Sugar content is a critical indicator of fruit quality and is mainly controlled by sugar transporters. Sugars will eventually be exported transporters (SWEET) proteins play an indispensable role in sugar allocation between and within plant organs. Sucrose is the major sugar in many fruits and the predominant form of sugar translocated in peach (Prunus persica). However, the role of the multiple peach SWEET genes in sucrose allocation to fruit remains elusive. In this study, a total of 19 SWEET candidates have been identified in the peach genome, and two Clade III SWEET genes, PpSWEET9a and PpSWEET14, are found to be highly expressed in mature source leaves and branches. Complementation assays, transgene manipulations, and protein interaction studies reveal that PpSWEET9a and PpSWEET14 serve as sucrose efflux proteins and form a heterooligomer that synergistically directs sucrose allocation from source leaves to fruits. Our findings provide insights into the effect of SWEETs on sugar accumulation in peach fruit and identify genetic candidates for improving fruit quality.

The high accumulation of phloridzin makes apple (Malus domestica) unique in the plant kingdom, which suggests a vital role of its biosynthesis in physiological processes. In our previous study, silencing MdUGT88F1 (a key UDP-GLUCOSE: PHLORETIN 2’-O-GLUCOSYLTRANSFERASE gene) revealed the importance of phloridzin biosynthesis in apple development and Valsa canker resistance. Here, results from MdUGT88F1-silenced lines showed that phloridzin biosynthesis was indispensable for normal chloroplast development and photosynthetic carbon fixation by maintaining MdGLK1/2 (GOLDEN2-like1/2) expression. Interestingly, increased phloridzin biosynthesis did not affect plant (or chloroplast) development, but reduced nitrogen accumulation, leading to chlorophyll deficiency, light sensitivity, and sugar accumulation in MdUGT88F1-overexpressing apple lines. Further analysis revealed that MdUGT88F1-mediated phloridzin biosynthesis negatively regulated the cytosolic glutamine synthetase1-asparagine synthetase-asparaginase (GS1-AS-ASPG) pathway of ammonium assimilation and limited chlorophyll synthesis in apple shoots. The interference of phloridzin biosynthesis in the GS1-AS-ASPG pathway was also assumed to be associated with its limitation of the carbon skeleton of ammonium assimilation through metabolic competition with the tricarboxylic acid cycle. Taken together, our findings shed light on the role of MdUGT88F1-mediated phloridzin biosynthesis in the coordination between carbon and nitrogen accumulation in apple trees.

Chinese plum (Prunus salicina) cv. Wushancuili has a green coloration, high fruit quality, and is economically important in eliminating poverty and protecting ecology in the Yangtze River Three Gorges Reservoir. However, large-scale production and synchronous ripening times present a huge postharvest storage challenge. This study investigated the effect of different postharvest storage temperatures on the ‘Wushancuili’ plum fruit flavor. The dynamics of soluble sugars, organic acids, and aroma substances were investigated at four temperatures mimicking large-scale commercial storage applications: 0–2 °C, 4–6 °C, 8–10 °C, and 20 °C, for 0, 3, 5, 7, 10, 15, and 20 days. Storage under the 0–2 °C regime was the best at preserving fruit flavor and reducing decay compared to the other settings. At 0–2 °C, fruit maintained a stable level of soluble sugars and organic acids during storage. Moreover, this storage temperature facilitated the formation of aroma compounds such as alcohols, aldehydes, ketones, and acids, which contributed to the distinct fruit aromatic characteristics. Taken together, our findings indicate that 0–2 °C is the most favorable temperature for commercial storage and maintenance of the ‘Wushancuili’ plum flavor.

Banana fruits are harvested and then undergo rapid ripening and senescence, sharply limiting their shelf-life and marketability. Myo-inositol (MI) is an important regulator in ethylene production and reactive oxygen species (ROS) accumulation; however, its involvement in the postharvest ripening process of banana remains to be determined. This study found that postharvest application of MI could efficiently delay the fruit ripening and extend the time in which the luster, color, and hardness were maintained in two cultivars with contrasting storage characteristics, storable ‘Brazil’ and unstorable ‘Fenza No. 1’, when stored at room temperature (23 °C ± 2 °C). Moreover, physiological, metabolic, and gene expression analyses indicated that MI application improved MI metabolism and postponed ethylene biosynthesis and cell wall loosening. The decrease in ethylene production was associated with a reduction in the expression of ACS1 and ACO1 genes. MI treatment decreased the expressions of PL1/2, PG, and EXP1/7/8, which may account for the delay in softening. In addition, the application of MI could alleviate ROS-mediated senescence and cell membrane damage by promoting the activities of SOD, POD, and anti-O₂⁻ and decreasing PPO activity. This study shed light on the function of MI in regulating the postharvest ripening and senescence of bananas and provided an efficient strategy for extending shelf-life and reduce losses.