Diacylglycerol kinase (DGK) is a lipid kinase that phosphorylates diacylglycerol (DAG) to generate phosphatidic acid (PA). Based on converting one important signaling molecule (DAG) to another (PA), DGK plays an important role in plant responses to abiotic stress, including waterlogging stress. However, no studies have been reported on the characterization of the DGK gene family in the waterlogging-tolerant kiwifruit germplasm Actinidia valvata Dunn. In this study, we identified 18 AvDGK genes in the A. valvata genome. The phylogenetic analysis showed that AvDGKs can be classified into three clusters, and members within the same cluster have similar domain distributions, exon-intron structures, and conserved motif compositions. The chromosome localization analysis revealed that all AvDGK genes are located across 18 different chromosomes. There were 29 duplicated gene pairs in A. valvata and all had undergone purifying selection during evolution. The promoter cis-element analysis revealed that the cis-elements within AvDGK genes are associated with multiple functions, including phytohormone signal transduction, stress responses, and plant growth and development. The expression pattern analyses indicated that AvDGKs play important roles in fruit development and plant responses to waterlogging stress. The AvDGK gene family in the tetraploid A. valvata genome might promote PA synthesis and subsequent signal transduction both under short- and long-term waterlogging stresses. These results provide information regarding the structural characteristics and potential function of AvDGK genes within A. valvata and lay a fundamental basis for further research into breeding to enhance the kiwifruit’s tolerance to waterlogging stress.

Long-chain acyl-CoA synthetases (LACSs) are involved in fatty acid metabolism and catabolism by converting free fatty acids to acyl-CoAs. They are essential for initiating β-oxidation of fatty acids and regulating lipid biosynthesis in plant growth and development, as well as in plant adaptation to various environmental stresses, including waterlogging stress. However, systematic identification and functional characterization of the LACS gene family have not been comprehensively studied in the waterlogging-tolerant kiwifruit germplasm Actinidia valvata Dunn. In this study, 22 AvLACS genes were identified within the A. valvata genome. The AvLACS genes were subsequently divided into five clusters on the basis of their phylogenetic relationships, and similar subcellular localizations, exon-intron structures, motif compositions, and protein tertiary structures were found within each cluster. Collinearity analysis identified 22 duplicated gene pairs in A. valvata, and these pairs have undergone purifying selection during evolution. Cis-acting element analysis revealed numerous hormone-responsive and stress-responsive elements in the promoter regions of the AvLACS genes. The expression levels of the AvLACS genes under waterlogging stress were determined using quantitative real-time PCR (qRT-PCR), and the results showed that the expression of the AvLACS1.1a/b, AvLACS1.2a, and AvLACS6a/b was significantly upregulated under waterlogging stress. Notably, AvLACS1.1a/b and AvLACS1.2a primarily facilitate short-term regulation of wax and triacylglycerol (TAG) synthesis, whereas AvLACS6a/b mediate TAG degradation through fatty acid β-oxidation during prolonged waterlogging. Transcriptome data revealed coordinated transcriptional regulation of TAG degradation pathway genes, which was supported by biochemical lipid profiling showing dynamic alterations in TAG content and degree of unsaturation correlated with waterlogging duration. These integrated molecular and biochemical data provide mechanistic insights highlighting distinct and coordinated roles of AvLACSs in lipid metabolic remodeling under waterlogging stress. These findings advance our understanding of the molecular mechanisms underlying waterlogging tolerance, and provide molecular targets and a theoretical basis for breeding waterlogging-tolerant kiwifruit and other crops.

Diacylglycerol kinase (DGK) is a lipid kinase that phosphorylates diacylglycerol (DAG) to generate phosphatidic acid (PA). Based on converting one important signaling molecule (DAG) to another (PA), DGK plays an important role in plant responses to abiotic stress including waterlogging stress. However, no studies have been reported on the characterization of the DGK gene family in the waterlogging-tolerant kiwifruit germplasm, Actinidia valvata Dunn. Here, we identified 18 AvDGK genes in the A. valvata genome. The phylogenetic analysis showed that AvDGKs can be classified into three clusters, and members within the same cluster have similar domain distribution, exon-intron structures and conserved motif compositions. Chromosome localization analysis revealed that all the AvDGK genes are located across 18 different chromosomes. There were 29 duplicated gene pairs in kiwifruit and all had undergone purifying selection during evolution. Promoter cis-element analysis revealed that the cis-elements within AvDGK genes are associated with multiple functions, including phytohormone signal transduction, stress response, and plant growth and development. The expression pattern analyses indicated that AvDGK play an important role in the fruit development and plant response to waterlogging stress. AvDGKs gene family in the tetraploid A. valvata genome might promote PA synthesis and subsequent signal transduction both under short-term and long-term waterlogging stress. These results provide information regarding the structural characteristics and potential function of DGK genes within kiwifruit and lay a fundamental basis for further research into breeding for enhancing the kiwifruit’s tolerance to waterlogging stress.