Lipid and phenolic metabolism are important for pollen exine formation. In Arabidopsis, polyketide synthases （PKSs） are essential for both sporopollenin biosynthesis and exine formation. Here, we characterized the r...Lipid and phenolic metabolism are important for pollen exine formation. In Arabidopsis, polyketide synthases （PKSs） are essential for both sporopollenin biosynthesis and exine formation. Here, we characterized the role of a polyketide synthase （OsPKS2） in male reproduction of rice （Oryza sativa）. Recombinant OsPKS2 catalyzed the condensation of fatty acyl-CoA with malonyl- CoA to generate triketide and tetraketide α-pyrones, the main components of pollen exine. Indeed, the ospks2 mutant had defective exine patterning and was male sterile. However, the mutant showed no significant reduction in sporopollenin accumulation. Compared with the WT （wild type）, ospks2 displayed unconfined and amorphous tectum and nexine layers in the exine, and less organized Ubisch bodies. Like the pksb/lap5 mutant of the Arabidopsis ortholog, ospks2 showed broad alterations in the profiles of anther-related phenolic compounds. However, unlike pksb/laps, in which most detected phenolics were substantially decreased, ospks2 accumu- lated higher levels of phenolics. Based on these results and our observation that OsPKS2 is unable to fully restore the exine defects in the pksb/laps, we propose that PKS proteins have functionally diversified during evolution. Collectively, our results suggest that PKSs represent a conserved and diversified biochemical pathway for anther and pollen development in higher plants.展开更多
AIM: To provide further insight into the characterization of mucosa-associated Escherichia coli (E. coli) isolated from the colonic mucosa of cancer patients.
Seven new aromatic polyketides, communols A-G （1-7）, were isolated and identified from the fermentation broth of Penicillium commune 518, a marine-derived fungus associated with the Gorgonian, Muricella abnormalis. ...Seven new aromatic polyketides, communols A-G （1-7）, were isolated and identified from the fermentation broth of Penicillium commune 518, a marine-derived fungus associated with the Gorgonian, Muricella abnormalis. The new structures of 1-7 were determined by spectroscopic analysis and X-ray single crystal diffraction. Among them, communol D （4） was the first example of a naturally occurring aromatic polyketide with a sulfoxide group from marine thngi. Compounds 1, 6, and 7 all showed moderate antimicrobial activities against Escherichia coli and Enterobacter aerogenes with MIC values of 4.1/16.4, 6.4/25.8, and 23.8/23.8μmoloL^-1, respectively.展开更多
Chaetomium globosum is one of the most common fungi in nature. It is best known for producing chaetoglobosins; however, the molecular basis of chaetoglobosin biosynthesis is poorly understood in this fungus. In this s...Chaetomium globosum is one of the most common fungi in nature. It is best known for producing chaetoglobosins; however, the molecular basis of chaetoglobosin biosynthesis is poorly understood in this fungus. In this study, we utilized RNA inter- ference （RNAi） to characterize a polyketide synthase gene, pks-1, in C. globosum that is involved in the production of chaeto- globosin A. When pks-1 was knocked down by RNAi, the production of chaetoglobosin A dramatically decreased. Knock-down mutants also displayed a pigment-deficient phenotype. These results suggest that the two polyketides, melanin and chaetoglobosin, are likely to share common biosynthetic steps. Most importantly, we found that pks-I also plays a critical role in sporulation. The silenced mutants ofpks-1 lost the ability to produce spores. We propose that polyketides may modulate cellular development via an unidentified action. We also suggest that C. globosum pks-1 is unique because of its triple role in melanin formation, chaetoglobosin biosynthesis and sporulation. This work may shed light on chaetoglobosin biosynthesis and indicates a relationship between secondary metabolism and fungal morphogenesis.展开更多
The bacterial trialkyl-substituted aromatic polyketides are structurally featured with the unusual aromatic core in the middle of polyketide chain such as TM-123(1),veramycin A(2),NFAT-133(3)and benwamycin I(4),which ...The bacterial trialkyl-substituted aromatic polyketides are structurally featured with the unusual aromatic core in the middle of polyketide chain such as TM-123(1),veramycin A(2),NFAT-133(3)and benwamycin I(4),which were discovered from Streptomyces species and demonstrated with antidiabetic and immunosuppressant activities.Though the biosynthetic pathway of 1-3 was reported as a type I polyketide synthase(PKS),the PKS assembly line was interpreted inconsistently,and it remains a mystery how the compound 3 was generated.Herein,the PKS assembly logic of 1-4 was revised by site-mutagenetic analysis of the PKS dehydratase domains.Based on gene deletion and complementation,the putative P450 monooxygenase nftE1 and metallo-beta-lactamase(MBL)fold hydrolase nftF1 were verified as essential genes for the biosynthesis of 1-4.The absence of nftE1 led to abolishment of 1-4 and accumulation of new products(5-8).Structural elucidation reveals 5-8 as the non-aromatic analogs of 1,suggesting the NftE1-catalyzed aromatic core formation.Deletion of nftF1 resulted in disappearance of 3 and 4 with the compounds 1 and 2 unaffected.As a rare MBL-fold hydrolase from type I PKSs,NftF1 potentially generates the compound 3 through two strategies:catalyze premature chain-offloading as a trans-acting thioesterase or hydrolyze the lactone-bond of compound 1 as an esterase.展开更多
基金supported by funds from the National Key Research and Development Program of China(No.2016YFD0101107)the National Key Basic Research Developments Program of the Ministry of Science and Technology of China(No.2013CB126902)+1 种基金the National Natural Science Foundation of China(No.31322040,31670309)the Innovative Research Team of the Ministry of Education and the 111 Project(No.B14016)
文摘Lipid and phenolic metabolism are important for pollen exine formation. In Arabidopsis, polyketide synthases （PKSs） are essential for both sporopollenin biosynthesis and exine formation. Here, we characterized the role of a polyketide synthase （OsPKS2） in male reproduction of rice （Oryza sativa）. Recombinant OsPKS2 catalyzed the condensation of fatty acyl-CoA with malonyl- CoA to generate triketide and tetraketide α-pyrones, the main components of pollen exine. Indeed, the ospks2 mutant had defective exine patterning and was male sterile. However, the mutant showed no significant reduction in sporopollenin accumulation. Compared with the WT （wild type）, ospks2 displayed unconfined and amorphous tectum and nexine layers in the exine, and less organized Ubisch bodies. Like the pksb/lap5 mutant of the Arabidopsis ortholog, ospks2 showed broad alterations in the profiles of anther-related phenolic compounds. However, unlike pksb/laps, in which most detected phenolics were substantially decreased, ospks2 accumu- lated higher levels of phenolics. Based on these results and our observation that OsPKS2 is unable to fully restore the exine defects in the pksb/laps, we propose that PKS proteins have functionally diversified during evolution. Collectively, our results suggest that PKSs represent a conserved and diversified biochemical pathway for anther and pollen development in higher plants.
