Canarium album fruit has great potential to be consumed as a raw material not only for food but also medicine. The diverse active metabolites composition and content of C. album fruits greatly affect their pharmacological effects. However, up to now, there has been no report on the global metabolome differences among fruits from distinct C. album cultivars. In our present study, by using non-targeted metabolomics techniques, we identified 87 DAMs (differentially accumulated metabolites) including 17 types of flavonoids from fruits of four different C. album cultivars. KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment analysis revealed that the flavone and flavonol biosynthesis- and flavonoid biosynthesis-related DAMs were major factors determining their metabolome differences. Comparative transcriptomic analysis revealed that 15 KEGG pathways were significantly enriched by genes of the identified 3655 DEGs (differentially expressed genes) among different C. album cultivars. Consistent with the metabolome data, flavonoid biosynthesis-related DEGs, including eight key structural genes (such as FLS, CCoAOMT, CHI, C4H, DFR, LAR, and C3′H, etc.) and several regulatory transcription factor (TF) genes (including 32 MYBs and 34 bHLHs, etc.), were found to be significantly enriched (p < 0.01). Our study indicated that the differential expression of flavonoid biosynthesis-related genes and accumulation of flavonoids played dominant roles in the various metabolome compositions of fruits from different C. album cultivars.

Kiwifruit (Actinidia spp.) is susceptible to waterlogging stress. Although abundant wild germplasm resources exist among Actinidia plants for improving the waterlogging tolerance of kiwifruit cultivars, the underlying mechanisms remain largely unknown. Here, a comparative study was undertaken using one wild germplasm, Maorenshen (A. valvata Dunn, MRS), and one cultivar, Miliang-1 (A. chinensis var. deliciosa (A.Chev.) A.Chev. cv. Miliang-1, ML). Under stress, the ML plantlets were seriously damaged with wilted chlorotic leaves and blackened rotten roots, whereas the symptoms of injury in the MRS plantlets were much fewer, along with higher photosynthetic rates, chlorophyll fluorescence characteristics and root activity under stress conditions. However, neither aerenchyma in the root nor adventitious roots appeared in both germplasms upon stress exposure. The activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH), as well as their transcript levels, were constitutively higher in MRS than those in ML under both normal and stress conditions. Waterlogging stress significantly enhanced the PDC and ADH enzyme activities in both germplasms, which were 60.8% and 22.4% higher in the MRS roots than those in the ML roots under waterlogging stress, respectively. Moreover, MRS displayed higher activities of antioxidant enzymes, including SOD, CAT, and APX, as well as DPPH-radical scavenging ability, and decreased H₂O₂ and MDA accumulation under both normal and stress conditions. Our findings suggest that the waterlogging tolerance of the wild A. valvata germplasm was associated with high PDC and ADH, as well as antioxidant ability.

Long non-coding RNAs (lncRNAs) are crucial players regulating many biological processes in plants. However, limited knowledge is available regarding their roles in kiwifruit ripening and softening. In this study, using lncRNA-seq technology, 591 differentially expressed (DE) lncRNAs (DELs) and 3107 DE genes (DEGs) were identified from kiwifruit stored at 4 °C for 1, 2, and 3 weeks in comparison with non-treated control fruits. Of note, 645 DEGs were predicted to be targets of DELs (DEGTLs), including some DE protein-coding genes (such as β-amylase and pectinesterase). DEGTL-based GO enrichment analysis revealed that these genes were significantly enriched in cell wall modification and pectinesterase activity in 1 W vs. CK and 3 W vs. CK, which might be closely related to the fruit softening during low-temperature storage. Moreover, KEGG enrichment analysis revealed that DEGTLs were significantly associated with starch and sucrose metabolism. Our study revealed that lncRNAs play critical regulatory roles in kiwifruit ripening and softening under low-temperature storage, mainly by mediating the expression of starch and sucrose metabolism and cell wall modification related genes.

Kiwifruit is widely cultivated for its high vitamin C content and nutritional value. In January 2022, root rot symptoms were found in about 30% of Actinidia chinensis cv. Jinyan plants grafted on A...

Sugars are key metabolites influencing the flavor and quality of kiwifruit, with their accumulation in fruit relying on sugar transporters. Recently identified sugar transporters known as SWEETs play significant roles in modulating plant growth, development, and fruit ripening. However, the characteristics of SWEET genes in Actinidia eriantha remain poorly understood. In this study, a total of 26 AeSWEET genes were identified across 17 chromosomes. These genes encoded proteins ranging from 198 to 305 amino acids in length and contained 5 to 7 transmembrane helices. Both interspecific and intraspecific phylogenetic trees categorized AeSWEET proteins into four distinct clades. The motif and domain structures were conserved within each clade, although variations were observed in exon-intron organizations. One tandem and fourteen segmental duplication events were identified as primary drivers of the AeSWEET family expansion. Comparative syntenic mapping showed a closer homology of the AeSWEET family with that of dicotyledons compared to monocotyledons. Promoter cis-element analysis indicated the potential responses of AeSWEET genes to five phytohormones and seven environmental stressors. Quantitative real-time PCR analysis revealed tissue-specific expression profiles of AeSWEET genes, with two AeSWEET11 genes (AeSWEET11a and AeSWEET11b) showing significantly higher expression levels in fruit tissues. Their expressions were positively correlated with sucrose, fructose, and glucose contents throughout fruit development and ripening. Transient transformation tests in tobacco leaves verified the predominant localization of AeSWEET11a and AeSWEET11b to the plasma membrane. Functional assays in yeast mutants revealed that AeSWEET11a and AeSWEET11b both possessed sucrose and hexose transport activities. These findings highlight the potential of targeting AeSWEET11a and AeSWEET11b to enhance sugar accumulation in the fruit of A. eriantha, thereby providing a foundation for improving the flavor profile of commercial cultivars.