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Plant defensins are recognized for their antifungal properties. However, a few type 1 defensins ( PDF1s) were identified for their cellular zinc (Zn) tolerance properties after a study of the metal extremophile Arabidopsis halleri. In order to investigate whether different paralogues would display specialized functions, the A. halleri PDF1 family was characterized at the functional and genomic levels., Eleven PDF1s were isolated from A. halleri. Their ability to provide Zn tolerance in yeast cells, their activity against Fusarium oxysporum f. sp. melonii, and their level of expression in planta were compared with those of the seven A. thaliana PDF1s. The genomic organization of the PDF1 family was comparatively analysed within the Arabidopsis genus., Ah PDF1s and At PDF1s were able to confer Zn tolerance and Ah PDF1s also displayed antifungal activity. PDF1 transcripts were constitutively more abundant in A. halleri than in A. thaliana. Within the Arabidopsis genus, the PDF1 family is evolutionarily dynamic, in terms of gain and loss of gene copy., Arabidopsis halleri PDF1s display no superior abilities to provide Zn tolerance. A constitutive increase in Ah PDF1 transcript accumulation is proposed to be an evolutionary innovation co-opting the promiscuous PDF1 protein for its contribution to Zn tolerance in A. halleri. [ABSTRACT FROM AUTHOR]

• In an attempt to advance the understanding of ectomycorrhizal symbiosis, which improves mineral nutrition and resistance to abiotic and biotic stresses of most woody plants from temperate and boreal regions, we produced a cDNA library of the ectomycorrhizal fungusHebeloma cylindrosporumin a yeast expression vector. The library was used for functional complementation cloning and for sequencing of 4036 expressed sequence tags (ESTs).• Expression of the library in a yeastade2andtrp1mutant strain allowed cloning of twoHebelomagenes,HcADE2andHcTRP1by functional complementation. This experiment highlighted both the efficiency of the complementation strategy and the quality of the library.• All sequence data available onHebeloma(4596) were analysed and contiged. The whole EST resource is accessibleviaa web interface, which allows searching and navigation through clusters and tentative contigs (TCs).• Analysis of the database revealed a low level of counterparts already identified in other ectomycorrhizal fungi. For example, it allowed identification of a large set of membrane transporters, such as phosphate, potassium, sulphate or micronutrient transporters. Thus, this EST resource provides a valuable tool for research on ectomycorrhiza and symbiotic interactions.New Phytologist(2004)doi: 10.1111/j.1469-8137.2004.01185.x© New Phytologist(2004) [ABSTRACT FROM AUTHOR]