Understanding the functional connections between genes, proteins, metabolites and mineral ions is one of biology's greatest challenges in the postgenomic era. We describe here the use of mineral nutrient and trace element profiling as a tool to determine the biological significance of connections between a plant's genome and its elemental profile. Using inductively coupled plasma spectroscopy, we quantified 18 elements, including essential macro- and micronutrients and various nonessential elements, in shoots of 6,000 mutagenized M2 Arabidopsis thaliana plants. We isolated 51 mutants with altered elemental profiles. One mutant contains a deletion in FRD3, a gene known to control iron-deficiency responses in A. thaliana. Based on the frequency of elemental profile mutations, we estimate 2-4% of the A. thaliana genome is involved in regulating the plant's nutrient and trace element content. These results demonstrate the utility of elemental profiling as a useful functional genomics tool.

Summary• We report on the second phase of a programme to select a relative of Arabidopsis thaliana for use in large-scale molecular genetic studies of nickel (Ni) and zinc (Zn) hyperaccumulation. We also report on the relatedness among Thlaspi caerulescens accessions and the utility of using O -acetyl-L -serine as a marker for Ni and Zn hyperaccumulation potential.• Twenty-seven new accessions of metal-accumulating species collected in the Czech Republic, France, Greece, Italy, Slovenia and the USA during Spring-Summer 2002 were evaluated.• The criteria established for selection were hyperaccumulation of metals (Ni and Zn); compact growth habit; reasonable time to flowering; production of ≥ 1000 seeds per plant; self-fertility; compact diploid genome; high sequence similarity to A. thaliana ; ≥ 0.1% transformation efficiency with easy selection.• We conclude that the best candidate identified in the first phase was the best candidate overall: T. caerulescens accession St Félix de Pallières.

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A simple and reproducible Agrobacterium-mediated transformation protocol for a recalcitrant legume plant, lentil (Lens culinaris M.) is reported. Application of wounding treatments and efficiencies of three Agrobacterium tumefaciens strains, EHA105, C58C1, and KYRT1 were compared for T-DNA delivery into lentil cotyledonary node tissues. KYRT1 was found to be on average 2.8-fold more efficient than both EHA105 and C58C1 for producing transient beta-glucuronidase (GUS) gene (gus) expression on cotyledonary petioles. Wounding of the explants, use of an optimized transformation protocol with the application of acetosyringone and vacuum infiltration treatments in addition to the application of a gradually intensifying selection regime played significant roles in enhancing transformation frequency. Lentil explants were transformed by inoculation with Agrobacterium tumefaciens strain, KYRT1 harboring a binary vector pTJK136 that carried neomycin phosphotransferase gene (npt-II) and an intron containing gusA gene on its T-DNA region. GUS-positive shoots were micrografted on lentil rootstocks. Transgenic lentil plants were produced with an overall transformation frequency of 2.3%. The presence of the transgene in the lentil genome was confirmed by GUS assay, PCR, RT-PCR and Southern hybridization. The transgenic shoots grafted on rootstocks were successfully transferred to soil and grown to maturity in the greenhouse. GUS activity was detected in vegetative and reproductive organs of T(0), T(1), T(2) and T(3) plants. PCR assays of T(1), T(2) and T(3) progenies confirmed the stable transmission of the transgene to the next generations.

A highly efficient Agrobacterium-mediated transformation system has been developed for lentils (Lens culinaris M) using vacuum infiltration of cotyledonary nodes and nodal segments with Agrobacterium suspension. This procedure exhibits distinct advantages over those previously reported in lentils, in that it uses vacuum infiltration enhancive force to introduce Agrobacterium suspension into the highly regenerable cotyledonary node meristems or nodal segments, which in turn rapidly produce transgenic shoots without an intermediate callus phase. The efficiency of the system has been investigated using GUS histochemical assays and PCR amplification which were evidencing integration of the trans genes and superiority of this system over conventional Agrobacterium mediated procedures that has been so far applied for lentil transformation.