ZmGLP1, a Germin-like Protein from Maize, Plays an Important Role in the Regulation of Pathogen Resistance

Abstract

A gene encoding a protein similar to germin-like proteins (GLPs) was obtained from maize (<i>Zea mays</i>) and designated as <i>ZmGLP1</i>. Based on the <i>ZmGLP1</i> conserved domain and phylogenetic status, <i>ZmGLP1</i> was grouped into GLP subfamily b and has high similarity to <i>OsGLP8-14</i> from <i>Oryza sativa</i>. <i>ZmGLP1</i> is expressed in different maize tissues during different growth stages and is mainly expressed in the stems and leaves. The induced expression patterns confirmed that <i>ZmGLP1</i> is differentially expressed under abiotic and hormone stress; it had an early response to jasmonic acid (JA) and ethephon (ET) but a late response to salicylic acid (SA) and was significantly upregulated under <i>Bipolaris maydis</i> infection. The overexpression of <i>ZmGLP1</i> in <i>Arabidopsis</i> improved the resistance to biotrophic <i>Pseudomonas syringae</i> pv. tomato DC3000 (<i>Pst</i>DC3000) and necrotrophic <i>Sclerotinia sclerotiorum</i> by inducing the expression of JA signaling-related genes. Moreover, the hydrogen peroxide (H₂O₂) content increased due to the overexpression of <i>ZmGLP1</i> in <i>Arabidopsis</i> after pathogen infection. Compared to the wild-type control, the H₂O₂ content of <i>ZmGLP1</i>-overexpressing <i>Arabidopsis</i> infected by <i>PstDC3000</i> increased significantly but was lower in transgenic plants infected with <i>S. sclerotiorum</i>. Furthermore, high-performance liquid chromatography-tandem mass (HPLC-MS/MS) spectrometry showed that the JA contents of <i>ZmGLP1</i>-overexpressing <i>Arabidopsis</i> markedly increased after pathogen infection. However, the improved resistance of <i>ZmGLP1</i>-overexpressing <i>Arabidopsis</i> pretreated with the JA biosynthetic inhibitor, sodium diethyldithiocarbamate trihydrate (DIECA), was suppressed. Based on these findings, we speculate that <i>ZmGLP1</i> plays an important role in the regulation of <i>Arabidopsis</i> resistance to biotrophic <i>Pst</i>DC3000 and necrotrophic <i>S. sclerotiorum</i>; the regulatory effects are achieved by inducing plant oxidative burst activity and activation of the JA signaling pathway.