Summary Fleshy fruits are classically divided into climacteric and nonclimacteric types. It has long been thought that the ripening of climacteric and nonclimacteric fruits is regulated by ethylene and abscisic acid (ABA), respectively. Here, we report that sucrose functions as a signal in the ripening of strawberry (Fragaria × ananassa), a nonclimacteric fruit. Pharmacological experiments, as well as gain‐ and loss‐of‐function studies, were performed to demonstrate the critical role of sucrose in the regulation of fruit ripening. Fruit growth and development were closely correlated with a change in sucrose content. Exogenous sucrose and its nonmetabolizable analog, turanose, induced ABA accumulation in fruit and accelerated dramatically fruit ripening. A set of sucrose transporters, FaSUT1–7, was identified and characterized, among which FaSUT1 was found to be a major component responsible for sucrose accumulation during fruit development. RNA interference‐induced silencing of FaSUT1 led to a decrease in both sucrose and ABA content, and arrested fruit ripening. By contrast, overexpression of FaSUT1 led to an increase in both sucrose and ABA content, and accelerated fruit ripening. In conclusion, this study demonstrates that sucrose is an important signal in the regulation of strawberry fruit ripening.

Apple leaf spot caused by the f. sp (ALT1) fungus is one of the most devastating diseases of apple ( × ). We identified a hairpin RNA () named that produces small RNAs and is induced by ALT1 infection in 'Golden Delicious' apple. produces mdm-siR277-1 and mdm-siR277-2, which target five resistance () genes that are expressed at high levels in resistant apple variety 'Hanfu' and at low levels in susceptible variety 'Golden Delicious' following ALT1 infection. was strongly induced in 'Golden Delicious' but not 'Hanfu' following ALT1 inoculation. promoter activity was much stronger in inoculated 'Golden Delicious' versus 'Hanfu'. We identified a single-nucleotide polymorphism (SNP) in the promoter region between 'Golden Delicious' () and 'Hanfu' (). The transcription factor MdWHy binds to , but not to Transgenic 'GL-3' apple expressing was more susceptible to ALT1 infection than plants expressing due to induced mdm-siR277 accumulation and reduced expression of the five target genes. We confirmed that the SNP in is associated with leaf spot resistance by crossing. This SNP could be used as a marker to distinguish between apple varieties that are resistant or susceptible to leaf spot.

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DNA methylation is an epigenetic modification essential for gene regulations in plants, but understanding on how it is involved in fruit development, especially in non-climacteric fleshy fruit, is limited. The diploid woodland strawberry (Fragaria vesca) is an important model for non-climacteric fruit crops. In this study, we identified DNA methyltransferase genes and demethylase genes in Fragaria vesca and other angiosperm species. In accordance with previous studies, our phylogenetic analyses of those DNA methylation modifiers support the clustering of those genes into several classes. Our data indicate that whole-genome duplications and tandem duplications contributed to the expansion of those DNA methylation modifiers in angiosperms. We have further demonstrated that some DNA methylase and demethylase genes reach their highest expression levels in strawberry fleshy fruits when turning from white to red, suggesting that DNA methylation might undergo a dramatic change at the onset of fleshy fruit-ripening process. In addition, we have observed that expression of some DNA demethylase genes increases in response to various abiotic stresses including heat, cold, drought and salinity. Collectively, our study indicates a regulatory role of DNA methylation in the turning stage of non-climacteric fleshy fruit and responses to environment stimuli, and would facilitate functional studies of DNA methylation in the growth and development of non-climacteric fruits.