Cranberries (Vaccinium macrocarpon Ait.), renowned for their excellent health benefits, are an important berry crop. Here, we performed transcriptome sequencing of one cranberry cultivar, from fruits at two different developmental stages, on the Illumina HiSeq 2000 platform. Our main goals were to identify putative genes for major metabolic pathways of bioactive compounds and compare the expression patterns between white fruit (W) and red fruit (R) in cranberry. In this study, two cDNA libraries of W and R were constructed. Approximately 119 million raw sequencing reads were generated and assembled de novo, yielding 57,331 high quality unigenes with an average length of 739 bp. Using BLASTx, 38,460 unigenes were identified as putative homologs of annotated sequences in public protein databases, including NCBI NR, NT, Swiss-Prot, KEGG, COG and GO. Of these, 21,898 unigenes mapped to 128 KEGG pathways, with the metabolic pathways, secondary metabolites, glycerophospholipid metabolism, ether lipid metabolism, starch and sucrose metabolism, purine metabolism, and pyrimidine metabolism being well represented. Among them, many candidate genes were involved in flavonoid biosynthesis, transport and regulation. Furthermore, digital gene expression (DEG) analysis identified 3,257 unigenes that were differentially expressed between the two fruit developmental stages. In addition, 14,473 simple sequence repeats (SSRs) were detected. Our results present comprehensive gene expression information about the cranberry fruit transcriptome that could facilitate our understanding of the molecular mechanisms of fruit development in cranberries. Although it will be necessary to validate the functions carried out by these genes, these results could be used to improve the quality of breeding programs for the cranberry and related species.

Cranberry is a small fruit crop with great development potential. Due to its shallow root system and dominance of fibrous roots, it is highly susceptible to drought stress, but the response mechanism is still unclear. In this study, “Bain 11” cranberry was used as the material, and four pot treatments were set up: normal water supply (CK), mild (D1), moderate (D2), and severe (D3) drought. After reaching the set stress levels, functional leaves were collected. The response mechanism to different degrees of drought was clarified by combining paraffin sectioning, chlorophyll fluorescence, spectrophotometry, and transcriptome sequencing technology. The results showed that there was no significant change in the rate of photosynthetic oxygen release under D1 conditions; under D2 conditions, the function of PSII was impaired, but the heat dissipation capacity was enhanced, and the protective mechanism was activated; under D3 conditions, the performance of both PSII and PSI was significantly inhibited, the damage to the oxygen-evolving complex was the most severe, and the photosynthetic oxygen production decreased significantly. Leaf anatomical structure showed that with the intensification of drought, the morphology, area, and density of stomata changed, and the thickness of palisade tissue, epidermis, and spongy tissue decreased; under D2 conditions, organelle membranes were deformed but intact, and the thylakoid lamellar spacing increased; under D3 conditions, organelle membranes ruptured, nuclear material leaked, chloroplasts vacuolated, and thylakoid lamellae disintegrated. The oxidative stress indicators MDA and H ₂ O ₂ increased with the intensity of the stress, and the activities of SOD and CAT significantly increased under D2 and D3 conditions. Transcriptome sequencing identified 58,020 single genes, and KEGG enrichment analysis showed that 55 continuously differentially expressed genes were involved in 54 metabolic pathways (19 upregulated and 36 downregulated), among which photosynthesis-related genes accounted for the highest proportion (13%) and played a key role in the drought response, providing important insights into the drought stress response mechanism of cranberry.

Nitrogen (N) is the most critical element influencing plant growth and development. Different plant species exhibit varying preferences for different N forms. In order to identify an appropriate nutrient solution N formula for optimizing blueberry substrate cultivation, we investigated the effects of seven different NH₄⁺-N/NO₃⁻-N ratios on the growth characteristics, photosynthetic physiology, mineral element content, enzymes related to N metabolism, and fruit quality, with ‘F32’ used as the experimental material and water served as controls. The results demonstrated that both the aboveground and belowground parts of blueberry plants exhibited enhanced growth when NH₄⁺-N was used as the primary N source in the nutrient solution, compared to single NH₄⁺-N or a high NO₃⁻-N ratio. The most significant growth promotion occurred when the NH₄⁺-N to NO₃⁻-N ratio was 7:3. When NH₄⁺-N and NO₃⁻-N are concurrently supplied in the nutrient solution, the processes of NO₃⁻ reduction, the GS-GOGAT cycle, and NH₄⁺ assimilation are significantly enhanced during nitrogen metabolism. Thereby, providing a theoretical foundation for optimizing nutrient solution management in substrate-cultivated blueberry.