Abstract
Plant parasitic nematodes must be able to locate and feed from their host in order to survive. Here we show that Pratylenchus coffeae regulates the expression of selected cell-wall degrading enzyme genes relative to the abundance of substrate in root exudates, thereby tailoring gene expression for root entry of the immediate host. The concentration of cellulose or xylan within the exudate determined the level of β-1,4-endoglucanase (Pc-eng-1) and β-1,4-endoxylanase (Pc-xyl) upregulation respectively. Treatment of P. coffeae with cellulose or xylan or with root exudates deficient in cellulose or xylan conferred a specific gene expression response of Pc-eng-1 or Pc-xyl respectively with no effect on expression of another cell wall degrading enzyme gene, a pectate lyase (Pc-pel). RNA interference confirmed the importance of regulating these genes as lowered transcript levels reduced root penetration by the nematode. Gene expression in this plant parasitic nematode is therefore influenced, in a host-specific manner, by cell wall components that are either secreted by the plant or released by degradation of root tissue. Transcriptional plasticity may have evolved as an adaptation for host recognition and increased root invasion by this polyphagous species.
Highlights
Plant pathogens must recognise and respond to host signals in order to survive, with root exudates important for those that are soil-borne [1,2,3]
Plant parasitic nematodes feed from plant roots to support their development
The relative expression of each gene correlates with the abundance of the encoded enzyme substrate in the nematode environment, indicating that the nematode perceives these components and responds by tailoring gene expression for what is currently required for host-parasitism
Summary
Plant pathogens must recognise and respond to host signals in order to survive, with root exudates important for those that are soil-borne [1,2,3]. Plant parasitic nematodes are amongst the four most economically important groups of plant pathogens, causing >$80 billion of damage to crops globally each year [6] They are principally root parasites and root exudates play an important role in host-nematode interactions, inducing nematode hatching and thrusting of an anterior, hollow stylet used to penetrate plant cell walls and during feeding [7, 8, 9]. Nematodes orientate to plant roots in response to chemical gradients (e.g. monosaccharides, carbon dioxide, volatile organic compounds and amino acids) provided by root exudates [7]. Plant hormones such as ethylene and auxin, and their signalling pathways, have been implicated in the attractiveness of roots towards nematodes [10, 11, 12]
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