mechanism of ripening depends on the coordination of transcription factors (Gapper et al 2013 ; Chen et al 2020 ), plant hormones (Kumar et al 2014 ; Fenn and Giovannoni 2021 ; Fu et al 2022 ), DNA methylation (Tang et al 2020 ; Yao et al 2022 ), and histone modifications (Lü et al 2018 ).…”