Expression Patterns of Genes Involved in Sugar Metabolism and Accumulation during Apple Fruit Development

Both sorbitol and sucrose are imported into apple fruit from leaves. The metabolism of sorbitol and sucrose fuels fruit growth and development, and accumulation of sugars in fruit is central to the edible quality of apple. However, our understanding of the mechanisms controlling sugar metabolism and accumulation in apple remains quite limited. We identified members of various gene families encoding key enzymes or transporters involved in sugar metabolism and accumulation in apple fruit using homology searches and comparison of their expression patterns in different tissues, and analyzed the relationship of their transcripts with enzyme activities and sugar accumulation during fruit development. At the early stage of fruit development, the transcript levels of sorbitol dehydrogenase, cell wall invertase, neutral invertase, sucrose synthase, fructokinase and hexokinase are high, and the resulting high enzyme activities are responsible for the rapid utilization of the imported sorbitol and sucrose for fruit growth, with low levels of sugar accumulation. As the fruit continues to grow due to cell expansion, the transcript levels and activities of these enzymes are down-regulated, with concomitant accumulation of fructose and elevated transcript levels of tonoplast monosaccharide transporters (TMTs), MdTMT1 and MdTMT2; the excess carbon is converted into starch. At the late stage of fruit development, sucrose accumulation is enhanced, consistent with the elevated expression of sucrose-phosphate synthase (SPS), MdSPS5 and MdSPS6, and an increase in its total activity. Our data indicate that sugar metabolism and accumulation in apple fruit is developmentally regulated. This represents a comprehensive analysis of the genes involved in sugar metabolism and accumulation in apple, which will serve as a platform for further studies on the functions of these genes and subsequent manipulation of sugar metabolism and fruit quality traits related to carbohydrates

Increasing the source/sink ratio in Vitis vinifera (cv Sangiovese) induces extensive transcriptome reprogramming and modifies berry ripening

<p>Abstract</p> <p>Background</p> <p>Cluster thinning is an agronomic practice in which a proportion of berry clusters are removed from the vine to increase the source/sink ratio and improve the quality of the remaining berries. Until now no transcriptomic data have been reported describing the mechanisms that underlie the agronomic and biochemical effects of thinning.</p> <p>Results</p> <p>We profiled the transcriptome of <it>Vitis vinifera </it>cv. Sangiovese berries before and after thinning at veraison using a genome-wide microarray representing all grapevine genes listed in the latest V1 gene prediction. Thinning increased the source/sink ratio from 0.6 to 1.2 m²leaf area per kg of berries and boosted the sugar and anthocyanin content at harvest. Extensive transcriptome remodeling was observed in thinned vines 2 weeks after thinning and at ripening. This included the enhanced modulation of genes that are normally regulated during berry development and the induction of a large set of genes that are not usually expressed.</p> <p>Conclusion</p> <p>Cluster thinning has a profound effect on several important cellular processes and metabolic pathways including carbohydrate metabolism and the synthesis and transport of secondary products. The integrated agronomic, biochemical and transcriptomic data revealed that the positive impact of cluster thinning on final berry composition reflects a much more complex outcome than simply enhancing the normal ripening process.</p

