Transcriptomic and Metabolic Analysis of Fruit Development and Identification of Genes Involved in Raffinose and Hydrolysable Tannin Biosynthesis in Walnuts

Abstract

Walnut (Juglans regia L.) is an important fruit tree with high nutrition in its nuts. Here, the development of walnut fruits was monitored, and nine biological samples at five developmental stages were collected and analyzed by transcriptomic and metabolic assays. Many phenolic metabolites accumulated in the peel of mature fruits, while lipids, carbohydrates, and amino acids and their derivatives mainly accumulated in the kernel. Fatty acid biosynthesis occurred at 13 weeks after pollination, and photosynthesis might occur in the exocarp of walnuts. By coexpression analysis of the transcriptome and metabolome, genes responsible for some metabolic pathways were predicted. Three genes encoding shikimate dehydrogenases (SDHs) that convert 3dehydroshikimic acid to gallic acid (GA) and four genes encoding UDP-glycosyltransferase (UGT) that convert GA to β-glucogallin in the biosynthesis of hydrolysable tannins (HTs) were selected for functional confirmation. These three SDH genes were then expressed in Escherichia coli, and their recombinant proteins showed GA formation activity. Moreover, heterologous expression of the three SDH and four UGT genes in poplar hairy roots also showed a significant increase in GA and β-glucogallin accumulation, respectively. Taken together, we have provided an overview of walnut fruit development and uncovered genes involved in HT biosynthesis.

Mitochondrial pyruvate carrier blockade results in decreased osteoclastogenesis and bone resorption via regulating mitochondrial energy production

“…The following antibodies were used: Novogene Co., Ltd. (Beijing, China). All parameters and conditions were set the same as those used in a previous study (35), and the raw data generated by the LC-MS/MS system were analyzed using the software SCIEX OS Version 1.4 to integrate and correct the chromatographic peak. All metabolomics data were analyzed by the website-based tool MetaboAnalyst (http://www.metaboanalyst.ca).…”

Metabolome and Transcriptome Profiling Unveil the Mechanisms of Polyphenol Synthesis in the Developing Endopleura of Walnut (Juglans regia L.)

“…In addition, 15 DAMs belonged to flavonoid and flavonol biosynthesis ( Figure S2 ), of which 13 metabolites accumulated in greater quantities in the endopleura than that in the embryo. This result was similar to the study of Wang et al [ 20 ].…”

“…A total of 120 metabolites were initially identified, including hydrolyzed and condensed tannins, flavonoids, and phenolic acids. Wang et al [ 20 ] reported that many phenolic metabolites accumulate in the endopleura of mature fruits, while lipids and amino acids and their derivatives mainly accumulate in the embryo. However, the reasons for high polyphenol content in walnut endopleura have not been investigated.…”

Research Progress and Trends in Metabolomics of Fruit Trees

“…The combined analysis with transcriptome data demonstrates that the Asr1 [i.e., abscisic acid (ABA), stress, and ripening 1] transcription factor is involved in the cascade regulation of red tomato fruit maturation (Dominguez et al, 2021). Special metabolites also accumulate in mangosteen (Mamat et al, 2020), ginseng berry (Park et al, 2019), starfruit (Ramadan et al, 2020), avocado (Hurtado-Fernández et al, 2015), strawberry (Zhang et al, 2011;Wang et al, 2021e), apple (Rudell and Mattheis, 2009;Risticevic et al, 2016Risticevic et al, , 2020Jing and Malladi, 2020;Xu et al, 2020), grape berry (Dai et al, 2013), mulberry (Lee et al, 2016), cupressaceae (Falasca et al, 2014), olea (Olmo-García et al, 2018), walnuts (Wang et al, 2021b), and African baobab (Baky et al, 2021) during fruit maturing.…”