Publications

• Highly divergent methyltransferases catalyze a conserved reaction in tocopherol and plastoquinone synthesis in cyanobacteria and photosynthetic eukaryotes.

  Cheng Z., Sattler S., Maeda H., Sakuragi Y., Bryant D.A., DellaPenna D.

  Tocopherols are lipid-soluble compounds synthesized only by photosynthetic eukaryotes and oxygenic cyanobacteria. The pathway and enzymes for tocopherol synthesis are homologous in cyanobacteria and plants except for 2-methyl-6-phytyl-1,4-benzoquinone/2-methyl-6-solanyl-1,4-benzoquinone methyltran ... >> More

  Tocopherols are lipid-soluble compounds synthesized only by photosynthetic eukaryotes and oxygenic cyanobacteria. The pathway and enzymes for tocopherol synthesis are homologous in cyanobacteria and plants except for 2-methyl-6-phytyl-1,4-benzoquinone/2-methyl-6-solanyl-1,4-benzoquinone methyltransferase (MPBQ/MSBQ MT), which catalyzes a key methylation step in both tocopherol and plastoquinone (PQ) synthesis. Using a combined genomic, genetic, and biochemical approach, we isolated and characterized the VTE3 (vitamin E defective) locus, which encodes MPBQ/MSBQ MT in Arabidopsis. The phenotypes of vte3 mutants are consistent with the disruption of MPBQ/MSBQ MT activity to varying extents. The ethyl methanesulfonate-derived vte3-1 allele alters tocopherol composition but has little impact on PQ levels, whereas the null vte3-2 allele is deficient in PQ and alpha- and gamma-tocopherols. In vitro enzyme assays confirmed that VTE3 is the plant functional equivalent of the previously characterized MPBQ/MSBQ MT (Sll0418) from Synechocystis sp PCC6803, although the two proteins are highly divergent in primary sequence. Sll0418 orthologs are present in all fully sequenced cyanobacterial genomes, Chlamydomonas reinhardtii, and the diatom Thalassiosira pseudonana but absent from vascular and nonvascular plant databases. VTE3 orthologs are present in all vascular and nonvascular plant databases and in C. reinhardtii but absent from cyanobacterial genomes. Intriguingly, the only prokaryotic genomes that contain VTE3-like sequences are those of two species of archea, suggesting that, in contrast to all other enzymes of the plant tocopherol pathway, the evolutionary origin of VTE3 may have been archeal rather than cyanobacterial. In vivo analyses of vte3 mutants and the corresponding homozygous Synechocystis sp PCC6803 sll0418::aphII mutant revealed important differences in enzyme redundancy, the regulation of tocopherol synthesis, and the integration of tocopherol and PQ biosynthesis in cyanobacteria and plants. << Less

  Plant Cell 15:2343-2356(2003) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Current opinions on the functions of tocopherol based on the genetic manipulation of tocopherol biosynthesis in plants.

  Li Y., Wang Z., Sun X., Tang K.

  As a member of an important group of lipid soluble antioxidants, tocopherols play a paramount role in the daily diet of humans and animals. Recently, genes required for tocochromanol biosynthesis pathway have been identified and cloned with the help of genomics-based approaches and molecular manip ... >> More

  As a member of an important group of lipid soluble antioxidants, tocopherols play a paramount role in the daily diet of humans and animals. Recently, genes required for tocochromanol biosynthesis pathway have been identified and cloned with the help of genomics-based approaches and molecular manipulation in the model organisms: Arabidopsis thaliana and Synechocystis sp. PCC 6803. At the basis of these foundations, genetic manipulation of tocochromanol biosynthesis pathway can give rise to strategies that enhance the level of tocochromanol content or convert the constitution of tocochromanol. In addition, genetic manipulations of the tocochromanol biosynthesis pathway provide help for the study of the function of tocopherol in plant systems. The present article summarizes recent advances and pays special attention to the functions of tocopherol in plants. The roles of tocopherol in the network of reactive oxygen species, antioxidants and phytohormones to maintain redox homeostasis and the functions of tocopherol as a signal molecule in chloroplast-to-nucleus signaling to regulate carbohydrate metabolism are also discussed. << Less

  J Integr Plant Biol 50:1057-1069(2008) [PubMed] [EuropePMC]