Quantitative trait loci influencing pentacyclic triterpene composition in apple fruit peel

The chemical composition of pentacyclic triterpenes was analysed using a ‘Royal Gala’ x ‘Granny Smith’ segregating population in 2013 and 2015, using apple peels extracted from mature fruit at harvest and after 12 weeks of cold storage. In 2013, 20 compound isoforms from nine unique compound classes were measured for both treatments. In 2015, 20 and 17 compound isoforms from eight unique compound classes were measured at harvest and after cold storage, respectively. In total, 68 quantitative trait loci (QTLs) were detected on 13 linkage groups (LG). Thirty two and 36 QTLs were detected for compounds measured at harvest and after cold storage, respectively. The apple chromosomes with the most QTLs were LG3, LG5, LG9 and LG17. The largest effect QTL was for trihydroxy-urs-12-ene-28-oic acid, located on LG5; this was measured in 2015 after storage, and was inherited from the ‘Royal Gala’ parent (24.9% of the phenotypic variation explained)

An R2R3 MYB transcription factor associated with regulation of the anthocyanin biosynthetic pathway in Rosaceae

<p>Abstract</p> <p>Background</p> <p>The control of plant anthocyanin accumulation is via transcriptional regulation of the genes encoding the biosynthetic enzymes. A key activator appears to be an R2R3 MYB transcription factor. In apple fruit, skin anthocyanin levels are controlled by a gene called <it>MYBA </it>or <it>MYB1</it>, while the gene determining fruit flesh and foliage anthocyanin has been termed <it>MYB10</it>. In order to further understand tissue-specific anthocyanin regulation we have isolated orthologous <it>MYB </it>genes from all the commercially important rosaceous species.</p> <p>Results</p> <p>We use gene specific primers to show that the three MYB activators of apple anthocyanin (<it>MYB10/MYB1/MYBA) </it>are likely alleles of each other. MYB transcription factors, with high sequence identity to the apple gene were isolated from across the rosaceous family (e.g. apples, pears, plums, cherries, peaches, raspberries, rose, strawberry). Key identifying amino acid residues were found in both the DNA-binding and C-terminal domains of these MYBs. The expression of these <it>MYB10 </it>genes correlates with fruit and flower anthocyanin levels. Their function was tested in tobacco and strawberry. In tobacco, these MYBs were shown to induce the anthocyanin pathway when co-expressed with bHLHs, while over-expression of strawberry and apple genes in the crop of origin elevates anthocyanins.</p> <p>Conclusions</p> <p>This family-wide study of rosaceous R2R3 MYBs provides insight into the evolution of this plant trait. It has implications for the development of new coloured fruit and flowers, as well as aiding the understanding of temporal-spatial colour change.</p

QTL and candidate gene mapping for polyphenolic composition in apple fruit

<p>Abstract</p> <p>Background</p> <p>The polyphenolic products of the phenylpropanoid pathway, including proanthocyanidins, anthocyanins and flavonols, possess antioxidant properties that may provide health benefits. To investigate the genetic architecture of control of their biosynthesis in apple fruit, various polyphenolic compounds were quantified in progeny from a 'Royal Gala' × 'Braeburn' apple population segregating for antioxidant content, using ultra high performance liquid chromatography of extracts derived from fruit cortex and skin.</p> <p>Results</p> <p>Construction of genetic maps for 'Royal Gala' and 'Braeburn' enabled detection of 79 quantitative trait loci (QTL) for content of 17 fruit polyphenolic compounds. Seven QTL clusters were stable across two years of harvest and included QTLs for content of flavanols, flavonols, anthocyanins and hydroxycinnamic acids. Alignment of the parental genetic maps with the apple whole genome sequence <it>in silico </it>enabled screening for co-segregation with the QTLs of a range of candidate genes coding for enzymes in the polyphenolic biosynthetic pathway. This co-location was confirmed by genetic mapping of markers derived from the gene sequences. <it>Leucoanthocyanidin reductase </it>(<it>LAR1</it>) co-located with a QTL cluster for the fruit flavanols catechin, epicatechin, procyanidin dimer and five unknown procyanidin oligomers identified near the top of linkage group (LG) 16, while <it>hydroxy cinnamate/quinate transferase </it>(<it>HCT</it>/<it>HQT</it>) co-located with a QTL for chlorogenic acid concentration mapping near the bottom of LG 17.</p> <p>Conclusion</p> <p>We conclude that <it>LAR1 </it>and <it>HCT</it>/<it>HQT </it>are likely to influence the concentration of these compounds in apple fruit and provide useful allele-specific markers for marker assisted selection of trees bearing fruit with healthy attributes.</p

