Sequence of a cDNA from Oryza sativa (L.) encoding the pyruvate decarboxylase 1 gene

Production and phenotypic analysis of rice transgenics with altered levels of pyruvate decarboxylase and alcohol dehydrogenase proteins

Pyruvate decarboxylase (Pdc) and alcohol dehydrogenase (Adh) enzymes are responsible for the operation of ethanolic fermentation pathway that appears to correlate to an extent with anoxia tolerance in plants. This study was undertaken with the objective of (a) analysing the rice pdc gene family and (b) altering the efficacy of the ethanolic fermentation process, through production of transgenic rice plants over- and under-expressing pyruvate decarboxylase (employing Ospdc1 gene from rice) as well as over-expressing alcohol dehydrogenase (employing Ghadh2 gene from cotton) proteins. Correlations noted in this study between the pattern of expression of the Pdc alpha-subunit and Ospdc2 transcript as well as between the Pdc beta-subunit and Ospdc1 transcript suggest the possibility that alpha-subunit is encoded by Ospdc2 and that beta-subunit is encoded by Ospdc1. The fact that levels of Pdc beta-subunit were particularly high in pUH-sPdc1 (plasmid construct designed for over-expression of Ospdc1) seedlings while levels of beta-subunit levels were negligible or lower in pUH-asPdc1 (plasmid construct designed for under-expression of Ospdc1) seedlings also support these observations. Transgenics raised for over-expression of Pdc and Adh and under-expression of Pdc were confirmed for the transgene presence and effects by PCR, Southern blotting, Northern blotting, Western blotting and isozyme assays. Pdc and Adh over-expressing rice transgenics at early seedling stage under unstressed control growth conditions showed slight, consistent advantage in root vigour as compared to that of wild-type seedlings.

Fermentative metabolism in grape berries: isolation and characterization of pyruvate decarboxylase cDNA and analysis of its expression throughout berry development

The involvement of pyruvate decarboxylase (PDC) in the control of alcohol production during ripening of fruit tissues under aerobic conditions has been only partially studied. Enzymological studies showed a significant increase in PDC activity during the ripening of oranges and pears, concurrently with the induction of ethanol production. In tomato, on the other hand, the induction of ethanol production and ADH gene expression after the onset of ripening was not accompanied by induction of PDC activity. The isolation of PDC cDNA from fruits has not yet been reported, nor has its expression pattern during fruit development. We report here the isolation of a cDNA clone encoding for a grape PDC and the characterization of its expression throughout berry development. The pattern of PDC gene expression throughout berry development, combined with earlier findings on constitutive PDC activity in the berry, may suggest that PDC is not the limiting factor for the production of ethanol in the berry, which is induced only after the onset of berry ripening. Alternatively, the induction of ADH gene expression, which occurs only after the onset of ripening in both tomatoes and grape berries, may serve as a regulator of ethanol production in response to a ripening-related cue.

Application of alpha-keto acid decarboxylases in biotransformations

The advantages of using enzymes in the synthesis of organic compounds relate to their versatility, high reaction rates, and regio- and stereospecificity and the relatively mild reaction conditions involved. Stereospecificity is especially important in the synthesis of bioactive molecules, as only one of the enantiomeric forms usually manifests bioactivity, whereas the other is often toxic. Although enzymes which catalyze asymmetric carbon-carbon bond formation are of great importance in bioorganic chemistry, only a few examples are known for thiamin diphosphate (ThDP)-dependent enzymes, whereas transformations using e.g. aldolases, lipases and lyases are well documented already. The present review surveys recent work on the application of pyruvate decarboxylase and benzoylformate decarboxylase in organic synthesis. These enzymes catalyze the synthesis of chiral alpha-hydroxy ketones which are versatile building blocks for organic and pharmaceutical chemistry. Besides the substrate spectra of both enzymes amino acid residues relevant for substrate specificity and enantioselectivity of pyruvate decarboxylase have been investigated by site-directed mutagenesis.

Differential induction of pyruvate decarboxylase subunits and transcripts in anoxic rice seedlings

In 2-d-old rice (Oryza sativa L.) seedlings subjected to anoxic stress, pyruvate decarboxylase (PDC) activity increased 9-fold during a 168-h period. A polyclonal PDC antiserum that recognized alpha- and beta-subunits was used to quantify PDC protein by an enzyme-linked immunosorbant assay and showed a 5.6-fold increase, suggesting that the anoxically induced enzyme has a higher specific activity than the PDC isoform present under normoxia. Immunoblot analysis showed that levels of both PDC subunits were induced by anoxia. Immunoprecipitation of proteins labeled in vivo during anoxic treatment demonstrated that the alpha-subunit was preferentially synthesized at the onset of anoxia. Two partial cDNAs, including a novel sequence, were cloned from a cDNA library made from seedlings subjected to anoxia for 6 h. Gene-specific probes used to quantify northern blots showed that two or three PDC mRNAs are differentially induced by anoxia in rice seedlings. Immunoprecipitation of in vitro translation products of mRNAs isolated a different times of anoxic treatment confirmed this findings Our results suggest that anoxic induction of rice PDC involves transcriptional and posttranscriptional regulation of gene expression as well as differences in enzyme characteristics.

Characterization of pyruvate decarboxylase genes from rice

The pdc1 gene encoding pyruvate decarboxylase has been isolated and sequenced from an IR54 rice genomic library. In contrast to a previously isolated intron-less rice genomic pdc, pRgpdc3, this gene contains five intervening introns in the coding region and corresponds to a cDNA clone, pRcpdc1, isolated from an IR54-cDNA library constructed from anaerobically-induced mRNAs. Comparison of the deduced amino acid sequence of this gene with that of the rice pdc2 and pdc3 showed 88% and 89% similarity, and 78% and 79% identity, respectively. Southern blots indicated that more than three genes constitute the pdc gene family in rice. pdc1 is highly inducible under anaerobic conditions. Rice pdc2 is also inducible by anoxia but to a much lesser extent than pdc1.

Pyruvate decarboxylase from Pisum sativum. Properties, nucleotide and amino acid sequences

To study the molecular structure and function of pyruvate decarboxylase (PDC) from plants the protein was isolated from pea seeds and partially characterised. The active enzyme which occurs in the form of higher oligomers consists of two different subunits appearing in SDS/PAGE and mass spectroscopy experiments. For further experiments, like X-ray crystallography, it was necessary to elucidate the protein sequence. Partial cDNA clones encoding pyruvate decarboxylase from seeds of Pisum sativum cv. Miko have been obtained by means of polymerase chain reaction techniques. The first sequences were found using degenerate oligonucleotide primers designated according to conserved amino acid sequences of known pyruvate decarboxylases. The missing parts of one cDNA were amplified applying the 3'- and 5'-rapid amplification of cDNA ends systems. The amino acid sequence deduced from the entire cDNA sequence displays strong similarity to pyruvate decarboxylases from other organisms, especially from plants. A molecular mass of 64 kDa was calculated for this protein correlating with estimations for the smaller subunit of the oligomeric enzyme. The PCR experiments led to at least three different clones representing the middle part of the PDC cDNA indicating the existence of three isozymes. Two of these isoforms could be confirmed on the protein level by sequencing tryptic peptides. Only anaerobically treated roots showed a positive signal for PDC mRNA in Northern analysis although the cDNA from imbibed seeds was successfully used for PCR.