Correlation of metabolic fingerprints with differential growth responses of cold-inhibited salicylate mutants

Cold is a major environmental stress that determines the agricultural and horticultural productivity of particular geographical locations. Low temperatures impact meat as well as crop production, by limiting early-season growth of forage grass. Climate change adds a major uncertainty to future projections of world food production, with some current theories indicating cooling rather than warming of the UK climate. Last year we published a new discovery on the hormonal controls of plant growth at low temperature, finding mutants of the model plant Arabidopsis thaliana that showed much stronger than normal growth in controlled environments cooled to 5oC. This research was financed by the BBSRC Plant and Microbial Sciences Committee [Scott IM, Clarke SM, Wood JE, Mur LAJ (2004) Salicylate accumulation inhibits growth at chilling temperature in Arabidopsis. Plant Physiology 135:1040-1049]. The present proposal is a follow-up, which capitalises on the launch of the BBSRC's Plant and Microbial Metabolomics (MeT-RO) Centre, and seeks to use these facilities to analyse a wide spectrum of the low molecular weight biochemicals in plant cells, to produce so-called 'metabolic fingerprints'. Our preliminary studies show that metabolic fingerprints can be used to classify Arabidopsis mutants according to their propensity for growth at low temperature. The MeT-RO Centre service will produce detailed and informative metabolic fingerprints from which we will learn a great deal about the cellular states that determine the ability of plants to grow more strongly in the cold.

We discovered in a recent BBSRC PMS project that the salicylic acid (SA) contents and responses of Arabidopsis genotypes are powerful determinants of the propensity for growth at chilling temperature (5oC). We have since obtained preliminary evidence, with a high-throughput screening analysis in conjunction with multivariate chemometrics, to support the hypothesis that the metabolic fingerprints of these genotypes can be correlated with their differential 5oC growth responses. We now propose to use the MeT-RO NMR service to obtain comprehensive and well characterised metabolic fingerprints of the SA-related genotypes NahG (SA-degradation by bacterial transgene), eds5 (low endogenous SA), sid2 (SA biosynthesis mutant), npr1 (well characterised SA-signal transduction mutant), and cpr1 (elevated endogenous SA), along with their common wild-type Col-0. We will use the MeT-RO data mining service to find metabolite patterns within the fingerprints that correlate with the 5oC growth responses. Similar analyses will be performed at 23oC to confirm that metabolites correlate with 5oC growth rather than genotype, and to provide further exploration of the 'temperature-stress' metabolome recently described by others in wild-type Arabidopsis. This methodologically innovative proposal will yield important insights into the metabolic states that correlate with the ability of plants to grow more strongly in the cold.