Novel point mutations in β-tubulin gene for carbendazim resistance maintaining nematode pathogenicity of Paecilomyces lilacinus

Abstract

The application of fungicides is so critical, especially in greenhouses, to avoid fungal infections. Carbendazim, an inhibitor of tubulin biosynthesis, is the most widely known broad-spectrum benzimidazole fungicide. The application of carbendazim affects other beneficial fungi as well. Paecilomyces lilacinus 36-1 (Pl36-1) is a beneficial fungus used for biological control, and the most effective biocontrol agents of nematode eggs. The Pl36-1 is sensitive to carbendazim (0.3 μg/ml). There is a general consensus that the mechanisms of resistance to carbendazim in the β-tubulin gene have been analyzed in detail. However, no studies were conducted on P. lilacinus strains. In the present study, two carbendazim-resistant mutants of Pl36-1, P50 and P100, were obtained from UV exposure and tested. The β-tubulin gene fragments were cloned and sequenced in the three strains, Pl36-1, P50 and P100. The resistance to carbendazim was developed when amino acid substitutions occurred at β-tubulin gene positions of S145A, T185A and F200Y. The β-tubulin gene was overexpressed in Pl36-1 strains. The β-tubulin expression level of the overexpressed mutant (PL3), quantified by qRT-PCR, was increased 4-folds over its normal level in Pl36-1. In vitro, the PL3 was resistant to carbendazim with maintaining growth, sporulation and pathogenicity rates. Three-year field trial demonstrated that P100 and PL3 strains exhibited carbendazim resistance combined with high nematode reduction and yield improvement.

Teladorsagia circumcincta beta tubulin: the presence of the E198L polymorphism on its own is associated with benzimidazole resistance

“…According to Avramenko et al [23], the codon GTA (V) could be an intermediate step between GAA (E) and TTA (L), or CTA (L) in our case. Taking into account that E198V (GAA > GTA) polymorphism has also been associated with BZ resistance in fungi [28], Avramenko et al [23] hypothesized that the presence of V could confer an intermediate level of resistance, lower than that of E198L. It is important to mention that the amino acid valine is coded by GTA, with T at the second position of the codon, in the same way as leucine (CTA or TTA).…”

The role of a phospholipase (PLD) in virulence of Purpureocillium lilacinum (Paecilomyces lilacinum)

“…Strains and culture conditions P. lilacinum 36-1 was isolated from eggs of Meloidogyne incognita in Hubei Province. The weak pathogenic P. lilacinum mutant strain, pt386 was obtained using ATMT method in our previous work [23]. These strains were incubated on potato dextrose agar (PDA) medium at 28 C. A. tumefaciens AGL-1 was mediated in P. lilacinum 36-1 strain, and cultured on LuriaeBertani (LB) [24] plates containing 50 mg/ml of rifampicin and 100 mg/ml of streptomycin at 25 C.…”

Teladorsagia Circumcincta Beta Tubulin: The Presence of the E198L Polymorphism on Its Own is Associated with Benzimidazole Resistance

“…According to Avramenko et al [23], the codon GTA (V) could be an intermediate step between GAA (E) and TTA (L), or CTA (L) in our case. Taking into account that E198V (GAA > GTA) polymorphism has also been associated with BZ resistance in fungi [27], Avramenko et al [23] hypothesized that the presence of V could confer an intermediate level of resistance, lower than that of E198L. It is important to mention that the amino acid valine is coded by GTA, with T at the second position of the codon, in the same way as leucine (CTA or TTA).…”