Host-specific signatures of the cell wall changes induced by the plant parasitic nematode, Meloidogyne incognita

Refik Bozbuga,Peter E. Urwin,Catherine J. Lilley,J. Paul Knox

doi:10.1038/s41598-018-35529-7

Abstract

Root-knot nematodes (Meloidogyne spp.) are an important group of plant parasitic nematodes that induce within host plant roots unique feeding site structures, termed giant cells, which supply nutrient flow to the nematode. A comparative in situ analysis of cell wall polysaccharides in the giant cells of three host species (Arabidopsis, maize and aduki bean) infected with Meloidogyne incognita has been carried out. Features common to giant cell walls of all three species include the presence of high-esterified pectic homogalacturonan, xyloglucan and pectic arabinan. The species-specific presence of xylan and mixed-linkage glucan (MLG) epitopes in giant cell walls of maize reflected that host’s taxonomic group. The LM5 galactan and LM21 mannan epitopes were not detected in the giant cell walls of aduki bean but were detected in Arabidopsis and maize giant cell walls. The LM2 arabinogalactan-protein epitope was notable for its apparent global variations in root cell walls as a response to infection across the three host species. Additionally, a set of Arabidopsis cell wall mutants were used to determine any impacts of altered cell wall structures on M. incognita infection. Disruption of the arabinogalactan-protein 8 gene had the greatest impact and resulted in an increased infection rate.

Highlights

Plant parasitic nematodes are obligate parasites that infect mainly root tissue of a wide range of plant species
Enhanced levels of heteroxylan with the commelinid monocotyledon feature of feruloylation would be expected, and the presence of mixed-linkage glucan (MLG) characteristic of the Poaceae. These differences were reflected in the epitopes detected in the cell walls of Arabidopsis, aduki bean and maize all infected with the same root-knot nematode species, M. incognita
Our results show that detectable galactan is suppressed in the walls of giant cells induced in aduki bean; perhaps suggesting an additional factor to increase cell wall flexibility, highlighted above, as a possible important attribute of giant cell walls

Summary

Introduction

Plant parasitic nematodes are obligate parasites that infect mainly root tissue of a wide range of plant species. A large proportion of nematode damage to crops worldwide is inflicted by two major groups of sedentary endoparasites, the cyst nematodes (Heterodera spp. and Globodera spp.) and root-knot nematodes (Meloidogyne spp; RKN) that induce specialised feeding structures termed syncytia and giant cells respectively[1,2]. These two types of feeding site share some structural features and a common function as a sink tissue for delivering nutrients to the nematode, they are formed by distinct processes[3]. In addition a series of Arabidopsis mutations influencing cell wall structures were studied in relation to their impact on RKN infection

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