Cloning of the glyceraldehyde-3-phosphate dehydrogenase gene from Pseudozyma flocculosa and functionality of its promoter in two Pseudozyma species

Gene transfer to plants by electroporation: methods and applications

Developing gene transfer technologies enables the genetic manipulation of the living organisms more efficiently. The methods used for gene transfer fall into two main categories; natural and artificial transformation. The natural methods include the conjugation, transposition, bacterial transformation as well as phage and retroviral transductions, contain the physical methods whereas the artificial methods can physically alter and transfer genes from one to another organisms' cell using, for instance, biolistic transformation, micro- and macroinjection, and protoplast fusion etc. The artificial gene transformation can also be conducted through chemical methods which include calcium phosphate-mediated, polyethylene glycol-mediated, DEAE-Dextran, and liposome-mediated transfers. Electrical methods are also artificial ways to transfer genes that can be done by electroporation and electrofusion. Comparatively, among all the above-mentioned methods, electroporation is being widely used owing to its high efficiency and broader applicability. Electroporation is an electrical transformation method by which transient electropores are produced in the cell membranes. Based on the applications, process can be either reversible where electropores in membrane are resealable and cells preserve the vitality or irreversible where membrane is not able to reseal, and cell eventually dies. This problem can be minimized by developing numerical models to iteratively optimize the field homogeneity considering the cell size, shape, number, and electrode positions supplemented by real-time measurements. In modern biotechnology, numerical methods have been used in electrotransformation, electroporation-based inactivation, electroextraction, and electroporative biomass drying. Moreover, current applications of electroporation also point to some other uncovered potentials for various exploitations in future.

A novel glyceraldehyde-3-phosphate dehydrogenase (GAPDH) promoter for expressing transgenes in the halotolerant alga Dunaliella salina

A major challenge for efficient transgene expression in Dunaliella salina is to find strong endogenous promoters to drive the transgene expression. In the present study, a novel glyceraldehyde-3-phosphate dehydrogenase (GAPDH) promoter was cloned and used to drive expressions of the bialaphos resistance (bar) gene and of the N-terminal fragment of human canstatin (Can-N). The results showed that the bar gene was transcribed by the GAPDH promoter and integrated into the genome of the transformants of D. salina. Furthermore, the PCR identification, Southern and western blots indicated that Can-N was expressed in transgenic D. salina, demonstrating that the promoter of the D. salina GAPDH gene is suitable for driving expression of heterologous genes in transgenic D. salina.

Ustilago maydis transcript features identified through full-length cDNA analysis

Ustilago maydis is the model for investigating basidiomycete biotrophic plant pathogens. To further the annotation of its genome, 12,943 full-length cDNA sequences were used to construct databases for the promoter and untranslated regions of U. maydis genes. A subset of clones was sequenced to determine full cDNA sequences. These and the original ESTs were assembled into contigs representing 3,058, or 45%, of the predicted U. maydis genes. The new sequencing allowed the confirmation of 2,842 gene models, 690 of which contain an intron. The use of full-length cDNA clone sequences ensured that untranslated regions were physically linked to the open reading frames (ORFs), not merely aligned upstream of the start of transcription. Identified sequence features include: (1) over 500 potential short upstream ORFs, (2) 95 gene models that require further annotation, (3) one new potential ORF, (4) varying GC content in different gene regions, (5) a WebLogo motif for the start of translation, (6) the correlation of UTR length with transcript representation in cDNA libraries and with gene function categories, (7) a relationship between natural antisense transcripts and UTR length that differs from that of Saccharomyces cerevisiae, (8) a potential relationship between DNA replication and the control of transcription, and (9) new insights regarding mechanisms for the control of transcription and mRNA maturation in U. maydis.

Identification of genes potentially involved in the biocontrol activity of Pseudozyma flocculosa

Flocculosin is an antifungal cellobiose lipid linked to the biocontrol activity of Pseudozyma flocculosa and whose structure is very similar to that of ustilagic acid produced by Ustilago maydis. In this work, homologs of the U. maydis cyp1 gene, involved in the biosynthesis of ustilagic acid, were isolated and sequenced from P. flocculosa and P. fusiformata, the latter species being also known to produce ustilagic acid. Interestingly, no homologs were found in four other closely related Pseudozyma spp. from which no evidence of ustilagic acid production has ever been obtained, thus supporting the specificity of cyp1 with ustilagic acid synthesis. In addition, a homolog of the U. maydis uat1 gene involved in the acetylation of the molecule and located next to the cyp1 gene was partially sequenced from P. flocculosa. All three newly sequenced genes showed strong sequence similarity to their counterparts in U. maydis. Cyp1 expression was monitored in conditions that were either conducive or repressive to flocculosin production. Expression increased markedly (>100x) when P. flocculosa was inoculated in a growth medium conducive to flocculosin production but was rapidly downregulated in a repressive medium (in vitro) or on powdery mildew-infected cucumber leaves (in vivo). This suggests that the molecule was preferentially synthesized early in the process of searching for a growth substrate. This study provides the first identification of genes involved in the production of flocculosin, a molecule potentially associated with the biocontrol properties of P. flocculosa.

The glyceraldehyde-3-phosphate dehydrogenase gene of Moniliophthoraperniciosa, the causal agent of witches' broom disease of Theobroma cacao

This report describes the cloning, sequence and expression analysis of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene of Moniliophthora perniciosa, the most important pathogen of cocoa in Brazil. Southern blot analysis revealed the presence of a single copy of the GAPDH gene in the M. perniciosa genome (MpGAPDH). The complete MpGAPDH coding sequence contained 1,461 bp with eight introns that were conserved in the GAPDH genes of other basidiomycete species. The cis-elements in the promoter region of the MpGAPDH gene were similar to those of other basidiomycetes. Likewise, the MpGAPDH gene encoded a putative 339 amino acid protein that shared significant sequence similarity with other GAPDH proteins in fungi, plants, and metazoans. Phylogenetic analyses clustered the MPGAPDH protein with other homobasidiomycete fungi of the family Tricholomataceae. Expression analysis of the MpGAPDH gene by real-time PCR showed that this gene was more expressed (~1.3X) in the saprotrophic stage of this hemibiotrophic plant pathogen than in the biotrophic stage when grown in cacao extracts.

Identification of a minimal cre1 promoter sequence promoting glucose-dependent gene expression in the beta-lactam producer Acremonium chrysogenum

The promoter of the cre1 gene, encoding the glucose-dependent regulator CRE1 from the beta-lactam producer Acremonium chrysogenum, carries 15 putative CRE1 binding sites (BS1 to BS15). For a detailed analysis, we fused cre1 promoter deletion derivatives with the DsRed reporter gene to perform a comparative gene expression analysis. Plate assays, Northern hybridizations, and spectrofluorometric measurements of DsRed identified the minimal D4 promoter sequence that promoted glucose-dependent expression. Truncated recombinant CRE1 interacted with D4 in electromobility shift analysis and these binding studies were further extended with two oligonucleotides, carrying putative CRE1 binding sites BS14 and BS15. Surface plasmon resonance analysis was performed using BS14 and BS15, along with four derivatives containing 2 or 4 bp substitutions within BS14 and BS15, respectively. Substitutions within BS14 abolished the high affinity interaction with CRE1, while mutations in BS15 only marginally diminished the affinity with CRE1. In vivo analysis of a modified D4 sequence with substitutions in the two binding sites confirmed the in vitro binding results and still promoted glucose-dependent gene expression. Our results will contribute to the construction of versatile expression vectors carrying a minimal cre1 promoter sequence that still confers glucose-dependent induction of gene expression.