基金Supported by Ministère de l’Enseignement supérieur et de la Recherche,Inserm and Universitéd’Auvergne(UMR1071),INRA(USC-2018)Grants from the Association F.Aupetit(AFA)and Ligue contre le cancer
文摘AIM: To provide further insight into the characterization of mucosa-associated Escherichia coli (E. coli) isolated from the colonic mucosa of cancer patients.
文摘Seven new aromatic polyketides, communols A-G （1-7）, were isolated and identified from the fermentation broth of Penicillium commune 518, a marine-derived fungus associated with the Gorgonian, Muricella abnormalis. The new structures of 1-7 were determined by spectroscopic analysis and X-ray single crystal diffraction. Among them, communol D （4） was the first example of a naturally occurring aromatic polyketide with a sulfoxide group from marine thngi. Compounds 1, 6, and 7 all showed moderate antimicrobial activities against Escherichia coli and Enterobacter aerogenes with MIC values of 4.1/16.4, 6.4/25.8, and 23.8/23.8μmoloL^-1, respectively.
基金the National Natural Science Foundation of China (Grant No. 30970084)the National Basic Research Program of China (Grant No. 2007CB707801)
文摘Chaetomium globosum is one of the most common fungi in nature. It is best known for producing chaetoglobosins; however, the molecular basis of chaetoglobosin biosynthesis is poorly understood in this fungus. In this study, we utilized RNA inter- ference （RNAi） to characterize a polyketide synthase gene, pks-1, in C. globosum that is involved in the production of chaeto- globosin A. When pks-1 was knocked down by RNAi, the production of chaetoglobosin A dramatically decreased. Knock-down mutants also displayed a pigment-deficient phenotype. These results suggest that the two polyketides, melanin and chaetoglobosin, are likely to share common biosynthetic steps. Most importantly, we found that pks-I also plays a critical role in sporulation. The silenced mutants ofpks-1 lost the ability to produce spores. We propose that polyketides may modulate cellular development via an unidentified action. We also suggest that C. globosum pks-1 is unique because of its triple role in melanin formation, chaetoglobosin biosynthesis and sporulation. This work may shed light on chaetoglobosin biosynthesis and indicates a relationship between secondary metabolism and fungal morphogenesis.
基金the National Natural Science Foundation of China(Nos.32070070,32211530074 and 31929001)the innovative research team of high-level local universities in Shanghai.H.D.thanks Royal Society-NSFC international exchange grant(IEC\NSFC\211349).
文摘The bacterial trialkyl-substituted aromatic polyketides are structurally featured with the unusual aromatic core in the middle of polyketide chain such as TM-123(1),veramycin A(2),NFAT-133(3)and benwamycin I(4),which were discovered from Streptomyces species and demonstrated with antidiabetic and immunosuppressant activities.Though the biosynthetic pathway of 1-3 was reported as a type I polyketide synthase(PKS),the PKS assembly line was interpreted inconsistently,and it remains a mystery how the compound 3 was generated.Herein,the PKS assembly logic of 1-4 was revised by site-mutagenetic analysis of the PKS dehydratase domains.Based on gene deletion and complementation,the putative P450 monooxygenase nftE1 and metallo-beta-lactamase(MBL)fold hydrolase nftF1 were verified as essential genes for the biosynthesis of 1-4.The absence of nftE1 led to abolishment of 1-4 and accumulation of new products(5-8).Structural elucidation reveals 5-8 as the non-aromatic analogs of 1,suggesting the NftE1-catalyzed aromatic core formation.Deletion of nftF1 resulted in disappearance of 3 and 4 with the compounds 1 and 2 unaffected.As a rare MBL-fold hydrolase from type I PKSs,NftF1 potentially generates the compound 3 through two strategies:catalyze premature chain-offloading as a trans-acting thioesterase or hydrolyze the lactone-bond of compound 1 as an esterase.
