Genetic identification and genomic organization of factors affecting fruit texture.
ABSTRACT Fleshy fruits are an essential part of the human diet providing vital vitamins, minerals and other health-promoting compounds. The texture of the ripe fruit has a significant effect on quality and influences consumer acceptance, shelf-life, resistance, and transportability. The development of rational approaches to improve texture and shelf-life depend on understanding the biological basis of fruit ripening. Until recently, work has focused on the isolation of ripening-related genes from a variety of fleshy fruits. However, little is known about the genes that regulate this complex developmental process or whether similar regulatory genes are active in all fruiting species. A major breakthrough would be the identification of generic genes associated with texture and other aspects of ripening in fleshy fruits. In tomato, a small number of single gene mutations exist, such as ripening-inhibitor (rin), non-ripening (nor), Never-ripe (Nr), and Colourless non-ripening (Cnr) which have pleiotropic effects resulting in the reduction or almost complete abolition of ripening. These mutations probably represent lesions in regulatory genes. The cloning of the wild-type alleles of RIN and NOR is reported by Moore et al. in this issue. This review focuses on the texture characteristics of the Cnr mutant. A possible framework for the molecular regulation of fruit texture is discussed and quantitative genetic approaches to determining the generic attributes of fruit texture are explored.
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ABSTRACT: Medlar (Mespilus germanica L. cv. Istanbul) fruit were stored in palliflex controlled atmosphere storage systems of 21% O2 + 0.03% CO2 (PL-1, control), 2% O2 + 5% CO2 (PL-2), 3% O2 + 10% CO2 (PL-3) and modified atmosphere packaging (MAP) at 0 °C for 60 days to determine the effects of different O2 and CO2 concentrations on physiological properties, quality attributes and storability. Every 15 days, three replicates of each treatment were evaluated for weight loss, fruit firmness, decay, external browning index, skin color, pH, titratable acidity, total soluble solids, total phenolics, total flavonoids, total condensed tannins, ascorbic acid, antioxidant activity and organic acid and sugar contents. Taste analysis of the fruit was performed after 30, 45 and 60 days of storage. The CO2 and O2 concentrations created by the MAP stabilized at 7% and 14%, respectively. Weight loss of fruit stored in MAP was lower (<0.4% at 60 days) than for other treatments. Off-flavors were not detected in any treatment. Storage of medlar fruit under PL-3 was the least effective treatment in delaying fruit ripening (flesh firmness). The incidence and severity of browning, loss of skin color (Ch°) and retaining acceptable taste during 60 days were found the most effective in PL-2 and PL-1 compared to other treatments. Fruit pH increased and titratable acidity decreased during the storage period. Total soluble solids and sugar contents first increased then decreased in all treatments by the end of storage. The fruit stored in PL-2 had higher titratable acidity, total soluble solids and sugar contents than fruit stored in PL-1, PL-3 and MAP at all evaluations. Concentrations of total phenolics, total flavonoids, total condensed tannins, ascorbic acid, associated antioxidant activity and organic acids were affected by the storage atmosphere, decreased during storage. The concentrations of total phenolics, total flavonoids, and antioxidant activity were found the highest in PL-2, PL-1 and MAP treatments, respectively. However, in terms of ascorbic acid and total condensed tannins retention, PL-2 was the most effective treatments. The results indicated that 60 days storage of medlar fruit in the palliflex storage system at 0 °C maintained physiological and biochemical properties of medlar fruit.Postharvest Biology and Technology 01/2015; 99:9–19. · 2.63 Impact Factor
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ABSTRACT: Background Apple fruit mealiness is one of the most important textural problems that results from an undesirable ripening process during storage. This phenotype is characterized by textural deterioration described as soft, grainy and dry fruit. Despite several studies, little is known about mealiness development and the associated molecular events. In this study, we integrated phenotypic, microscopic, transcriptomic and biochemical analyses to gain insights into the molecular basis of mealiness development.ResultsInstrumental texture characterization allowed the refinement of the definition of apple mealiness. In parallel, a new and simple quantitative test to assess this phenotype was developed.Six individuals with contrasting mealiness were selected among a progeny and used to perform a global transcriptome analysis during fruit development and cold storage. Potential candidate genes associated with the initiation of mealiness were identified. Amongst these, the expression profile of an early down-regulated transcript similar to an Arabidopsis thaliana pectin methylesterase gene (AtPME2) matched with mealiness development. In silico analyses of this Malus x domestica PME gene (MdPME2) confirmed its specific pattern compared with all other identified MdPME genes. Protein fusion experiments showed that MdPME2 is secreted into the apoplast in accordance with a possible activity on pectin structure. Further microscopic analysis indicated a progressive loss of cell to cell adhesion in mealy apple fruits. Biochemical analysis revealed specific modifications of pectin residues associated with mealiness, without global changes in the degree of methylesterification of pectins.Conclusions These data support the role of PME in cell wall remodelling during apple fruit development and ripening and suggest a local action of these enzymes. Mealiness may partially result from qualitative and spatial variations of pectin microarchitecture rather than quantitative pectin differences, and these changes may occur early in fruit development. The specific MdPME2 gene highlighted in this study could be a good early marker of texture unfavourable trait in apple.BMC Plant Biology 12/2014; 14(1):1593. · 3.94 Impact Factor
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ABSTRACT: Tomato is one of the most cultivated vegetables in the world and an important ingredient of the human diet. Tomato breeders and growers face a continuous challenge of combining high quantity (production volume) with high quality (appearance, taste and perception for the consumers, processing quality for the processing industry). To improve the quality of tomato, it is important to understand the regulation of fruit development and of fruit cellular structure, which is in part determined by the sizes and numbers of cells within a tissue. The role of the cell cycle therein is poorly understood. Plant cyclin-dependent kinases (CDKs) are homologues of yeast cdc2, an important cell cycle regulator conserved throughout all eukaryotes. CDKA1 is constitutively expressed during the cell cycle and has dual functions in S- and M-phase progression. We have produced transgenic tomato plants with increased expression of CDKA1 under the control of the fruit-specific TPRP promoter, which despite a reduced number of seeds and diminished amount of jelly, developed fruits with weight and shape comparable to that of wild-type fruits. However, the phenotypic changes with regard to the pericarp thickness and placenta area were remarkable. Fruits of tomato plants with the highest expression of CDKA1 had larger septa and columella (placenta), compared with wild-type fruits. Our data demonstrate the possibility of manipulating the ratio between cell division and expansion by changing the expression of a key cell cycle regulator and probably its activity with substantial effects on structural traits of the harvested fruit.Plant Biotechnology Journal 02/2015; 13(2):259-268. · 6.28 Impact Factor