Broad-spectrum disease resistance to necrotrophic and biotrophic pathogens in transgenic carrots (Daucus carota L.) expressing an Arabidopsis NPR1 gene

摘要

The development of transgenic plants highly resistant to a range of pathogens using traditional signal gene expression strategies has been largely ineVective. ModiWcation of systemic acquired resistance (SAR) through the overexpression of a controlling gene such as NPR1 (non-expressor of PR genes) oVers an attractive alternative for augmenting the plants innate defense system. The Arabidopsis (At) NPR1 gene was successfully introduced into ‘Nantes Coreless’ carrot under control of a CaMV 35S promoter and two independent transgenic lines (NPR1-I and NPR1-XI) were identiWed by Southern and Northern blot hybridization. Both lines were phenotypically normal compared with non-transformed carrots. Northern analysis did not indicate constitutive or spontaneous induction in carrot cultures of SAR-related genes (DcPR-1, 2, 4, 5 or DcPAL). The duration and intensity of expression of DcPR-1, 2 and 5 genes were greatly increased compared with controls when the lines were treated with puriWed cell wall fragments of Sclerotinia sclerotiorum as well as with 2,6-dichloroisonicotinic acid. The two lines were challenged with the necrotrophic pathogens Botrytis cinerea, Alternaria radicina and S. sclerotiorum on the foliage and A. radicina on the taproots. Both lines exhibited 35–50% reduction in disease symptoms on the foliage and roots when compared with non-transgenic controls. Leaves challenged with the biotrophic pathogen Erysiphe heraclei or the bacterial pathogen Xanthomonas hortorum exhibited 90 and 80% reduction in disease development on the transgenic lines, respectively. The overexpression of the SAR controlling master switch in carrot tissues oVers the ability to control a wide range of diVerent pathogens, for which there is currently little genetic resistance available.