Olpidium radicale Schwartz & Cook fide Lange & Insunza does not encompass O. radicale Schwartz & Cook emended Cook 1935. Thus, the combination Olpidium bornovanus (Sahtiyanci) Karling is accepted. Single sporangial isolates of O. bornovanus and Olipidium brassicae were prepared from bulk cultures trapped on cucurbit hosts using soils or roots obtained from France, California, Canada, and Brazil. The O. bornovanus isolates comprised three host-specific strains (cucumber, melon, and squash) based on the host in which they multiplied abundantly. All strains reproduced moderately well in watermelon, slightly in mung bean, and not at all in lettuce, cauliflower, red clover, or timothy. Two of three O. brassicae isolates trapped on melon had host specificity similar to that of the melon strains of O. bornovanus and the third was plurivorous. The vegetative generation time of O. bornovanus was longer (5+ days) than that of O. brassicae (3+ days). The O. bornovanus isolates grew at temperatures of 18–30 °C, whereas O. brassicae isolates did not grow at 30 °C. Key words: Olpidium bornovanus, Olpidium radicale, Olpidium brassicae, cucurbit hosts, host specificity.

Zoospores of 12 isolates O. bornovanus from geographically diverse sites and representing the three host specific cucurbit strains were tested as vectors for seven viruses using watermelon bait plants and the in vitro acquisition method. All isolates of the cucumber, melon, and squash strains transmitted melon necrotic spot carmovirus (MNSV) and cucumber necrosis tombusvirus (CNV) but none transmitted petunia asteroid mosaic tombusvirus (PAMV) or tobacco necrosis necrovirus (TNV). The isolates varied as vectors of three other carmoviruses: cucumber leaf spot virus (CLSV); cucumber soil borne virus (CSBV); and squash necrosis virus (SqNV). All cucumber isolates transmitted CLSV and SqNV but not CSBV. Some of the melon isolates transmitted CLSV and SqNV but none transmitted CSBV. Two squash isolates transmitted CSBV and SqNV but not CLSV. Two isolates of O. brassicae transmitted only TNV and a third did not transmit any of the viruses. The species of bait plant sometimes affected transmission. The most efficient vector strains of O. bornovanus, as determined by reducing zoospores and virus in the inoculum, were the cucumber strain for CLSV; the cucumber strain for CNV if cucumber was the bait plant or melon strain if watermelon was the bait plant; and the squash strain for SqNV. The plurivorous strain of O. brassicae was the most efficient vector of TNV. Olpidium bornovanus is the first vector reported for CSBV and is confirmed as a vector of SqNV. It is proposed that all carmoviruses may have fungal vectors. Ligniera sp. did not transmit any of the viruses in one attempt.Abbreviations: CLSV --cucumber leaf spot virus; CNV --cucumber necrosis virus; CSBV = cucumber soil borne virus; MNSV = melon necrotic spot virus; PAMV --petunia asteroid mosaic virus; SqNV = squash necrosis virus; TNV = tobacco necrosis virus; TBSV --tomato bushy stunt virus.

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Summary The morphological transition of the opportunistic fungal pathogen Candida albicans from budding to hyphal growth has been implicated in its ability to cause disease in animal models. Absence of SR-like RNA-binding protein Slr1 slows hyphal formation and decreases virulence in a systemic candidiasis model, suggesting a role for post-transcriptional regulation in these processes. SR (serine-arginine)-rich proteins influence multiple steps in mRNA metabolism and their localization and function are frequently controlled by modification. We now demonstrate that Slr1 binds to polyadenylated RNA and that its intracellular localization is modulated by phosphorylation and methylation. Wildtype Slr1-GFP is predominantly nuclear, but also co-fractionates with translating ribosomes. The non-phosphorylatable slr1-6SA-GFP protein, in which six serines in SR/RS clusters are substituted with alanines, primarily localizes to the cytoplasm in budding cells. Intriguingly, hyphal cells display an slr1-6SA-GFP focus at the tip near the Spitzenkörper, a vesicular structure involved in molecular trafficking to the tip. The presence of slr1-6SA-GFP hyphal tip foci is reduced in the absence of the mRNA-transport protein She3, suggesting that unphosphorylated Slr1 associates with mRNA-protein complexes transported to the tip. The impact of SLR1 deletion on hyphal formation and function thus may be partially due to a role in hyphal mRNA transport.