The Ubiquitin-26S Proteasome Pathway and Its Role in the Ripening of Fleshy Fruits.

The 26S proteasome is an ATP-dependent proteolytic complex in eukaryotes, which is mainly responsible for the degradation of damaged and misfolded proteins and some regulatory proteins in cells, and it is essential to maintain the balance of protein levels in the cell. The ubiquitin-26S proteasome pathway, which targets a wide range of protein substrates in plants, is an important post-translational regulatory mechanism involved in various stages of plant growth and development and in the maturation process of fleshy fruits. Fleshy fruit ripening is a complex biological process, which is the sum of a series of physiological and biochemical reactions, including the biosynthesis and signal transduction of ripening related hormones, pigment metabolism, fruit texture changes and the formation of nutritional quality. This paper reviews the structure of the 26S proteasome and the mechanism of the ubiquitin-26S proteasome pathway, and it summarizes the function of this pathway in the ripening process of fleshy fruits.

Molecular and Genetic Events Determining the Softening of Fleshy Fruits: A Comprehensive Review.

Fruit softening that occurs during fruit ripening and postharvest storage determines the fruit quality, shelf life and commercial value and makes fruits more attractive for seed dispersal. In addition, over-softening results in fruit eventual decay, render fruit susceptible to invasion by opportunistic pathogens. Many studies have been conducted to reveal how fruit softens and how to control softening. However, softening is a complex and delicate life process, including physiological, biochemical and metabolic changes, which are closely related to each other and are affected by environmental conditions such as temperature, humidity and light. In this review, the current knowledge regarding fruit softening mechanisms is summarized from cell wall metabolism (cell wall structure changes and cell-wall-degrading enzymes), plant hormones (ETH, ABA, IAA and BR et al.), transcription factors (MADS-Box, AP2/ERF, NAC, MYB and BZR) and epigenetics (DNA methylation, histone demethylation and histone acetylation) and a diagram of the regulatory relationship between these factors is provided. It will provide reference for the cultivation of anti-softening fruits.

Assessment of Various Machine Learning Models for Peach Maturity Prediction Using Non-Destructive Sensor Data.

To date, many machine learning models have been used for peach maturity prediction using non-destructive data, but no performance comparison of the models on these datasets has been conducted. In this study, eight machine learning models were trained on a dataset containing data from 180 'Suncrest' peaches. Before the models were trained, the dataset was subjected to dimensionality reduction using the least absolute shrinkage and selection operator (LASSO) regularization, and 8 input variables (out of 29) were chosen. At the same time, a subgroup consisting of the peach ground color measurements was singled out by dividing the set of variables into three subgroups and by using group LASSO regularization. This type of variable subgroup selection provided valuable information on the contribution of specific groups of peach traits to the maturity prediction. The area under the receiver operating characteristic curve (AUC) values of the selected models were compared, and the artificial neural network (ANN) model achieved the best performance, with an average AUC of 0.782. The second-best machine learning model was linear discriminant analysis with an AUC of 0.766, followed by logistic regression, gradient boosting machine, random forest, support vector machines, a classification and regression trees model, and k-nearest neighbors. Although the primary parameter used to determine the performance of the model was AUC, accuracy, F1 score, and kappa served as control parameters and ultimately confirmed the obtained results. By outperforming other models, ANN proved to be the most accurate model for peach maturity prediction on the given dataset.

Re-evaluation of the nor mutation and the role of the NAC-NOR transcription factor in tomato fruit ripening.

The tomato non-ripening (nor) mutant generates a truncated 186-amino-acid protein (NOR186) and has been demonstrated previously to be a gain-of-function mutant. Here, we provide more evidence to support this view and answer the open question of whether the NAC-NOR gene is important in fruit ripening. Overexpression of NAC-NOR in the nor mutant did not restore the full ripening phenotype. Further analysis showed that the truncated NOR186 protein is located in the nucleus and binds to but does not activate the promoters of 1-aminocyclopropane-1-carboxylic acid synthase2 (SlACS2), geranylgeranyl diphosphate synthase2 (SlGgpps2), and pectate lyase (SlPL), which are involved in ethylene biosynthesis, carotenoid accumulation, and fruit softening, respectively. The activation of the promoters by the wild-type NOR protein can be inhibited by the mutant NOR186 protein. On the other hand, ethylene synthesis, carotenoid accumulation, and fruit softening were significantly inhibited in CR-NOR (CRISPR/Cas9-edited NAC-NOR) fruit compared with the wild-type, but much less severely affected than in the nor mutant, while they were accelerated in OE-NOR (overexpressed NAC-NOR) fruit. These data further indicated that nor is a gain-of-function mutation and NAC-NOR plays a significant role in ripening of wild-type fruit.

The profile of organic acids and polyphenols in apple wines fermented with different yeast strains.

Influence of two apple cultivars (cvs. Cripps Pink and Idared) and two commercial strains of Saccharomyces bayanus (Lalvin EC1118, Fermol Blanc) on the chemical composition and sensory characteristics of apple wines was tested. Chemical parameters (alcohol, sugar-free extract, reducing sugars, titratable and volatile acidity) of the analyzed wines were strongly affected by apple variety. Ash and sugar-free extracts in Cripps Pink wines were significantly higher than Idared wines. Polyphenols and main organic acids were determined in apple juice and wines. Chlorogenic acid was the most abundant polyphenolic compound with the significantly higher concentrations detected for Idared wines. Total phenolic acids, as well as total flavan-3-ols content, were also higher for wines made from Idared variety where fermentation was conducted with Fermol blanc yeast. Among organic acids significantly higher succinic acid content was determined in wines where Fermol Blanc yeast was used while Lalvine EC1118, irrespective of apple variety, significantly influenced the concentration of lactic acid. Sensory evaluation showed the pronounced influence of variety but also the yeast used, singling out Idared cultivar and Fermol Blanc yeast achieving the best overall quality results.

The effects of postharvest application of lecithin to improve storage potential and quality of fresh goji (Lycium barbarum L.) berries.

To enhance storage life and post-storage quality of fresh goji berries, three treatments with lecithin (1, 5, 10g·L-1) and two storage times (8, 16days) were evaluated. The significant effects on the physiological and biochemical parameters were varied. 1g·L-1 lecithin showed its main effects after 8days of storage by reduction in total weight loss and decay, SSC/TA ratio (also at 16days), and chlorophyll content and with highest scores of sensory attributes (also at 16days). 5g·L-1 lecithin showed its main effects after 16days of storage: highest SSC, highest TA (also at 8days), highest TPC, only significant reduction in DPPH antioxidant activity, and highest total flavonoid content. 10g·L-1 lecithin showed its main effects after 8days of storage with highest SSC, chlorophyll content, total flavonoid, DPPH, and ABTS antioxidant activity (also at 16days), but with least scores of sensory attributes.