Isolation, expression and comparison of a pectate lyase produced by <i>Fusarium oxysporum<I> f.sp. <i>cubense<i> race 1 and race 4

Abstract

Fusarium wilt is a devastating disease in banana production. For example, cultivar Gros Michel was destroyed by Fusarium oxysporum f.sp. cubense race 1 (FOC1) of the pathogen. Cultivar Cavendish is
resistant to FOC1, but a newly occurring race 4 (FOC4) was found to be able to infect Cavendish. Studying the fungal pathogenicity is an important step towards the disease control. In this study, we cloned two pl1 genes (723 bp and 240 aa), encoding pectate lyase 1 (PL1) from both FOC1 and FOC4, into the expression vector pPICZaA and the two genes were expressed in Pichia pastoris strains of SMD1168. The recombinant PL1, r-FOC1-PL1 and r-FOC4-PL1, were purified as active extracellular proteins. The optimal PL activity was observed at 50°C and pH 10. Both recombinant PL1 retained >72% activity at pH 3.0 to 11.0 and >70% activity at 10 to 70°C. Activity of the recombinant PL1 required
calcium ions with the optimum activity at 0.75 mM CaCl₂. This is the first isolation and purification of PL1 from pathogenic FOC.

Keywords: Pectate lyase, Fusarium oxysporum f.sp. cubense, Fusarium wilt, banana