Characterization of Cell-Death-Inducing Members of the Pectate Lyase Gene Family in Phytophthora capsici and Their Contributions to Infection of Pepper

Abstract

Pectate lyases (PL) play a critical role in pectin degradation. PL have been extensively studied in major bacterial and fungal pathogens of a wide range of plant species. However, the contribution of PL to infection by oomycete pathogens remains largely unknown. Here, we cloned 22 full-length pectate lyase (PcPL) genes from a highly aggressive strain of Phytophthora capsici SD33. Of these, PVX agroinfiltration revealed that 12 PcPL genes were found to be highly induced during infection of pepper by SD33 but the induction level was twofold less in a mildly aggressive strain, YN07. The four genes with the highest transcript levels as measured by by quantitative reverse-transcription polymerase chain reaction (PcPL1, PcPL15, PcPL16, and PcPL20) also produced a severe cell death response following transient expression in pepper leaves but the other eight PcPL genes did not. Overexpression of these four genes increased the virulence of SD33 on pepper slightly, and increased it more substantially during infection of tobacco. Overexpression of the genes in YN07 restored its aggressiveness to near that of SD33. Gene silencing experiments with the 12 PcPL genes produced diverse patterns of silencing of PcPL genes, from which it could be inferred from regression analysis that PcPL1, PcPL16, and PcPL20 could account for nearly all of the contributions of the PcPL genes to virulence.

Genomics analysis of Aphanomyces spp. identifies a new class of oomycete effector associated with host adaptation

“…Secreted PL1 are detected in group II or III, where gene expression is less abundant in mycelium as compared to zoospore and infection stages. This pattern is similar to the one observed in Phytophthora capsici, where the PL1 family in combination with PL16 and PL20 (absent in the Ae genome) account for nearly all of the contribution of the 22 PL genes to Phytophthora virulence [ 59 ]. Most of the carbohydrate esterases (CE) showed a consistent low to medium expression in the different life stages (Additional file 5 : Figure S3A, Additional file 3 : ST2i).…”

Molecular Characterization of A Novel Effector Expansin-like Protein from Heterodera avenae that Induces Cell Death in Nicotiana benthamiana

“…The secreted proteins from plant pathogens have been tested directly for the induction or suppression of plant defence responses through its expression in plant leaves, as an alternative to obtain stable transgenic plants. In this way, virulence or avirulence effectors that can induce cell death in plants have been identified from several eukaryotic plant pathogens42434445. An expansin protein from G. rostochiensis , GrEXPB2, which lacks a carbohydrate-binding domain (CBD) found in expansins and expansin-like proteins, also induced chlorosis in N. benthamiana and cell death in tomato and potato plant46.…”

The L-type Ca2+ Channel Blocker Nifedipine Inhibits Mycelial Growth, Sporulation, and Virulence of Phytophthora capsici

“…Recent studies of the biological function of fungal laccases suggest that this enzyme plays an important role in fungal morphogenesis and fungal virulence ( Li et al, 2013 ). In P. capsici , pectate lyase and laccase activities are important for successful infection during plant–pathogen interactions ( Feng and Li, 2014 ; Fu et al, 2015 ). Laccases, which served as blue copper oxidases, catalyze the one-electron oxidation (e.g., aromatic amines and phenolics) and other electron-rich substrates; there also has a reduction of O 2 to H 2 O concomitantly.…”