Walnut (Juglans regia) is an important woody oil-bearing plant with high nutritional value. For better understanding of the underlying molecular mechanisms of its oil accumulation in the Qinghai Plateau, in this study we monitored walnut fruit development, and 15 cDNA libraries were constructed from walnut seed kernels collected at 72, 79, 93, 118 and 135 days after flowering (DAF). The candidate genes were identified using sequencing and expression analysis. The results showed that the oil content in the kernels increased dramatically in late July and reached the maximum value of 69% in mature seed. More than 90% of the oils were unsaturated fatty acids (UFAs) and linoleic acid (18:2) was the predominant UFA accumulated in mature seed. Differentially expressed genes (DEGs) in 15 KEGG pathways of lipid metabolism were detected. We identified 119 DEGs related to FA de novo biosynthesis (38 DEGs), FA elongation and desaturation (39 DEGs), triacylglycerol (TAG) assembly (24 DEGs), oil bodies (12 DEGs), and transcription factors (TFs, 6 DEGs). The abundantly expressed oleosins, caleosins and steroleosins may be important for timely energy reserve in oil bodies. Weighted gene coexpression network analysis (WGCNA) showed that AP2/ERF and bHLH were the key TFs, and were co-expressed with ACC1, α-CT, BCCP, MAT, KASII, LACS, FATA, and PDCT. Our transcriptome data will enrich public databases and provide new insights into functional genes related to the seed kernel lipid metabolism and oil accumulation in J. regia.

Goji, a renowned traditional Chinese medicine and food source, is characterized by a long fruiting period. This study was conducted to investigate the variations in nutritional quality of goji berries across different harvest stages by utilizing widely targeted metabolome and transcriptome. The results showed that goji berries of the first harvest stage had advantages in terms of size and metabolic levels, and there was little difference in sugars and organic acids levels. Within significantly enriched phenylpropanoid and flavonoid pathways, chlorogenic acid, and its positional isomers (neochlorogenic acid and cryptochlorogenic acid) increased significantly along with P‐coumaroyl quinic acid as the harvest stages progressed, while the other bioactive DEMs including scopoletin, scopolin, naringenin, and pruning exhibited a decreasing trend. The key DEGs encoding PAL, HCT, 4CL, C4H, TOGT1, and C12RT1 were suggested to regulate the variations of these DEMs. Furthermore, six oxidative metabolites enriched in alpha‐linolenic acid and linoleic acid metabolism pathways all peaked at the second harvest stage. Climate or plant weakening is suggested as potential factors influencing the metabolic and transcriptomic changes in goji berries. This study provides a fresh perspective on understanding the accumulation of metabolites and their molecular mechanisms in goji at different harvest stages in the Qaidam Basin and can be used to guide goji production and processing.

The stability of internal reference genes is of great significance for the study of gene functions, and the development and screening of stable internal reference genes is the key to gene function analysis. Real-time reverse transcription quantitative PCR (qPCR) is an important tool to measure gene expression levels. Selection of stable reference genes for data normalization is a prerequisite. To date, the lack of studies on validation of reference genes in Ribes odoratum limits application of qPCR in Ribes odoratum. In this study, Through drought stress treatments and transcriptome analysis of Ribes odoratum, this study identified multiple genes with stable expression under drought stress. The expression stability of 17 candidate reference genes under drought stress was evaluated using the Genorm, NormFinder, BestKeeper, and Delta Ct algorithms. The results showed that Cluster-37.22228, Cluster-37.22646 and Cluster-37.22897 were the top three stable reference genes, and the best reference genes that could be used as internal controls in Ribes odoratum was Cluster-37.22228 and Cluster-37.22646. These results provided for the first time a comprehensive list of stable reference genes for the normalization of qPCR analyses in Ribes odoratum under drought stress and will benefit the in-depth molecular biology research in the future.