Comparative homology modeling of pyruvate dehydrogenase kinase isozymes from Xenopus tropicalis reveals structural basis for their subfunctionalization

Antisense knockdown of pyruvate dehydrogenase kinase promotes the neutral lipid accumulation in the diatom Phaeodactylum tricornutum

Background

Microalgae have been an emerging biofuel resource; however, the germplasm improvement has been slow due to the lack of molecular tools. Pyruvate dehydrogenase kinase (PDK) deactivates the pyruvate dehydrogenase complex (PDC) which catalyzes the oxidative decarboxylation of pyruvate. Acetyl-CoA production via PDC is important in plant tissues that are active in fatty acid synthesis.

Results

A 1261-bp cDNA of a putative PDK gene (PtPDK) was cloned from a diatom Phaeodactylum tricornutum, and PtPDK antisense knockdown transgenic diatoms were generated. Both PtPDK transcript abundance and enzyme activity were reduced significantly due to antisense knockdown of PtPDK. Neutral lipid content of transgenic diatom cells increased up to 82% as determined by Nile red staining, and fatty acid composition was not altered. Transgenic cells showed slightly lower growth rate but similar cell size with the wild type, hence retaining similar biomass productivity.

Conclusions

This work first obtained a successful engineered diatom regulating a key gene involved in lipid metabolism. Our findings also provide powerful indications in enhancing microalgal lipid production by metabolic engineering for biofuel industry.

Antisense knockdown of pyruvate dehydrogenase kinase promotes the neutral lipid accumulation in the diatom Phaeodactylum tricornutum

BACKGROUND

Microalgae have been an emerging biofuel resource; however, the germplasm improvement has been slow due to the lack of molecular tools. Pyruvate dehydrogenase kinase (PDK) deactivates the pyruvate dehydrogenase complex (PDC) which catalyzes the oxidative decarboxylation of pyruvate. Acetyl-CoA production via PDC is important in plant tissues that are active in fatty acid synthesis.

RESULTS

A 1261-bp cDNA of a putative PDK gene (PtPDK) was cloned from a diatom Phaeodactylum tricornutum, and PtPDK antisense knockdown transgenic diatoms were generated. Both PtPDK transcript abundance and enzyme activity were reduced significantly due to antisense knockdown of PtPDK. Neutral lipid content of transgenic diatom cells increased up to 82% as determined by Nile red staining, and fatty acid composition was not altered. Transgenic cells showed slightly lower growth rate but similar cell size with the wild type, hence retaining similar biomass productivity.

CONCLUSIONS

This work first obtained a successful engineered diatom regulating a key gene involved in lipid metabolism. Our findings also provide powerful indications in enhancing microalgal lipid production by metabolic engineering for biofuel industry.

Pyruvate Dehydrogenase Kinases in the Nervous System: Their Principal Functions in Neuronal-glial Metabolic Interaction and Neuro-metabolic Disorders

Metabolism is involved directly or indirectly in all processes conducted in living cells. The brain, popularly viewed as a neuronal-glial complex, gets most of its energy from the oxygen-dependent metabolism of glucose, and the mitochondrial pyruvate dehydrogenase complex (PDC) plays a key regulatory role during the oxidation of glucose. Pyruvate dehydrogenase kinase (also called PDC kinase or PDK) is a kinase that regulates glucose metabolism by switching off PDC. Four isoforms of PDKs with tissue specific activities have been identified. The metabolisms of neurons and glial cells, especially, those of astroglial cells, are interrelated, and these cells function in an integrated fashion. The energetic coupling between neuronal and astroglial cells is essential to meet the energy requirements of the brain in an efficient way. Accumulating evidence suggests that alterations in the PDKs and/or neuron-astroglia metabolic interactions are associated with the development of several neurological disorders. Here, the authors review the results of recent research efforts that have shed light on the functions of PDKs in the nervous system, particularly on neuron-glia metabolic interactions and neuro-metabolic disorders.

Development of Xenopus resource centers: the National Xenopus Resource and the European Xenopus Resource Center

Xenopus is an essential vertebrate model system for biomedical research that has contributed to important discoveries in many disciplines, including cell biology, molecular biology, physiology, developmental biology, and neurobiology. However, unlike other model systems no central repository/stock center for Xenopus had been established until recently. Similar to mouse, zebrafish, and fly communities, which have established stock centers, Xenopus researchers need to maintain and distribute rapidly growing numbers of inbred, mutant, and transgenic frog strains, along with DNA and protein resources, and individual laboratories struggle to accomplish this efficiently. In the last 5 years, two resource centers were founded to address this need: the European Xenopus Resource Center (EXRC) at the University of Portsmouth in England, and the National Xenopus Resource (NXR) at the Marine Biological Laboratory in Woods Hole, MA. These two centers work together to provide resources and support to the Xenopus research community. The EXRC and NXR serve as stock centers and acquire, produce, maintain and distribute mutant, inbred and transgenic Xenopus laevis and Xenopus tropicalis lines. Independently, the EXRC is a repository for Xenopus cDNAs, fosmids, and antibodies; it also provides oocytes and wild-type frogs within the United Kingdom. The NXR will complement these services by providing research training and promoting intellectual interchange through hosting mini-courses and workshops and offering space for researchers to perform short-term projects at the Marine Biological Laboratory. Together the EXRC and NXR will enable researchers to improve productivity by providing resources and expertise to all levels, from graduate students to experienced PIs. These two centers will also enable investigators that use other animal systems to take advantage of Xenopus' unique experimental features to complement their studies.