Lipid phosphorylation by a diacylglycerol kinase suppresses ABA biosynthesis to regulate plant stress responses

Lipid phosphorylation by diacylglycerol kinase(DGK)that produces phosphatidic acid(PA)plays important roles in various biological processes,including stress responses,but the underlying mechanisms remain elusive.Here,we show that DGK5 and its lipid product PA suppress ABA biosynthesis by interacting withABA-DEFICIENT2(ABA2),a key ABA biosynthesis enzyme,to negatively modulate plant responseto abiotic stress tested in Arabidopsis thaliana.Loss of DGK5 function rendered plants less damaged,whereas overexpression(OE)of DGK5 enhanced plant damage to water and salt stress.The dgk5 mutant plants exhibited decreased total cellular and nuclear levels of PA with increased levels of diacylglycerol,whereas DGK5-OE plants displayed the opposite effect.Interestingly,we found that both DGK5 and PA bind to the ABA-synthesizing enzyme ABA2 and suppress its enzymatic activity.Consistently,the dgk5 mutant plants exhibited increased levels of ABA,while DGK5-OE plants showed reduced ABA levels.In addition,we showed that both DGK5 and ABA2 are detected in and outside the nuclei,and loss of DGK5 function decreased the nuclear association of ABA2.We found that both DGK5 activity and PA promote nuclear association of ABA2.Taken together,these results indicate that both DGK5 and PA interact with ABA2 to inhibit its enzymatic activity and promote its nuclear sequestration,thereby sup-pressing ABA production in response to abiotic stress.Our study reveals a sophisticated mechanism by which DGK5 and PA regulate plant stress responses.

Multiomics analysis reveals metabolic subtypes and identifies diacylglycerol kinase α (DGKA) as a potential therapeutic target for intrahepatic cholangiocarcinoma

Background:Intrahepatic cholangiocarcinoma(iCCA)is a highly heteroge-neous and lethal hepatobiliary tumor with few therapeutic strategies.The metabolic reprogramming of tumor cells plays an essential role in the develop-ment of tumors,while the metabolic molecular classification of iCCA is largely unknown.Here,we performed an integrated multiomics analysis and metabolic classification to depict differences in metabolic characteristics of iCCA patients,hoping to provide a novel perspective to understand and treat iCCA.Methods:We performed integrated multiomics analysis in 116 iCCA samples,including whole-exome sequencing,bulk RNA-sequencing and proteome anal-ysis.Based on the non-negative matrix factorization method and the protein abundance of metabolic genes in human genome-scale metabolic models,the metabolic subtype of iCCA was determined.Survival and prognostic gene analy-ses were used to compare overall survival(OS)differences between metabolic subtypes.Cell proliferation analysis,5-ethynyl-2’-deoxyuridine(EdU)assay,colony formation assay,RNA-sequencing and Western blotting were performed to investigate the molecular mechanisms of diacylglycerol kinaseα(DGKA)in iCCA cells.Results:Three metabolic subtypes(S1-S3)with subtype-specific biomarkers of iCCA were identified.These metabolic subtypes presented with distinct prog-noses,metabolic features,immune microenvironments,and genetic alterations.The S2 subtype with the worst survival showed the activation of some special metabolic processes,immune-suppressed microenvironment and Kirsten ratsar-coma viral oncogene homolog(KRAS)/AT-rich interactive domain 1A(ARID1A)mutations.Among the S2 subtype-specific upregulated proteins,DGKA was further identified as a potential drug target for iCCA,which promoted cell proliferation by enhancing phosphatidic acid(PA)metabolism and activating mitogen-activated protein kinase(MAPK)signaling.Conclusion:Viamultiomics analyses,we identified three metabolic subtypes of iCCA,revealing that the S2 subtype exhibited the poorest survival outcomes.We further identified DGKA as a potential target for the S2 subtype.

Association between diacylglycerol kinase kappa variants and hypospadias susceptibility in a Han Chinese population

Previous genome-wide association studies have identified variants in the diacylglycerol kinase kappa （DGKtO gene associated with hypospadias in populations of European descent. However, no variants of DGKKwere confirmed to be associated with hypospadias in a recent Han Chinese study population, likely due to the limited number of single-nucleotide polymorphisms （SNPs） included in the analysis. In this study, we aimed to address the inconsistent results and evaluate the association between DGKK and hypospadias in the Han Chinese population through a more comprehensive analysis of DGKK variants. We conducted association analyses for 17 SNPs in or downstream of DGKKwith hypospadias among 322 cases （58 mild, 113 moderate, 128 severe, and 23 unknown） and 1008 controls. Five SNPs （rs2211122, rs4554617, rs7058226, rs7063116, and rs5915254） in DGKK were significantly associated with hypospadias （P 〈 0.05）, with odds ratios （ORs） of 1.64-1.76. When only mild and moderate cases were compared to controls, 10 SNPs in DGKKwere significant （P〈 0.05）, with ORs of 1.56-2.13. No significant SNP was observed when only severe cases were compared to controls. This study successfully implicated DGKK variants in hypospadias risk among a Han Chinese population, especially for mild/moderate cases. Severe forms of hyposDadias are likely due to other genetic factors.

Turnover of diacylglycerol kinase 4 by cytoplasmic acidification induces vacuole morphological change and nuclear DNA degradation in the early stage of pear self-incompatibility response

Pear has an S-RNase-based gametophytic selfincompatibility(SI)system.Nuclear DNA degradation is a typical feature of incompatible pollen tube death,and is among the many physiological functions of vacuoles.However,the specific changes that occur in vacuoles,as well as the associated regulatory mechanism in pear SI,are currently unclear.Although research in tobacco has shown that decreased activity of diacylglycerol kinase(DGK)results in the morphological change of pollen tube vacuole,whether DGK regulates the pollen tube vacuole of tree plants and whether it occurs in SI response,is currently unclear.We found that DGK activity is essential for pear pollen tube growth,and DGK4 regulates pollen tube vacuole morphology following its high expression and deposition at the tip and shank edge of the pollen tube of pear.Specifically,incompatible S-RNase may induce cytoplasmic acidification of the pollen tube by inhibiting V-ATPase V0 domain a1 subunit gene expression as early as 30 min after treatment,when the pollen tube is still alive.Cytoplasmic acidification induced by incompatible S-RNase results in reduced DGK4 abundance and deposition,leading to morphological change of the vacuole and fragmentation of nuclear DNA,which indicates that DGK4 is a key factor in pear SI response.