Molecular characterization and functional analysis of two new β‐1,4‐endoglucanase genes (Ha‐eng‐2,Ha‐eng‐3) from the cereal cyst nematode Heterodera avenae

Abstract

Parasitism genes encoding secretory proteins expressed in the pharyngeal glands of plant-parasitic nematodes play a crucial role in nematode parasitism of plants. Two new b-1,4-endoglucanase genes (Ha-eng-2 and Ha-eng-3) expressed in the pharyngeal glands of the sedentary cyst nematode, Heterodera avenae, were cloned. Both of the predicted proteins have a putative signal peptide for secretion and a catalytic domain. Neither peptide linkers nor cellulose binding domains were present. In situ hybridization showed that the transcripts of Ha-eng-2 and Ha-eng-3 accumulated specifically in the two subventral gland cells of H. avenae. RT-PCR analysis confirmed that their transcriptions were strong in the preparasitic and early parasitic second-stage juveniles, and were undetectable at the late parasitic stages of the nematode. Cellulase activities of the recombinant proteins HA-ENG-2 and HA-ENG-3 were confirmed in vitro. Knocking down Ha-eng-2 using RNA interference reduced nematode infectivity by 40%. The results indicate that these b-1,4-endoglucanases can be secreted into plant tissues and play an important role in the wall degradation of plant cells during penetration and the migration of second-stage juveniles in host roots.

Characterisation and functional importance of β-1,4-endoglucanases from the potato rot nematode, Ditylenchus destructor

“…It is hypothesised that a com bination of the mechanical force of stylet thrusts and ne matode cell wall-digesting enzymes promotes the breach of plant cell walls (Davis et al, 2009(Davis et al, , 2011. Support for this hypothesis was recently provided from experiments in which genes for cell-wall-digesting enzymes were si lenced by RNAi-soaking techniques, and host infectivity of the treated nematodes was reduced (Chen et al, 2005;Zhang et al, 2012;Long et al, 2013).…”

“…/Ll,4-endoglucanase expressed exclusively within the subventral glands has been observed in several plantparasitic nematodes (de Boer et al, 1999;Rosso et al, 1999;Gao et al, 2004;Ledger et al, 2006;Haegeman et al, 2008;Long et al, 2013). Secretion of cyst ne matode /3-1,4-endoglucanase was detected during intra cellular migration within host roots (Wang et a l, 1999) but not in developing host-feeding cells (Goellner et al, 2000).…”

“…in various plant-parasitic nematodes (Bera-Maillet et al, 2000;Goellner etal., 2000;Uehara etal., 2001;Gao et al, 2002;Kikuchi et al, 2004;Haegeman et a l, 2008;Peng et al, 2009;Wubben et al, 2010;Fu et al, 2012;Long et al, 2012Long et al, , 2013Hu et al, 2013). These cellulases be long to three CAZyme families.…”

“…Therefore, the cell-wall-degrading and modifying proteins play key roles in the penetration, migration and feeding of this ne matode (Davis et al, 2008). A recent expressed sequence tag (EST) study revealed a series of ESTs with homology to cell-wall-degrading enzymes (Peng et al, 2013).…”

“…Over 70 crops and weeds and a similar number of fungal species have been recorded as hosts (EPPO, 2008). In addition, D. destructor is also considered to be an im portant international quarantine pest (Peng et al, 2013). By comparison with sedentary endoparasites, migratory nematodes such as D. destructor will not induce a feeding structure and always move within the host plants to feed in different plant cells (Moens & Perry, 2009).…”