Abstract

The dominating tree species in southern Swedish forests is Norway spruce (Picea abies), but the knowledge of its defense responses is much more limited than for agricultural species. This study intended to increase the understanding of defense responses towards pathogenic microorganisms in Norway spruce. Three selected Norway spruce genes with a potential role in the defense against pathogenic microorganisms were transformed into Norway spruce and tobacco plants. These genes were: Pa 18, isolated from a cDNA library made from embryogenic cultures, and spi 1 and spi 2, isolated from a cDNA library made from Pythium dimorphum-infected seedling roots. Pa 18 encodes an LTP-like protein. Spi 1 shows similarity to plant defensin genes and spi 2 to cationic peroxidase genes. Overexpression of the genes in embryogenic cultures of Norway spruce, reduced the regeneration capacity. Somatic embryos that expressed Pa 18 ectopically were blocked early in development. Constitutive expression of spi 1 had an inhibitory effect at early developmental stages, and overexpresion of spi 2 increased the stress sensitivity. Furthermore, overexpression of spi 2 resulted in altered lignin histochemistry suggesting that a higher frequency of coniferaldehyde had been incorporated into the lignin polymer.
All three genes inhibited growth of plant pathogenic bacteria: overexpression of Pa 18 in somatic embryos of Norway spruce inhibited growth of Agrobacterium tumefaciens. Tobacco plants expressing spi 1 or spi 2 suppressed growth of Erwinia carotovora. High concentrations of SPI 1 in Norway spruce plants suppressed growth of the pathogenic fungus Heterobasidion annosum, but expression of spi 2 in tobacco plants was ineffective in controlling growth of Phytophthora parasitica var nicotianae.
​​​​​​​This study shows that induced defense responses in Norway spruce can have an important role in the defense against pathogenic microorganisms. Furthermore, it shows that transgenic conifers can be used to test the importance of individual candidate genes in disease resistance.

Keywords

Norway spruce; transformation; defense genes; resistance; lignin; peroxidase; defensin

Published in

Acta Universitatis Agriculturae Sueciae. Silvestria
2001, number: 175
ISBN: 91-576-6059-X
Publisher: Department of Forest Genetics, Swedish University of Agricultural Sciences

SLU Authors

• Elfstrand, Malin

  • Department of Forest Genetics, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Forest Science


Permanent link to this page (URI)

https://res.slu.se/id/publ/107973