Genome-wide association studies in apple reveal loci of large effect controlling apple polyphenols

Apples are a nutritious food source with significant amounts of polyphenols that contribute to human health and wellbeing,primarily as dietary antioxidants.Although numerous pre-and post-harvest factors can affect the composition of polyphenols in apples,genetics is presumed to play a major role because polyphenol concentration varies dramatically among apple cultivars.Here we investigated the genetic architecture of apple polyphenols by combining high performance liquid chromatography(HPLC)data with~100,000 single nucleotide polymorphisms(SNPs)from two diverse apple populations.We found that polyphenols can vary in concentration by up to two orders of magnitude across cultivars,and that this dramatic variation was often predictable using genetic markers and frequently controlled by a small number of large effect genetic loci.Using GWAS,we identified candidate genes for the production of quercitrin,epicatechin,catechin,chlorogenic acid,4-O-caffeoylquinic acid and procyanidins B1,B2,and C1.Our observation that a relatively simple genetic architecture underlies the dramatic variation of key polyphenols in apples suggests that breeders may be able to improve the nutritional value of apples through markerassisted breeding or gene editing.

Proteome changes in banana fruit peel tissue in response to ethylene and high-temperature treatments

Banana(Musa AAA group)is one of the most consumed fruits in the world due to its flavor and nutritional value.As a typical climacteric fruit,banana responds to ethylene treatment,which induces rapid changes of color,flavor(aroma and taste),sweetness and nutritional composition.It has also been reported that ripening bananas at temperatures above 24℃ inhibits chlorophyll breakdown and color formation but increases the rate of senescence.To gain fundamental knowledge about the effects of high temperature and ethylene on banana ripening,a quantitative proteomic study employing multiplex peptide stable isotope dimethyl labeling was conducted.In this study,green(immature)untreated banana fruit were subjected to treatment with 10μL L^(−1) of ethylene for 24 h.After ethylene treatment,treated and untreated fruit were stored at 20 or 30℃ for 24 h.Fruit peel tissues were then sampled after 0 and 1 day of storage,and peel color and chlorophyll fluorescence were evaluated.Quantitative proteomic analysis was conducted on the fruit peels after 1 day of storage.In total,413 common proteins were identified and quantified from two biological replicates.Among these proteins,91 changed significantly in response to ethylene and high-temperature treatments.Cluster analysis on these 91 proteins identified 7 groups of changed proteins.Ethylene treatment and storage at 20℃ induced 40 proteins that are correlated with pathogen resistance,cell wall metabolism,ethylene biosynthesis,allergens and ribosomal proteins,and it repressed 36 proteins that are associated with fatty acid and lipid metabolism,redox–oxidative responses,and protein biosynthesis and modification.Ethylene treatment and storage at 30℃ induced 32 proteins,which were mainly similar to those in group 1 but also included 8 proteins in group 3(identified as chitinase,cinnamyl alcohol dehydrogenase 1,cysteine synthase,villin-2,leucine-transfer RNA ligase,CP47 protein and calmodulin)and repressed 43 proteins in 4 groups(groups 4–7),of which 6 were associated with photosynthesis II oxygen-evolving protein,the photosynthesis I reaction center,sugar metabolism,the redox–oxidative system and fatty acid metabolism.Differences in the response to ethylene and holding temperature at 30℃ were also revealed and have been discussed.The identities and quantities of the proteins found were linked with quality changes.This study demonstrates that ethylene and high temperature influence banana fruit ripening and senescence at the proteomic level and reveals the mechanisms by which high temperature accelerates banana fruit ripening.