Chitinase, chitosanase and β-1,3-glucanase activities in Allium and Pisum roots colonized by Glomus species

Abstract

By using a two-dimensional polyacrylamide gel electrophoresis (PAGE) system, one major additional band with chitinase activity could be detected in Allium porrum (leek) root extracts after colonization by Glomus versiforme or Glomus intraradix when compared to control root extracts. After separation under native conditions in the first dimension, this band was observed both in the Davis system (designed to separate native acidic or neutral proteins) and in the Reisfeld system (designed to separate basic proteins). After the second dimension in sodium dodecyl sulfate (SDS)-PAGE under non-reducing conditions, its apparent molecular mass was determined to be about 30 kDa. In Glomus fasciculatum-colonized root extracts of Allium cepa (onion), four additional bands with chitinase activity were found. The same additional bands were obtained in onion roots colonized by the other Glomus species. Among the four bands, one of them was separated in the first dimension in both the Davis system and the Reisfeld system, two were only detected as acidic or neutral isoforms, while the last one was present as a basic isoform. Their apparent molecular masses were estimated at 33, 35 and 50 kDa. In vesicular-arbuscular mycorrhizae (VAM)-colonized pea root extracts, one acidic chitinase isoform was strongly stimulated while another acidic isoform was less highly induced in the various mycorrhizal interactions. Their apparent molecular masses were 30 and 47 kDA. Chitosanase activities were detected in leek and onion roots colonized by the different VAM fungi, while no chitosanase was observed in either non-mycorrhizal or VAM-colonized pea roots extracts. In VAM-colonized leek roots, the main chitosanase activity had an estimated apparent molecular mass of 20 kDa as determined by SDA-PAGE under non-reducing conditions. Endomycorrhizal onion roots exhibited three chitosanases with estimated apparent molecular masses of 14, 20 and 35 kDa, the two latter being induced by VAM fungal colonization. Finally, no induction of β-1,3-glucanase activity was detected in VAM-colonized roots of leek and onion. In pea roots, one β-1,3-glucanase activity was revealed, but it was not present in all VAM interactions.