| Description: | Plants co-regulate carbon and nitrogen assimilation, metabolism, transport and storage by sensing the concentration of certain metabolites. In the presence of methylamine (MA), an ammonium analog, the growth of Arabidopsis thaliana is markedly reduced because methyl-glutamine accumulates. This metabolite signals N sufficiency to plant cells and metabolism is altered to favour C assimilation, transport and storage. A hypersensitive mutant was isolated by selection on media containing methylamine. The mutants segregated for green:chlorosis (3:1) and for sensitivity to exogenous ammonium chloride (1:2:1). The mutation altered the enzyme activity of GS, NR and GDH and was dominant, overdominant and codominant in effect respectively. Transcription of several genes was altered, the lesion eliminated the ability of GDH NR ASN and GS to respond to exogenous C and N sources, glutamine and sucrose. Therefore, we conclude the underlying gene participates in glutamine sensing and regulation. The gene underlying the mutation has been isolated in from a BAC library and will be identified by complementation. Gene expression networks in all cases appear to confer hypersensitivity but global analysis of their expression patterns has not been possible until recently. Understanding the nature of gene expression waves of Arabidopsis will allow comparison with the networks underlying glutamine sensing. The identification of common gene homologues between this model system and crop plants, particularly soybean, will also be of import. We will generate probe cDNA from mRNA extracted from wild type Arabidopsis thaliana cv. Columbia seedlings at 14-DAP. Alterations in gene expression encompassing this period must generate the ability to survive glutamine miss-sensing. The analysis will allow the classification of genes within Arabidopsis relative to glutamine sensing. Plants are grown to maturity under conditions of light, temperature and humidity that promote normal development (22 C, 20 hr photoperiod). Synchronously growing plants were selected for tissue collection. Sufficient whole seedlings to purify ten micrograms of mRNA at 14-DAP were collected. Aliquots of seedlings were reserved for probe duplication, quantitative PCR confirmation of expression profiles and proteomics (2D gels, enzyme assay, Western hybridization). |
NASCArrays Information at The BAR
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