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A potential multidrug ABC transporter gene from field isolates of Sclerotinia homoeocarpa involved in propiconazole resistance.
H. SANG (1), J. Hulvey (1), J. T. Popko (1), G. Jung (1). (1) University of Massachusetts, Amherst, MA, U.S.A.

An ABC-G transporter gene potentially involved in multi-drug efflux, <i>ShABC1</i>, was identified from RNA-Seq data of <i>Sclerotinia homoeocarpa</i>. Analysis of the <i>ShABC1</i> amino acid sequence indicates that <i>ShABC1</i> is a homolog of <i>PMR1</i>, a multi-drug resistance ABC transporter from <i>Penicillium digitatum</i>. In a previous study, overexpression of an ABC-G transporter gene (<i>ShatrD</i>) in <i>S. homoeocarpa</i> was associated with propiconazole insensitivity. For assessing the involvement <i>ShABC1</i> in propiconazole sensitivity, the relative expression (R.E.) of <i>ShABC1</i> was assayed with quantitative Real-Time PCR before and after treatment of propiconazole (0.1 µg ml<sup>-1</sup>) for 1h in a panel of eight isolates from five sites. Constitutive R.E. of <i>ShABC1</i> in two sets of 8 isolates sampled from two golf courses with previously confirmed practical field resistance were also assayed. Propiconazole insensitive isolates significantly overexpressed <i>ShABC1</i> before and after treatment. The linear relationship between log<sub>10</sub> R.E. of <i>ShABC1</i> and propiconazole EC<sub>50</sub> was highly significant (<i>P</i> < 0.0001). <i>ShABC1</i> and <i>ShatrD</i> expression levels were compared in two insensitive isolates after propiconazole treatment at varying concentrations (0, 0.1, 1, and 5 µg ml<sup>-1</sup>). R.E. of <i>ShABC1</i> was significantly higher than R.E of <i>ShatrD</i> at the 5 µg ml<sup>-1</sup>. R.E. of eight isolates in the panel were assayed 1h after exposure to boscalid at 10 µg ml<sup>-1</sup> to investigate their potential roles in multi-drug resistance. R.E. of <i>ShABC1</i> was significantly induced within insensitive isolates in response to boscalid, however, <i>ShatrD</i> was not. We hypothesize that both genes might play similar roles in propiconazole sensitivity, but may each have unique substrate specificities. <p><p>Keywords: Fungus, Turfgrass, Cool-season

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