Cloning and Characterization of Pectate Lyases Expressed in the Esophageal Gland of the Pine Wood Nematode Bursaphelenchus xylophilus

Abstract

Two pectate lyase genes (Bx-pel-1 and Bx-pel-2) were cloned from the pine wood nematode, Bursaphelenchus xylophilus. The deduced amino acid sequences of these pectate lyases are most similar to polysaccharide lyase family 3 proteins. Recombinant BxPEL1 showed highest activity on polygalacturonic acid and lower activity on more highly methylated pectin. Recombinant BxPEL1 demonstrated full dependency on Ca2+ for activity and optimal activity at 55 degrees C and pH 8 to 10 like other pectate lyases of polysaccharide lyase family 3. The protein sequences have predicted signal peptides at their N-termini and the genes are expressed solely in the esophageal gland cells of the nematode, indicating that the pectate lyases could be secreted into plant tissues to help feeding and migration in the tree. This study suggests that pectate lyases are widely distributed in plant-parasitic nematodes and play an important role in plant-nematode interactions.

Identification and Characterization of Expansins from Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae)

“…Even though pinewood nematode infected trees usually wither and die within a couple of months (Mamiya, 1975), we still do not understand the molecular and cellular pathophysiology underlying the abilities of pinewood nematodes to infection and propagate in the trees. However, the presence of diverse cell wall degrading enzymes such as endoglucanases (Kikuchi et al, 2004;Smant et al, 1998), pectate lyases (Kikuchi et al, 2006;Popeijus et al, 2000) and expansins (EXPs) (Kikuchi et al, 2009) that to play crucial roles in initiation and progression of the plant diseases are present in B. xylophilus genomes suggested that secreted cell wall degrading enzymes from B. xylophilus may be important factors involved with infections and propagation in host trees.…”

Purification and Characterization of Recombinant Endoglucanases from the Pine Wood NematodeBursaphelenchus xylophilus

“…B. xylophilus endoglucanases appear to have been particularly active at temperatures much higher than those found in the normal environmental conditions that the nematodes encounter. This is also the case for other cell-wall enzymes such as -1,3-glucanase 12) and pectate lyase 13) from B. xylophilus and several invertebrate GHF45 endoglucanases. [14][15][16] Bx-ENGs displayed the highest activity toward lichenan and did not hydrolyze -1,3-1,6 linked glucan (pustran), -1,3 linked glucan (laminarin), galactomannan, xylan, or xyloglucan as substrates.…”

“…13) A mixture of these cell-wall-degrading enzymes might play an important role in softening the cell walls to facilitate the nematode's feeding on plant cells in a tree.…”

The Pathogenesis Related Class 10 proteins in Plant Defense against Biotic and Abiotic Stresses

“…PR-10 proteins have been shown to be transcriptionally responsive across a large range of abiotic stress environments such as drought, salinity, low and high temperatures, heavy metals, wounding and UV exposure [9,72,88]. Several proteins with similarities to the PR-10 family members were identified through two dimensional gel electrophoresis, which were upregulated in peanut callus cultures subjected to salt stress [51].…”

“…Several proteins with similarities to the PR-10 family members were identified through two dimensional gel electrophoresis, which were upregulated in peanut callus cultures subjected to salt stress [51]. Transgenic overexpression of one peanut salinity-induced PR-10 gene (AhSIPR10) in tobacco exhibited enhanced tolerance to salt, heavy metal (ZnCl 2 ) and mannitol-induced drought stress [88]. The expression of CcPR-10 transcripts was induced by wounding and jasmonic acid treatments as well as by armyworm (Spodoptera litura), which suggested that CcPR-10 may be involved in crosstolerance to abiotic and biotic stresses [89].…”