On the Origin and Spread of the Scab Disease of Apple: Out of Central Asia

Background Venturia inaequalis is an ascomycete fungus responsible for apple scab, a disease that has invaded almost all apple growing regions worldwide, with the corresponding adverse effects on apple production. Monitoring and predicting the effectiveness of intervention strategies require knowledge of the origin, introduction pathways, and population biology of pathogen populations. Analysis of the variation of genetic markers using the inferential framework of population genetics offers the potential to retrieve this information. Methodology/Principal Findings Here, we present a population genetic analysis of microsatellite variation in 1,273 strains of V. inaequalis representing 28 orchard samples from seven regions in five continents. Analysis of molecular variance revealed that most of the variation (88%) was distributed within localities, which is consistent with extensive historical migrations of the fungus among and within regions. Despite this shallow population structure, clustering analyses partitioned the data set into separate groups corresponding roughly to geography, indicating that each region hosts a distinct population of the fungus. Comparison of the levels of variability among populations, along with coalescent analyses of migration models and estimates of genetic distances, was consistent with a scenario in which the fungus emerged in Central Asia, where apple was domesticated, before its introduction into Europe and, more recently, into other continents with the expansion of apple growing. Across the novel range, levels of variability pointed to multiple introductions and all populations displayed signatures of significant post-introduction increases in population size. Most populations exhibited high genotypic diversity and random association of alleles across loci, indicating recombination both in native and introduced areas. Conclusions/Significance Venturia inaequalis is a model of invasive phytopathogenic fungus that has now reached the ultimate stage of the invasion process with a broad geographic distribution and well-established populations displaying high genetic variability, regular sexual reproduction, and demographic expansion.Contexte Venturia inaequalis est un champignon ascomycete responsable de la tavelure du pommier, une maladie qui a envahi presque toutes les régions du monde où le pommier est cultivé posant ainsi de graves problèmes en production. Prévenir et enrayer efficacement la réussite d’un tel succès invasif nécessite des connaissances approfondies sur l’origine, les voies d’introduction, la biologie et la génétique de ces populations invasives. En utilisant le potentiel d’inférence de la génétique des populations, l’analyse de la variation de marqueurs génétiques offre la possibilité d’accéder à ces informations. Méthodologie et Principaux résultats Ici nous présentons l’analyse de données microsatellites obtenues pour 1273 souches de V. inaequalis provenant de 28 vergers prélevées dans 7 régions sur les 5 continents. L’analyse de la variance moléculaire révèle que 88% de la variation se retrouve dans les vergers échantillonnés, ce qui est compatible avec d’importantes migrations historiques du champignon entre et à l’intérieur même des régions. Malgré cette très faible structuration des populations, les différentes analyses de clustering mettent en évidence un partage des populations en groupes séparés correspondant à leur origine géographique, montrant ainsi que chaque région héberge une population distincte du champignon. Ensemble, les résultats obtenus sur la comparaison du niveau de variabilité entre populations, les analyses de coalescence et les modèles de migration testés plaident en faveur d’un scénario dans lequel le champignon aurait émergé d’Asie Centrale, où le pommier a été domestiqué, avant d’être introduit en Europe puis plus récemment dans les autres continents suite à l’expansion de la culture du pommier. Les niveaux de variabilité indiquent que ces territoires ont subi des introductions multiples et que les populations portent toutes des signatures révélant de fortes expansions démographiques après leur introduction. Enfin, la forte diversité génotypique des populations et l’association aléatoire des allèles entre loci suggèrent que le champignon présente une reproduction sexuée régulière à la fois dans les régions où il a été introduit et dans sa région native. Conclusion et Portée. Venturia inaequalis est un modèle de champignons phytopathogène invasif qui a maintenant atteint le stade ultime du processus invasif, c’est à dire une très large distribution géographique par des populations bien établies montrant une grande diversité génétique, une reproduction sexuée régulière et une histoire d’expansion démographique

Berry Flesh and Skin Ripening Features in Vitis vinifera as Assessed by Transcriptional Profiling

Background Ripening of fleshy fruit is a complex developmental process involving the differentiation of tissues with separate functions. During grapevine berry ripening important processes contributing to table and wine grape quality take place, some of them flesh- or skin-specific. In this study, transcriptional profiles throughout flesh and skin ripening were followed during two different seasons in a table grape cultivar ‘Muscat Hamburg’ to determine tissue-specific as well as common developmental programs. Methodology/Principal Findings Using an updated GrapeGen Affymetrix GeneChip® annotation based on grapevine 12×v1 gene predictions, 2188 differentially accumulated transcripts between flesh and skin and 2839 transcripts differentially accumulated throughout ripening in the same manner in both tissues were identified. Transcriptional profiles were dominated by changes at the beginning of veraison which affect both pericarp tissues, although frequently delayed or with lower intensity in the skin than in the flesh. Functional enrichment analysis identified the decay on biosynthetic processes, photosynthesis and transport as a major part of the program delayed in the skin. In addition, a higher number of functional categories, including several related to macromolecule transport and phenylpropanoid and lipid biosynthesis, were over-represented in transcripts accumulated to higher levels in the skin. Functional enrichment also indicated auxin, gibberellins and bHLH transcription factors to take part in the regulation of pre-veraison processes in the pericarp, whereas WRKY and C2H2 family transcription factors seems to more specifically participate in the regulation of skin and flesh ripening, respectively. Conclusions/Significance A transcriptomic analysis indicates that a large part of the ripening program is shared by both pericarp tissues despite some components are delayed in the skin. In addition, important tissue differences are present from early stages prior to the ripening onset including tissue-specific regulators. Altogether, these findings provide key elements to understand berry ripening and its differential regulation in flesh and skin.This study was financially supported by GrapeGen Project funded by Genoma España within a collaborative agreement with Genome Canada. The authors also thank The Ministerio de Ciencia e Innovacion for project BIO2008-03892 and a bilateral collaborative grant with Argentina (AR2009-0021). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewe

On the origin and spread of the scab disease of apple: out of Central Asia.

Disponível também no formato online

Sprouting of paradormant and endodormant grapevine buds under conditions of forced growth: similarities and differences

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. Main conclusion: Bud-break assays under forced growth conditions suggest that a drop in ABA content and an increase in sugars are common features in the sprouting of paradormant (PD) and endodormant (ED) grapevine buds. However, increases in cell division and in respiration are unique characteristics of the ED budding. In tropical and subtropical regions where the variations in day length and temperatures are minor throughout the year, the rupture of grapevine buds can be achieved during the current growing season given rise to a double-cropping system annually. However, it is unknown whether the breaking buds are in the paradormancy (PD) or endodormancy (ED) stage. In this study, we compared the breakage of PD and ED buds under conditions of forced growth. To do this, the expression of genes related to the metabolism of phytohormones and sugars, and of relevant physiological functions such as respiration and cell divisio