Molecular Insights in the Susceptible Plant Response to Nematode Infection

Abstract

Sedentary endoparasitic nematodes have evolved sophisticated strategies to form permanent feeding sites within host plant roots to ensure their survival. The process of feeding site formation entails an elaborate transformation of normal root cells into enlarged, multinucleate, and metabolically active cell types to supply the nutritional needs of the nematode. The signal-exchange that occurs between nematodes and their hosts to trigger the chain of molecular events associated with feeding cell formation has not been resolved. Presumably, the signals for the induction of feeding cells come from the nematode; thus, secretions originating in the esophageal gland cells and directly injected through the stylet into host tissues during parasitism have been implicated as key molecules. It is evident from the distinct morphological features of feeding sites that the nematode signals likely interfere with fundamental aspects of plant cell biology and differentiation. Molecular studies have shown that these changes are accompanied by extensive alterations in plant gene expression. Researchers have taken advantage of a wide array of methodologies to catalogue the genes as either up-or down-regulated in nematode feeding sites, and technological advances are now enabling feeding cell-specific analyses. As comprehensive profiles of genes expressed in feeding sites are generated, it has become increasingly important to determine which genes play essential roles in their formation. In the future, the true challenge will be to integrate our knowledge of nematode signals with host cell responses to elucidate a complete picture of feeding site formation.

Gene expression analysis inMusa acuminataduring compatible interactions withMeloidogyne incognita

“…Similarly, plant genes encoding hydrolases such as endoglucanases, pectinases and expansins are also commonly upregulated following nematode infection, facilitating the establishment of feeding sites (Gheysen and Mitchum, 2009). Within our data sets, MapMan pathway analysis generally indicated an upregulation of genes associated with the cell wall at early time points of the interaction in both genotypes, diminishing over time.…”

Manipulation of Auxin Transport in Plant Roots during Rhizobium Symbiosis and Nematode Parasitism

“…The impressive transformation of the plant cell infected by sedentary endoparasitic nematodes goes along with a plethora of physiological and molecular changes (Jammes et al, 2005;Ithal et al, 2007;Gheysen and Mitchum, 2009). Similar to nodule initiation, an enhanced auxin response has been visualized at the infection sites of both cyst and root-knot nematodes, whereas auxin signaling mutants have shown significantly lower nematode infection (Hutangura et al, 1999;Goverse et al, 2000;Karczmarek et al, 2004;Grunewald et al, 2008).…”

“…In a similar manner, giant cells must push away several layers of host tissue to grow radially, and syncytia must reprogram neighboring cells to integrate them. Indeed, endoglucanases, expansins, and several other host cell wall modifying enzymes are active in the NFS overlying cells (Goellner et al, 2001;Vercauteren et al, 2002;Wieczorek et al, 2008;Gheysen and Mitchum, 2009). This not only suggests that LAX3 could be involved in the auxin accumulation in neighboring cells but also that the auxin-dependent activation mechanisms of cell wall-modifying enzymes could be identical in NFS and in lateral root outgrowth.…”

The Jasmonate Pathway Is a Key Player in Systemically Induced Defense against Root Knot Nematodes in Rice

“…RKN transform the punctured cells into so-called giant cells, which are kept alive as their food resource throughout their life cycle. During this infection process, nematodes induce changes in the plant's gene expression patterns in both locally infected and systemic tissues (Gheysen and Mitchum, 2009). The role of plant defense pathways in nematode infection has only been investigated for dicotyledons, but even there merely fragmentary and often contradictory data are available.…”