Gas chromatography-mass spectrometry based metabolite profiling of biological samples is rapidly becoming one of the cornerstones of functional genomics and systems biology. Thus, the technology needs to be available to many laboratories and open exchange of information is required such as those achieved for transcript and protein data. The key-step in metabolite profiling is the unambiguous identification of metabolites in highly complex metabolite preparations with composite structure. Collections of mass spectra, which comprise frequently observed identified and non-identified metabolites, represent the most effective means to pool the identification efforts currently performed in many laboratories around the world. Here, we describe a platform for mass spectral and retention time index libraries that will enable this process (MSRI; www.csbdb.mpimpgolm.mpg.de/gmd.html). This resource should ameliorate many of the problems that each laboratory will face both for the initial establishment of metabolome analysis and for its maintenance at a constant sample throughput.

Boron (B) is an essential micronutrient that affects plant growth at either deficient or toxic concentrations in soil. The aim of this work was to investigate the adaptation of barley (Hordeum vulgare) plants to toxic B levels and to increase our understanding of B toxicity tolerance mechanisms. We used a metabolomics approach to compare metabolite profiles in root and leaf tissues of an intolerant, commercial cultivar (cv Clipper) and a B-tolerant Algerian landrace (cv Sahara). After exposure to elevated B (200 and 1,000 mM), the number and amplitude of metabolite changes in roots was greater in Clipper than in Sahara. In contrast, leaf metabolites of both cultivars only responded following 1,000 mM treatment, at which B toxicity symptoms (necrosis) were visible. In addition, metabolite levels were dramatically altered in the tips of leaves of the sensitive cultivar Clipper after growth in 1,000 mM B compared to those of Sahara. This correlates with a gradual accumulation of B from leaf base to tip in B-intolerant cultivars. Overall, there were always greater differences between tissue types (roots and leaves) than between the two cultivars. This work has provided insights into metabolic differences of two genetically distinct barley cultivars and information about how they respond metabolically to increasing B levels.Boron (B) is an essential micronutrient for vascular plants. However, when B is present at high concentrations in the soil or ground water, plant growth and reproduction can be affected by B toxicity. B toxicity has been recognized as an important problem limiting crop production in the low rainfall and on highly alkaline and saline soils in regions of Australia, West Asia, and North Africa. Because soil amelioration is impractical, the development of B-tolerant cultivars is a rational solution to the problem.B freely diffuses into the roots as boric acid [B(OH) 3 ; pK a 5 9.25] and accumulates in the cytoplasm as the borate anion [B(OH) 4 2 ] due to pH-dependent interconversion. An inability to exclude B from the roots results in high B concentrations in the tissue. B phytotoxicity manifests itself in a broad range of physiological effects, including decreased shoot and root growth, root cell division and RNA content, reduced leaf chlorophyll, lower photosynthetic rates and stomatal conductance, and reduced levels of lignin and suberin (for review, see Nable et al., 1997). Leaf symptoms of toxicity in barley (Hordeum vulgare) are characterized by interveinal chlorotic and/or necrotic patches, generally at the margins and tips of older leaves. This reflects the accumulation of B at the end of the transpiration stream (Nable et al., 1997). Following long-term exposure to high B concentrations in the soil, overall vegetative plant growth is retarded and this leads to either a reduction in or a complete lack of seed set.B is also an essential nutrient, although its role in plant growth, development, and metabolism remains to be clarified. Originally, B was thought to be essentially immobile in the ...