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Category: Fungi and Fungal Pathogenesis; Clinical Microbiology
Cool Tools 5: The Candida albicans ORFeome Project, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817176/9781555815394_Chap34-1.gif /docserver/preview/fulltext/10.1128/9781555817176/9781555815394_Chap34-2.gifAbstract:
This chapter presents the strategy developed to generate a Candida albicans ORFeome collection in a versatile Gateway vector, which allows the transfer of the cloned genes into a variety of C. albicans Gateway-compatible expression vectors. The development of collections of over-expression strains is facilitated by the pre-establishment of a complete set of cloned open reading frames (ORFs), or ORFeome. Importantly, ORFeomes represent useful resources for the implementation of other approaches used to elucidate gene function apart from gene deletion or overexpression. Individual characterization of mutants on the genome-wide scale can be slow and laborious. In this respect, signature-tagged mutagenesis (STM) provides an attractive alternative. In STM, each mutant is tagged with a different DNA sequence, allowing all tags to be amplified from the DNA of mixed populations of mutants in a single PCR. In the C. albicans ORFeome, the start codon of the 6,205 ORFs has been included, whereas the stop codon has been excluded to allow insertion of C-terminal tags. The authors have favored C-terminal tagging since tags at the amino termini may possibly interfere with targeting of proteins to the secretory pathway. A panel of libraries of strains expressing tagged proteins should facilitate the systematic execution of high-throughput biochemical and microscopic assays of the C. albicans proteome. The construction of the ORFeome could pave the way to the generation of the C. albicans promoterome (library of gene promoters) in order to better characterize expression profiles.
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Workflow of the C. albicans ORFeome project. Shown is the overall scheme for high-throughput recombinational cloning of the C. albicans ORFs using the Gateway system. Quality control is monitored and documented using PCR and DNA sequencing. The main steps are briefly summarized on the right in the order they are carried out. doi:10.1128/9781555817176.ch34.f1
Plasmids used in this work. (A) Schematic map of the CIp10-TETp-GTW destination vector used for overexpression of Candida albicans ORFs. ORFs cloned in a Gateway donor vector can be transferred through Gateway-mediated recombination at attR1 and attR2 of CIp10-TETp-GTW overexpression vectors. The URA3 gene is used for selection of C. albicans transformants. Derivatives of these overexpression vectors can be targeted to the C. albicans RPS1 locus when linearized with StuI or I-SceI. Expression of the cloned ORFs is achieved when C. albicans cells are grown in the presence of doxycycline, which binds to the tetracycline-dependent transactivator rtTA, allowing transcriptional activation at the Tetp promoter. Each expression plasmid is tagged with a unique 12-bp barcode, enabling growth phenotypes of individual strains to be analyzed in parallel. (B) Structure of the tetracycline-dependent transactivator cassette contained in plasmid pNIMX. Unique restriction sites to excise the entire cassette are indicated. P TDH3 , basal promoter of CaTDH3; SAT1, nourseothricin resistance gene; cartetR-CaGAL4AD, Candida albicans-adapted reverse tetracycline-dependent transactivator cartTA gene. doi:10.1128/9781555817176.ch34.f2