Heterosis in the freezing tolerance of Arabidopsis thaliana (L.)Heynh
We investigated heterosis in freezing tolerance of 24 reciprocal Arabidopsis-crosses with C24 and Col-0. The underlying genetic mechanisms of Heterosis, the enhancement of F1-hybrids in comparison to their homozygous parents, are unknown. Different mechanisms such as dominance, overdominance or epistasis are suggested. Parental freezing tolerance (LT50) was shown to correlate with the original habitat temperature. Besides the LT50, proline and sugar contents (glc, fru, suc, raf) have been measured on non-acclimated and cold-acclimated plants. Metabolite profiling and flavonoid measurements revealed significant stronger heterosis in C24- than in Col-crosses. Heterosis increases after cold acclimation. Freezing tolerance clearly correlate with the contents of sugars, proline and several flavonols, as well as the strength of heterosis in freezing tolerance with the metabolite content. GCMS-measurement confirmed these results. Fourty metabolites, of which many significantly correlate with LT50 and/or with heterosis in metabolite content and in LT50, were found. Six of these are important compounds in the TCA-cycle. Changes in flux rates of the TCA-cycle could be connected to Heterosis for the first time. Negative correlation between Heterosis in freezing tolerance and metabolite accumulation, points to a role of parts of the cycle in crosses and to a change of flux rates.