Cell Wall Alterations in Nematode-Infected Roots

Abstract

Abstract Sedentary plant-parasitic nematodes induce sophisticated feeding sites in roots of many crop plants causing tremendous yield losses in agriculture worldwide. The most damaging genera are cyst and root-knot nematodes forming syncytia and giant cells embedded in root galls, respectively. In addition to many morphological changes, elaborated cell wall alterations play an important role during the formation of both feeding sites and thus are essential for survival and reproduction of these parasites. Plant-parasitic nematodes were the first animals shown to produce cell wall modifying and degrading proteins and enzymes. Already during the migration through the root tissue, infective juveniles secrete e.g. cellulases and expansins, which, in addition to mechanical cell wall disruption performed with the stylet, considerably facilitate the infection process. At the begining of sedentary stage secretions from the dorsal gland trigger the formation of a feeding site in the central cylinder. These widely unknown substances change the host gene expression affecting, in addition to many others, also cell wall-related processes leading to various architectural modifications in host cells. Several cellulolytic and pectolytic enzymes as well as expansins are specifically expressed and play an important function during the formation of the feeding sites and development of the nematodes. This chapter summarizes data on cell wall modifications in plant tissues infected with cyst and root-knot nematodes as well as on involvement of different proteins, of both nematode and plant origin, during migration and sedentary phase of nematode parasitism.