Abstract
Meloidogyne incognita is a root knot nematode (RKN) species which is among the most notoriously unmanageable crop pests with a wide host range. It inhabits plants and induces unique feeding site structures within host roots, known as giant cells (GCs). The cell walls of the GCs undergo the process of both thickening and loosening to allow expansion and finally support nutrient uptake by the nematode. In this study, a comparative in situ analysis of cell wall polysaccharides in the GCs of wild-type Col-0 and the microtubule-defective fra2 katanin mutant, both infected with M. incognita has been carried out. The fra2 mutant had an increased infection rate. Moreover, fra2 roots exhibited a differential pectin and hemicellulose distribution when compared to Col-0 probably mirroring the fra2 root developmental defects. Features of fra2 GC walls include the presence of high-esterified pectic homogalacturonan and pectic arabinan, possibly to compensate for the reduced levels of callose, which was omnipresent in GCs of Col-0. Katanin severing of microtubules seems important in plant defense against M. incognita, with the nematode, however, to be nonchalant about this “katanin deficiency” and eventually induce the necessary GC cell wall modifications to establish a feeding site.
Highlights
Root-knot nematodes (RKN; Meloidogyne spp.) are obligatory parasites that inhabit plant roots, nursing from specially modified host cells to complete their life cycle [1]
The objective of this work was to compare in situ for the first time the cell wall polysaccharides in the giant cells of both wild-type (Col-0) and the fra2 katanin mutant, both infected with M. incognita
We found that callose was present in the giant cells (GCs) cell walls
Summary
Root-knot nematodes (RKN; Meloidogyne spp.) are obligatory parasites that inhabit plant roots, nursing from specially modified host cells to complete their life cycle [1]. M. incognita stage 2 juveniles (J2) enter the host plant close to the root tip; they migrate towards the elongation zone anchor to the root central cylinder, become sedentary and after bypassing host defenses, establish a feeding site [5]. M. incognita juveniles express numerous genes encoding cell wall-degrading enzymes and virulence effectors to enter, migrate into roots, establish feeding site and eventually induce GC formation [6,7]. The feeding site consists of several GCs enclosed in a macroscopically visible gall, a typical characteristic of RKN infestation. The male leaves the root and does not harm host plants [9]
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