The PcERF5 promotes anthocyanin biosynthesis in red-fleshed pear(Pyrus communis)through both activating and interacting with PcMYB transcription factors

As there is a strong interest in red-skinned pears,the molecular mechanism of anthocyanin regulation in red-skinned pears has been widely investigated;however,little is known about the molecular mechanism of anthocyanin regulation in red-fleshed pears due to limited availability of such germplasm,primarily found in European pears(Pyrus communis).In this study,based on transcriptomic analysis in red-fleshed and white-fleshed pears,we identified an ethylene response factor(ERF)from P.communis,PcERF5,of which expression level in fruit flesh was significantly correlated with anthocyanin content.We then verified the function of PcERF5 in regulating anthocyanin accumulation by genetic transformation in both pear skin and apple calli.PcERF5 regulated anthocyanin biosynthesis by different regulatory pathways.On the one hand,PcERF5 can activate the transcription of flavonoid biosynthetic genes(PcDFR,PcANS and PcUFGT)and two key transcription factors encoding genes PcMYB10 and PcMYB114.On the other hand,PcERF5 interacted with PcMYB10 to form the ERF5-MYB10 protein complex that enhanced the transcriptional activation of PcERF5 on its target genes.Our results suggested that PcERF5 functioned as a transcriptional activator in regulating anthocyanin biosynthesis,which provides new insights into the regulatory mechanism of anthocyanin biosynthesis.This new knowledge will provide guidance for molecular breeding of red-fleshed pear.

Unraveling a genetic roadmap for improved taste in the domesticated apple

Although taste is an important aspect of fruit quality, an understanding of its genetic control remains elusive in apple and other fruit crops. In this study, we conducted genomic sequence analysis of 497 Malus accessions and revealed erosion of genetic diversity caused by apple breeding and possible independent domestication events of dessert and cider apples. Signatures of selection for fruit acidity and size, but not for fruit sugar content, were detected during the processes of both domestication and improvement. Furthermore, we found that single mutations in major genes affecting fruit taste, including Ma1, MdTDT, and MdSOT2, dramatically decrease malate, citrate, and sorbitol accumulation, respectively, and correspond to important domestication events. Interestingly, Ma1 was identified to have pleiotropic effects on both organic acid content and sugar:acid ratio, suggesting that it plays a vital role in determining fruit taste. Fruit taste is unlikely to have been negatively affected by linkage drag associated with selection for larger fruit that resulted from the pyramiding of multiple genes with minor effects on fruit size. Collectively, our study provides new insights into the genetic basis of fruit quality and its evolutionary roadmap during apple domestication, pinpointing several candidate genes for genetic manipulation of fruit taste in apple.