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Author: search.filters.author.Kamthan, MohanSubject: search.filters.subject.Candida albicans

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    Mapping of functional domains and characterization of the transcription factor Cph1 that mediate morphogenesis in Candida albicans
    (Elsevier B.V., 2015) Maiti, Protiti; Ghorai, Priyanka; Ghosh, Sumit; Kamthan, Mohan; Tyagi, Rakesh Kumar; Datta, Asis
    Cph1, a transcription factor of the Mitogen Activated Protein (MAP) kinase pathway, regulates morphogenesis in human fungal pathogen Candida albicans. Here, by following a systemic deletion approach, we have identified functional domains and motifs of Cph1 that are involved in transcription factor activity and cellular morphogenesis. We found that the N-terminal homeodomain is essential for the DNA binding activity; however, C-terminal domain and polyglutamine motif (PQ) are indispensable for the transcriptional activation function. Complementation analysis of the cph1Δ null mutant using various deletion derivatives revealed functional significance of the N- and C-terminal domains and PQ motif in filamentation process, chlamydospore formation and sensitivity to the cell wall interfering compounds. Genome-wide identification of the Cph1 binding site and quantitative RT-PCR transcript analysis in cph1Δ null mutant revealed that a number of genes which are associated with the filamentous growth, maintaining cell wall organization and mitochondrial function, and the genes of the pH response pathway are the transcriptional targets of Cph1. The data also suggest that Cph1 may function as a positive or negative regulator depending on the morphological state and physiological conditions. Moreover, differential expression of the upstream MAP kinase pathway genes in wild type and cph1Δ null mutant indicated the existence of a feedback regulation.
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    Characterization of a putative spindle assembly checkpoint kinase Mps1, suggests its involvement in cell division, morphogenesis and oxidative stress tolerance in Candida albicans
    (PLOS, 2014) Kamthan, Mohan; Nalla, Vijaya Kumar; Ruhela, Deepa; Kamthan, Ayushi; Maiti, Protiti; Datta, Asis
    In Saccharomyces cerevisiae MPS1 is one of the major protein kinase that governs the spindle checkpoint pathway. The S. cerevisiae structural homolog of opportunistic pathogen Candida albicans CaMPS1, is indispensable for the cell viability. The essentiality of Mps1 was confirmed by Homozygote Trisome test. To determine its biological function in this pathogen conditional mutant was generated through regulatable MET3 promoter. Examination of heterozygous and conditional (+Met/Cys) mps1 mutants revealed a mitosis specific arrest phenotype, where mutants showed large buds with undivided nuclei. Flowcytometry analysis revealed abnormal ploidy levels in mps1 mutant. In presence of anti-microtubule drug Nocodazole, mps1 mutant showed a dramatic loss of viability suggesting a role of Mps1 in Spindle Assembly Checkpoint (SAC) activation. These mutants were also defective in microtubule organization. Moreover, heterozygous mutant showed defective in-vitro yeast to hyphae morphological transition. Growth defect in heterozygous mutant suggest haploinsufficiency of this gene. qRT PCR analysis showed around 3 fold upregulation of MPS1 in presence of serum. This expression of MPS1 is dependent on Efg1 and is independent of other hyphal regulators like Ras1 and Tpk2. Furthermore, mps1 mutants were also sensitive to oxidative stress. Heterozygous mps1 mutant did not undergo morphological transition and showed 5-Fold reduction in colony forming units in response to macrophage. Thus, the vital checkpoint kinase, Mps1 besides cell division also has a role in morphogenesis and oxidative stress tolerance, in this pathogenic fungus.