A Meloidogyne graminicola Pectate Lyase Is Involved in Virulence and Activation of Host Defense Responses

Jiansong Chen; Zhiwen Li; Borong Lin; Jinling Liao; Kan Zhuo

doi:10.3389/fpls.2021.651627

A Meloidogyne graminicola Pectate Lyase Is Involved in Virulence and Activation of Host Defense Responses

Front Plant Sci. 2021 Mar 22:12:651627. doi: 10.3389/fpls.2021.651627. eCollection 2021.

Authors

Jiansong Chen^{1

2}, Zhiwen Li^{1

2}, Borong Lin^{1

2}, Jinling Liao^{2

3}, Kan Zhuo^{1

2}

Affiliations

¹ Guangdong Laboratory of Lingnan Modern Agriculture, Guangzhou, China.
² Laboratory of Plant Nematology, South China Agricultural University, Guangzhou, China.
³ Guangdong Eco-Engineering Polytechnic, Guangzhou, China.

Abstract

Plant-parasitic nematodes secrete an array of cell-wall-degrading enzymes to overcome the physical barrier formed by the plant cell wall. Here, we describe a novel pectate lyase gene Mg-PEL1 from M. graminicola. Quantitative real-time PCR assay showed that the highest transcriptional expression level of Mg-PEL1 occurred in pre-parasitic second-stage juveniles, and it was still detected during the early parasitic stage. Using in situ hybridization, we showed that Mg-PEL1 was expressed exclusively within the subventral esophageal gland cells of M. graminicola. The yeast signal sequence trap system revealed that it possessed an N-terminal signal peptide with secretion function. Recombinant Mg-PEL1 exhibited hydrolytic activity toward polygalacturonic acid. Rice plants expressing RNA interference vectors targeting Mg-PEL1 showed an increased resistance to M. graminicola. In addition, using an Agrobacterium-mediated transient expression system and plant immune response assays, we demonstrated that the cell wall localization of Mg-PEL1 was required for the activation of plant defense responses, including programmed plant cell death, reactive oxygen species (ROS) accumulation and expression of defense-related genes. Taken together, our results indicated that Mg-PEL1 could enhance the pathogenicity of M. graminicola and induce plant immune responses during nematode invasion into plants or migration in plants. This provides a new insight into the function of pectate lyases in plants-nematodes interaction.

Keywords: Meloidogyne graminicola; RNAi; enzymatic activity; pectate lyase; plant immunity elicitation.