Identification and Functional Analysis of NLP-Encoding Genes from the Postharvest Pathogen Penicillium expansum

Abstract

<i>Penicillium expansum</i> is a major postharvest pathogen that infects different fruits, mainly through injuries inflicted during harvest or subsequent handling after harvest. Several effectors were suggested to mediate pathogenicity of <i>P. expansum</i> in fruit tissue. Among these effectors Nep1-like proteins (NLPs), produced by various microorganisms with different lifestyles, are known for their ability to induce necrosis in dicot plants and were shown to be involved in virulence of several plant-related pathogens. This study was aimed at the identification and functional characterization of two NLP genes found in the genome of <i>P. expansum</i>. The genes were designated <i>Penlp1</i> and <i>Penlp2</i> and were found to code type1 and type3 NLP respectively. Necrosis-inducing activity of the two proteins was demonstrated by transient expression in <i>Nicotiana benthamiana</i> leaves. While <i>Penlp1</i> expression was induced during apple infection and in liquid culture, the highest level of <i>Penlp2</i> expression was found in ungerminated spores. Deletion of <i>Penlp1</i>, but not <i>Penlp2</i>, resulted in reduced virulence on apples manifested by reduced rate of lesion development (disease severity).