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Fungal pathogens pose a global threat to human health, with Candida albicans among the leading killers. Systematic analysis of essential genes provides a powerful strategy to discover potential antifungal targets. Here, we build a machine learning model to generate genome-wide gene essentiality predictions for C. albicans and expand the largest functional genomics resource in this pathogen (the GRACE collection) by 866 genes. Using this model and chemogenomic analyses, we define the function of three uncharacterized essential genes with roles in kinetochore function, mitochondrial integrity, and translation, and identify the glutaminyl-tRNA synthetase Gln4 as the target of N-pyrimidinyl-β-thiophenylacrylamide (NP-BTA), an antifungal compound.

SUMMARY Morphological plasticity is a key virulence trait for many fungal pathogens. For the opportunistic fungal pathogen Candida albicans , transitions among yeast, pseudohyphal, and hyphal forms are critical for virulence, because the morphotypes play distinct roles in the infection process. C. albicans morphogenesis is induced in response to many host-relevant conditions and is regulated by complex signaling pathways and cellular processes. Perturbation of either cell-cycle progression or protein homeostasis induces C. albicans filamentation, demonstrating that these processes play a key role in morphogenetic control. Regulators such as cyclin-dependent kinases, checkpoint proteins, the proteasome, the heat shock protein Hsp90, and the heat shock transcription factor Hsf1 all influence morphogenesis, often through interconnected effects on the cell cycle and proteostasis. This review highlights the major cell-cycle and proteostasis regulators that modulate morphogenesis and discusses how these two processes intersect to regulate this key virulence trait.

1The picture emerging from the rapidly growing literature on host-associated micro-2 biota is that host traits and fitness often depend on complex and interactive effects 3 of host genotype, microbial interactions, and abiotic environment. However, testing 4 these main and interactive effects typically requires large, multi-factorial experiments 5 and thus remains challenging in many systems. Furthermore, most studies of plant 6 microbiomes focus on terrestrial hosts and microbes. Aquatic habitats may confer 7 unique properties to plant micriobiomes. We grew different populations of duck-8 weed (Lemna minor ), a floating aquatic plant of increasing popularity in freshwater 9 phytoremediation, in three microbial treatments (adding no, "home", or "away" 10 microbes) at two levels of zinc, a common water contaminant in urban areas. Thus, 11 we simultaneously manipulated plant source population, microbial community, and 12 the abiotic environment, and measured both plant and microbial performance as 13 well as plant traits. Although we found little evidence of interactive effects, we found 14 strong main effects of plant source, microbial treatment, and zinc on both duckweed 15 and microbial growth, with significant variation among both duckweed and microbial 16 communities. Despite strong growth alignment between duckweed and microbes, zinc 17 consistently decreased plant growth, but increased microbial growth. Furthermore, 18 as in recent studies of terrestrial plants, microbial interactions altered a duckweed 19 phenotype (frond aggregation). Our results suggest that the duckweed source pop-20 ulation, its associated microbiome, and the contaminant environment may all need 21 to be considered in real-world phytoremediation efforts. Lastly, we propose that 22 duckweed microbes offer a robust experimental system for study of host-microbiota 23 interactions under a range of environmental stresses.24

Stochastic signaling dynamics expand living cells’ information processing capabilities. An increasing number of studies report that regulators encode information in their pulsatile dynamics. The evolutionary mechanisms that lead to complex signaling dynamics remain uncharacterized, perhaps because key interactions of signaling proteins are encoded in intrinsically disordered regions (IDRs), whose evolution is difficult to analyze. Here we focused on the IDR that controls the stochastic pulsing dynamics of Crz1, a transcription factor in fungi downstream of the widely conserved calcium signaling pathway. We find that Crz1 IDRs from anciently diverged fungi can all respond transiently to calcium stress; however, only Crz1 IDRs from the Saccharomyces clade support pulsatility, encode extra information, and rescue fitness in competition assays, while the Crz1 IDRs from distantly related fungi do none of the three. On the other hand, we find that Crz1 pulsing is conserved in the distantly related fungi, consistent with the evolutionary model of stabilizing selection on the signaling phenotype. Further, we show that a calcineurin docking site in a specific part of the IDRs appears to be sufficient for pulsing and show evidence for a beneficial increase in the relative calcineurin affinity of this docking site. We propose that evolutionary flexibility of functionally divergent IDRs underlies the conservation of stochastic signaling by stabilizing selection.