Cloning, sequence and characterization of a sunflower (Helianthus annuus L.) pathogen-induced gene showing sequence homology with auxin-induced genesfrom plants

The establishment of a plant-pathogen interaction involves changes in gene expressions in both organisms. To isolate Helianthus annuus genes whose exp ression is induced during processes of resistance to Plasmopara halstedii, a comparison of the expression pattern of healthy sunflowers was made with sunflowers infected with 2 races of P. halstedii, either virulent or avirul ent, using differential display of mRNA. A full-length cDNA, HaAC1, represe nting a sunflower gene whose expression is enhanced during early stages of the incompatible interaction, was isolated. Different timing of RNA accumul ation is observed between compatible and incompatible combinations. Sequenc e analysis and database search revealed significant homology with auxin-ind uced genes from plants. The expression of this gene, is also induced after treatment with 2,-dichlorophenoxyacetic acid (2,4-D), salicylic acid (SA) a nd wounding.