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                                             process, helping cells interpret and/or   and Zhao took a closer look at
                                     8       respond to what is happening in the   various aspects of C. albicans’
                                             external world, she says.           biology. Among other findings, the
        more pseudohyphae even as the                                            scientists showed that the Sir2
        formation of true hyphae declined.   “From our perspective, what’s       protein is localized in the nucleus of
                                             important is that in either condition   C. albicans’ cells, and that removing
        More research is needed to           -- nutrient-rich or nutrient-poor -- not   the Sir2 gene from C. albicans led to
        understand why, exactly, this might   having the Sir2 gene changed the   a decrease in the activity of certain
        happen, but, “Clearly, the nutrient   balance, which implies that the signal   genes that are usually highly active
        environment changes the behavior     the Sir2 protein is transmitting is   in hyphal cells.
        of the cells,” says Rusche, PhD, UB   an important part of the equation,”
        associate professor of biological    Rusche says. “Cells are integrating a   The researchers also concluded that
        sciences.                            lot of information to ‘decide’ what form   one of the Sir2 protein’s key functions
                                             to take. Knowing more about what    -- removing an acetyl group from
        Rusche explains that different       triggers the choice could allow us to   other proteins -- is likely involved in
        cues in the environment -- such      modulate it in the future. If you can   facilitating the transition to hyphae. In
        as the availability of nutrients and   reduce Candida albicans’ ability to   experiments, disrupting this process
        temperature -- influence whether     generate the filamentous form, maybe   of deacetylation resulted in fewer true
        C. albicans takes on a yeast or      you can make it less infectious.”   hyphae being formed.
        filamentous form. Sir2, which
        belongs to a family of proteins      To learn more about how Sir2 might   “Sir2 is a protein that I’ve been
        called sirtuins, may impact this     impact hyphal formation, Rusche     studying for 20 years, so it’s been
                                                                                 at the center of my research for a
                                                                                 long time,” Rusche says. “We’ve
                                                                                 been interested in how it has
                                                                                 different functions in different
                                                                                 species. We decided it would
                                                                                 be interesting to look at the Sir2
                                                                                 protein in Candida albicans
                                                                                 because it has medical relevance,
                                                                                 and we wanted to see what our
                                                                                 knowledge about this protein can
                                                                                 help us learn about the pathogen.”

                                                                                 “I’m interested in pathogenic
                                                                                 species,” Zhao says. “The Sir2
                                                                                 protein seems to have this effect in
                                                                                 the morphological transition between
                                                                                 yeast and hyphal form. We think
                                                                                 that this transition may impact the
                                                                                 virulence of this human pathogen, so
                                                                                 that’s very important.”

                                                                                 The research was supported by a pilot
                                                                                 project award from the UB Genome,
                                                                                 Environment and Microbiome
                                                                                 Community of Excellence.

                                                                                 Story Source:
                                                                                 Materials provided by University at
                                                                                 Buffalo. Original written by Charlotte
                                                                                 Hsu. Note: Content may be edited for
                                                                                 style and length.

                                                                                 Journal Reference:
                                                                                 1. Guolei Zhao, Laura N. Rusche.
                                                                                 Genetic Analysis of Sirtuin
                                                                                 Deacetylases in Hyphal Growth of
                                                                                 Candida albicans. mSphere, 2021
               Candida albicans visualized by Gram stain and microscopy. Note the hyphae
               and chlamydospores, which are 2–4 µm in diameter.                 DOI: 10.1128/mSphere.00053-21

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