Cloning and Enzymatic Activity Analysis of the Malonyl-CoA:acyl Carrier Protein Transacylase in <i>Brassica napus</i>Cultivars with Different Oil Content

The full-length genomic DNA of MCAT (Malonyl-CoA:acyl carrier protein transacylase) in Brassica napus was cloned. BnMCAT shares very high identity with AtMCAT in gene sequence and gene structure. A multiple alignment of the protein sequence showed that BnMCAT shares high identity with other MCATs from E. coli and plants. BnMCAT was expressed in all tissues, such as roots, stems, leaves, flowers, and seeds, and no significant differences in the expression level were found in different embryo stages after pollination. According to an in vitro relative activity analysis, purified recombinant BnMCAT expressed in E. coli had transacylase activity. Although the relative activities of BnMCAT in crude extracts isolated from different staged embryos were similar and showed little variation, a higher relative activity was found in a crude extract isolated from embryos in comparison to leaves. Different relative activities of BnMCAT in crude extracts isolated from cultivars with different oil content were also found, suggesting that the activity of BnMCAT might be a decisive factor for a high oil content. Together, these results showed that BnMCAT is an important enzyme in the FAS system and indicate that BnMCAT might be a new target enzyme for future crop improvement through genetic engineering.

A Novel Method for Production of 3-Hydroxydecanoic Acid by Recombinant Escherichia coli and Pseudomonas putida

3-hydroxydecanoic acid (3HD) is an interesting intermediate for chemical synthesis of many valuable compounds. A novel method to produce 3HD by recombinant bacteria was constructed in Escherichia coli HB101 and Pseudomonas putida GPpl04, respectively. Simultaneous expression of both phaG encoding (R)-3-hydroxydecanoyl-ACP:CoA transacylase and tesB encoding thioesteraseⅡin E. coli HB101 increased 3HD production approximate 1.7-folds compared with the expression of phaG gene alone under identical conditions. In addition, when the tesB gene was introduced into the strain, the polyhydroxyalkanoate synthase negative strain P. putida GPpl04 produced extracellular 3HD. Thus, a novel pathway to produce 3HD by recombinant Pseudomonas was constructed. It was also found that the ratio of carbon source to nitrogen source affected the production of 3HD by recombinant P. putida harboring tesB gene. Nitrogen limitation seemed to promote the extracellular 3HD production.

N6-methyladenosine-modified DBT alleviates lipid accumulation and inhibits tumor progression in clear cell renal cell carcinoma through the ANXA2/YAP axis-regulated Hippo pathway

Background:The mechanism of metabolism reprogramming is an unsolved problem in clear cell renal cell carcinoma(ccRCC).Recently,it was discovered that the Hippo pathway altered tumor metabolism and promoted tumor progression.Thus,this study aimed at identifying key regulators of metabolism reprogramming and the Hippo pathway in ccRCC and pinpointing potential therapeutic targets for ccRCC patients.Methods:Hippo-related gene sets and metabolic gene sets were used to screen potential regulators of the Hippo pathway in ccRCC.Public databases and samples from patients were applied to investigate the association of dihydrolipoamide branched chain transacylase E2(DBT)with ccRCC and Hippo signaling.The role of DBT was confirmed by gain or loss of function assays in vitro and in vivo.Mechanistic results were yielded by luciferase reporter assay,immunoprecipitation,mass spectroscopy,and mutational studies.Results:DBT was confirmed as a Hippo-related marker with significant prognostic predictive value,and its downregulationwas caused bymethyltransferaselike-3(METTL3)-mediated N6-methyladenosine(m6A)modification in ccRCC.Functional studies specified DBT as a tumor suppressor for inhibiting tumor progression and correcting the lipid metabolism disorder in ccRCC.Mechanistic findings revealed that annexin A2(ANXA2)interacted with the lipoyl-binding domain of DBT to activate Hippo signaling which led to decreased nuclear localization of yes1-associated transcriptional regulator(YAP)and transcriptional repression of lipogenic genes.Conclusions:This study demonstrated a tumor-suppressive role for the DBT/ANXA2/YAP axis-regulated Hippo signaling and suggested DBT as a potential target for pharmaceutical intervention in ccRCC.