Lactic acid bacteria convert glucosinolates to nitriles efficiently yet differently from enterobacteriaceae

Glucosinolates from the genus Brassica can be converted into bioactive compounds known to induce phase II enzymes, which may decrease the risk of cancers. Conversion via hydrolysis is usually by the brassica enzyme myrosinase, which can be inactivated by cooking or storage. We examined the potential of three beneficial bacteria, Lactobacillus plantarum KW30, Lactococcus lactis subsp. lactis KF147, and Escherichia con Nissle 1917, and known myrosinase-producer Enterobacter cloacae to catalyze the conversion of glucosinolates in broccoli extract. Enterobacteriaceae consumed on average 65% glucoiberin and 78% glucoraphanin, transforming them into glucoiberverin and glucoerucin, respectively, and small amounts of iberverin nitrile and erucin nitrile. The lactic acid bacteria did not accumulate reduced glucosinolates, consuming all at 30-33% and transforming these into iberverin nitrile, erucin nitrile, sulforaphane nitrile, and further unidentified metabolites. Adding beneficial bacteria to a glucosinolate-rich diet may increase glucosinolate transformation, thereby increasing host exposure to bioactives

Flavonoid biosynthesis is differentially altered in detached and attached ripening bilberries in response to spectral light quality

Light spectral quality is known to affect flavonoid biosynthesis during fruit ripening. However, the response of fruits to different light conditions, when ripening autonomously from the parent plant (detached), has been less explored. In this study, we analyzed the effect of light quality on detached and naturally ripening (attached) non-climacteric wild bilberry (Vaccinium myrtillus L.) fruits accumulating high amounts of anthocyanins and flavonols. Our results indicated contrasting responses for the accumulation of phenolic compounds in the berries in response to red and blue light treatments. For detached berries, supplemental blue light resulted in the highest accumulation of anthocyanins, while naturally ripening berries had elevated accumulation under supplemental red light treatment. Both red and blue supplemental light increased the expression levels of all the major structural genes of the flavonoid pathway during ripening. Notably, the key regulatory gene of anthocyanin biosynthesis, VmMYBA1, was found to express fivefold higher under blue light treatment in the detached berries compared to the control. The red light treatment of naturally ripening berries selectively increased the delphinidin branch of anthocyanins, whereas in detached berries, blue light increased other anthocyanin classes along with delphinidins. In addition, red and far-red light had a positive influence on the accumulation of flavonols, especially quercetin and myricetin glycoside derivatives, in both ripening conditions. Our results of differential light effects on attached and detached berries, which lacks signaling from the mother plant, provide new insights in understanding the light-mediated regulatory mechanisms in non-climacteric fruit ripening

Biochemical responses of suspension-cultured sugarcane cells to an elicitor derived from the root pathogen Pachymetra chaunorhiza

The fungus Pachymetra chaunorhiza Croft and Dick causes a root rot in sugarcane (Saccharum interspecific hybrid). Suspension-cultured sugarcane cells prepared from cultivars Q114 (P. chaunorhiza resistant) and Q90 (P. chaunorhiza susceptible) were inoculated with a heat-derived elicitor preparation from P. chaunorhiza and the cellular responses monitored by measuring phenylalanine ammonia-lyase (PAL) and perexidase (POD) activity and the production of additional phenolic compounds. Introduction of the P. chaunorhiza elicitor induced marked changes in the biochemistry of both sugarcane cell lines. Both cell lines produced additional phenolic compounds not present in untreated cells and different compounds were produced by each cell line. Induced enzyme activities also differed between the cell lines with Q90 (susceptible) showing a large and transitory increase in PAL activity that was far greater than that observed for Q114 (resistant). POD activity increased more in Q114 than in Q90, although the differences between the resistant and susceptible cell lines were not as great as for PAL