Effects of sugar beet chitinase IV on root-associated fungal community of transgenic silver birch in a field trial

Abstract

Heterogenous chitinases have been introduced in many plant species with the aim to increase the resistance of plants to fungal diseases. We studied the effects of the heterologous expression of sugar beet chitinase IV on the intensity of ectomycorrhizal (ECM) colonization and the structure of fungal communities in the field trial of 15 transgenic and 8 wild-type silver birch (Betula pendula Roth) genotypes. Fungal sequences were separated in denaturing gradient gel electrophoresis and identified by sequencing the ITS1 region to reveal the operational taxonomic units. ECM colonization was less intense in 7 out of 15 transgenic lines than in the corresponding non-transgenic control plants, but the slight decrease in overall ECM colonization in transgenic lines could not be related to sugar beet chitinase IV expression or total endochitinase activity. One transgenic line showing fairly weak sugar beet chitinase IV expression without significantly increased total endochitinase activity differed significantly from the non-transgenic controls in the structure of fungal community. Five sequences belonging to three different fungal genera (Hebeloma, Inocybe, Laccaria) were indicative of wild-type genotypes, and one sequence (Lactarius) indicated one transgenic line. In cluster analysis, the non-transgenic control grouped together with the transgenic lines indicating that genotype was a more important factor determining the structure of fungal communities than the transgenic status of the plants. With the tested birch lines, no clear evidence for the effect of the heterologous expression of sugar beet chitinase IV on ECM colonization or the structure of fungal community was found.

Impact of endochitinase-transformed white spruce on soil fungal communities under greenhouse conditions

“…Nevertheless, these chitinase-expressing silver birches were shown to be more resistant to the leaf spot disease of birch caused by Pyrenopeziza betulicola (Pappinen et al, 2002). Pasonen et al (2009) showed that the mycorrhizal colonization rate of a transformed line of silver birch overexpressing chitinase 3.7 times compared with the control was similar to that of untransformed trees and other wildtype clones. Pasonen et al (2009) showed that the mycorrhizal colonization rate of a transformed line of silver birch overexpressing chitinase 3.7 times compared with the control was similar to that of untransformed trees and other wildtype clones.…”

Biotechnological efforts for preserving and enhancing temperate hardwood tree biodiversity, health, and productivity

“…Studies with silver birch looked at overexpression of 4-coumarate:coenzyme A ligase, a lignin biosynthesis gene involved in interactions between roots and soil microorganisms (Seppänen et al 2007). Overexpression of sugar beet chitinase IV in silver birch decreased plant material palpability to insect foragers while increasing resistance to fungal disease (Vihervuori et al 2008;Pasonen et al 2009). American chestnut has been transformed to express the wheat germin-like oxalate oxidase gene in an effort to bolster its resistance to fungal pathogens (Welch et al 2007).…”

Comparison of variation in adaptive traits between wild-type and transgenic silver birch (Betula pendula) in a field trial

“…The transgenic lines (GM 11 and GM7 not included) were classified into three groups by messenger ribonucleic acid (mRNA) accumulation, high expression (GM4, GM8, GM10, GM12, GM14 and GM15), intermediate expression (GM2, GM3, GM5 and GM9) and low expression (GM1, GM6 and GM13) (Pasonen et al 2004). The total endochitinase activity of selected GM lines (GM2, GM3,GM4, GM8, GM10, GM14 and GM15) and one control line (Ca) was measured by fluorimetric assay for endochitinase from the roots and was shown to be higher (from 1.1-to 3.7-fold) than in the control (Pasonen et al 2009). The number of inserts in the transgenic lines, confirmed by Southern analysis, was estimated to vary from two to four (Pappinen et al 2002).…”

“…The in vitro cultures of the seven non-transgenic (wild-type) silver birch clones were initiated from bud meristems and micropropagated by axillary shoot multiplication method in similar growing conditions as the transgenic lines and the two controls. For more detailed description of the clone JR 1/4 and the wild-type clones, see Pasonen et al (2009).…”

“…We have previously reported the effects of sugar beet chitinase IV (chiIV) gene on disease resistance (Pasonen et al 2004), growth and leaf phenology and root-associated fungal community (Pasonen et al 2009) of transgenic silver birch lines. The resistance characteristics of chitinase transgenic lines were studied against two fungal leaf diseases, birch rust (Melampsorium betulinum) and birch leaf spot (Pyrenopeziza betulicola), in a field trial.…”