Characterization of the Serralysin-like Gene of 'Ca. Liberibacter solanacearum' Associated with Potato Zebra Chip Disease

The non-culturable bacterium ‘Candidatus Liberibacter solanacearum’ (Lso) is the causative agent of zebra chip disease in potato. Computational analysis of the Lso genome revealed a serralysin-like gene based on conserved domains characteristic of genes encoding metalloprotease enzymes similar to serralysin. Serralysin and other serralysin family metalloprotease are typically characterized as virulence factors and are secreted by the type I secretion system (T1SS). The Lso serralysin-like gene is located next to and divergently transcribed from genes encoding a T1SS. Based on its relationship to the T1SS and the role of other serralysin family proteases in circumventing host antimicrobial defenses, it was speculated that a functional Lso serralysin-like protease could be a potent virulence factor. Gene expression analysis showed that from weeks 2 to 6 the expression of the Lso serralysin-like gene was at least “2- fold” higher than week 1, indicating gene expression stays high as the disease progresses. A...