FaGAPC2/FaPKc2.2 and FaPEPCK reveal differential citric acid metabolism regulation in late development of strawberry fruit

Citric acid is the primary organic acid that affects the taste of strawberry fruit. Glycolysis supplies key substrates for the tricarboxylic acid cycle (TCA cycle). However, little is known about the regulatory mechanisms of glycolytic genes on citric acid metabolism in strawberry fruits. In this study, the citric acid content of strawberry fruit displayed a trend of rising and decreasing from the initial red stage to the full red stage and then dark red stage. Thus, a difference in citric acid metabolic regulation was suspected during strawberry fruit development. In addition, overexpression of either cytoplasm glyceraldehyde-3-phosphate dehydrogenase (FxaC_14g13400, namely FaGAPC2) or pyruvate kinase (FxaC_15g00080, namely FaPKc2.2) inhibited strawberry fruit ripening and the accumulation of citric acid, leading to a range of maturity stages from partial red to full red stage. The combined transcriptome and metabolome analysis revealed that overexpression of FaGAPC2 and FaPKc2.2 significantly suppressed the expression of phosphoenolpyruvate carboxykinase (FxaC_1g21491, namely FaPEPCK) but enhanced the content of glutamine and aspartic acid. Meanwhile, the activities of PEPCK and glutamate decarboxylase (GAD) were inhibited, but the activities of glutamine synthase (GS) were increased in FaGAPC2/FaPKc2.2-overexpressed fruit. Further, functional verification demonstrated that overexpression of FaPEPCK can promote strawberry fruit ripening, resulting in a range of maturity stage from full red to dark red stage, while the citric acid synthase (CS) activities and citric acid content were significantly decreased. Overall, this study revealed that FaGAPC2/FaPKc2.2 and FaPEPCK perform an important role in reducing citric acid content in strawberry fruit, and FaGAPC2/FaPKc2.2 mainly by promoting the GS degradation pathway and FaPEPCK mainly by inhibiting the CS synthesis pathway

Comparative transcriptome analysis uncovers the regulatory functions of long noncoding RNAs in fruit development and color changes of Fragaria pentaphylla

Ripening: What makes strawberries turn red? Researchers have pinpointed key genes that make strawberries turn red when they ripen. The role of hormones in fruit ripening has been extensively studied, but questions remain about the underlying genetics. Haoru Tang at Sichuan Agricultural University in China and co-workers assembled detailed genetic profiles of two wild strawberry varieties, one with red and the other with white fruits, at three stages of ripening. They focused on long non-coding RNAs (lncRNAs), master switches of gene regulation. Identifying differences in lncRNA profiles between the varieties allowed them to trace the complex genetic networks controlling ripening and redness. They also identified two key genes that generate red pigment, which are switched off in the white fruits. These results illuminate the complex genetics underlying a key feature of one of the world’s most economically important fruits. Researchers have illuminated the genetic cues that control the ripening of strawberries by comparing the genes switched on two variants, that produce red or white fruits, respectively

Pre-Harvest Application of Strigolactone (GR24) Accelerates Strawberry Ripening and Improves Fruit Quality

GR24, a synthetic strigolactone analogue, plays a crucial role in a wide range of life processes. Studying the effects of the pre-harvest application of GR24 on strawberry ripening and fruit quality provides a scientific basis for the application of GR24 in horticultural crop production. GR24 solutions at concentrations of 0, 0.5, 1 and 2 µmol/L were applied to strawberries at the de-greening stage. The results showed that pre-harvest treatment with 1 µmol/L GR24 increased fruit weight and size; promoted fruit softening; increased the content of sugars, total flavonoids, total phenolics, and anthocyanins, and increased antioxidant activity. These results proved that GR24 effectively accelerated fruit ripening and improved fruit quality. In addition, to gain more insight into the biological mechanism of GR24 in fruit ripening, we conducted a combined transcriptomic and metabolomic analysis. It was found that the differences were related to sugar and flavonoid biosynthesis, particularly in the later stage of fruit ripening. qRT-PCR analysis revealed that GR24 increased gene expression activity and metabolite accumulation in the anthocyanin and sugar biosynthetic pathway, thereby promoting strawberry color and flavor