Characterization of RNA Helicase Genes in Ustilago maydis Reveals Links to Stress Response and Teliospore Dormancy

Fungi produce dormant structures that are responsible for protection during adverse environmental conditions and dispersal (disease spread). <i>Ustilago maydis</i>, a basidiomycete plant pathogen, is a model for understanding the molecular mechanisms of teliospore dormancy and germination. Dormant teliospores store components required for germination including mRNAs which may be stored as dsRNAs. RNA helicases are conserved enzymes that function to modulate, bind, and unwind RNA duplexes, and can displace other proteins. We hypothesize that RNA helicases function during teliospore dormancy to stabilize and/or modulate stored mRNAs. We identified the <i>U. maydis udbp3</i> and <i>uded1</i> as encoding RNA helicases of interest as they are upregulated in the dormant teliospore and decrease during germination. Experimental results suggest that <i>udbp3</i> may function as a negative regulator of osmotic stress-responsive genes and that <i>uded1</i> modulates stress response by repressing translation. The altered expression of <i>uded1</i> also results in slow growth, polarized growth, and the formation of dsRNA. Together, the data support a role for both helicases modulating gene expression, in response to stress, leading to teliospore dormancy and also modulating responses for teliospore germination. Increasing our molecular understanding of these processes will aid in developing novel strategies to mitigate disease spread.