Transgenic Betula pendula expressing sugar beet chitinase IV forms normal ectomycorrhizae with Paxillus involutus in vitro

Abstract

Mycorrhizal fungi contain chitin in their cell walls and may be influenced by transgenic chitinases. This study examined the ability of a transgenic tree, silver birch (Betula pendula Roth), constitutively expressing the sugar beet chitinase IV gene, to form ectomycorrhizae with Paxillus involutus (Batsch) Fr. Eight transgenic lines showing varying levels of sugar beet chitinase IV expression and the non-transgenic control plants were inoculated by P. involutus in vitro, and the morphology of the mycorrhizae, mycorrhization efficiency and shoot and root fresh weights were studied. All the transgenic birch lines were able to form normal ectomycorrhizae containing distinctive mantles and Hartig nets. The level of sugar beet chitinase IV expression had no significant influence on mycorrhizal colonization. The only significant differences between transgenic and control plants were detected in weight parameters. According to these results, the expression of sugar beet chitinase IV in silver birch is not deleterious to formation of ectomycorrhizae between birch and P. involutus.

Keywords:

• Mycorrhizal colonization
• risk assessment
• silver birch
• transgenic tree

The authors wish to thank Dr J. Mikkelsen (Danisco, Denmark) for providing the plasmid pBKL4K4 containing the chitinase IV gene from sugar beet, Jouko Närhi for technical assistance during the cultivation of seedlings, and MSc Albor Dobón Alonso for assistance in molecular analyses. This study was funded by the Academy of Finland (76 710, 80638, 45690 and agr. no. 810).