N form–dependent growth retardation of Arabidopsis thaliana seedlings as revealed from physiological and microarray studies |
| |
Authors: | Anne Hoffmann Sabine Milde Christine Desel Anja Hümpel Hartmut Kaiser Enno Hammes Mirva Piippo Arto Soitamo Eva‐Mari Aro Jóska Gerendás Burkhard Sattelmacher Ulf‐Peter Hansen |
| |
Institution: | 1. Center for Biochemistry and Molecular Biology, Christian‐Albrechts‐University, Leibnizstr. 11, 24098 Kiel, Germany;2. Zoological Institute, Christian‐Albrechts‐University, Olshausenstrasse 40, 24098 Kiel, Germany;3. Botanical Institute, Christian‐Albrechts‐University, Am Botanischen Garten 9, 24098 Kiel, Germany;4. Department of Biology, University of Turku, Fi‐20014 Turku, Finland;5. Institute for Plant Nutrition and Soil Science, Christian‐Albrechts‐University, Hermann‐Rodewald‐Str. 4, 24098 Kiel, Germany |
| |
Abstract: | Ammonium (NH ) nutrition causes retardation of growth in many plant species. In Arabidopsis grown with NH as the sole N source, growth retardation occurs already at early stages before photosynthesis has come to its full power. In order to describe the peculiarities of these retarded plants, they were compared with nitrate (NO )‐grown plants of the same age of 15 d. Photosynthetic activity as measured by CO2 uptake per unit chlorophyll is half as high in NH ‐grown seedlings as in NO ‐grown ones. This finding is confirmed by the analysis of chlorophyll fluorescence. Chloroplasts of NO ‐grown, but not of NH ‐grown, seedlings show starch deposits after 5 h of illumination with 40 μmol m–2 s–1. Gene‐expression analysis based on cDNA microarray and on Northern blots provide a clue about the biochemical background. After the first 2 weeks of growth, it seems that NO ‐grown seedlings subsist mainly on normal photosynthesis, whereas NH ‐grown seedlings still use lipids from the seeds stored in oleosomes. Corresponding to this observation, the mRNAs for enzymes of β‐oxidation are more strongly expressed in NH ‐grown seedlings. Different carbohydrate sources for sucrose synthesis are indicated by different gene expression. Higher gene expression of fructose bisphosphate aldolase (cytosolic isoform) in NO ‐grown seedlings indicates the dependence on photosynthesis, whereas a higher gene expression of PEP carboxykinase in NH ‐grown seedlings points to a prominent role of β‐oxidation of storage lipids still present. |
| |
Keywords: | β ‐oxidation gene expression N nutrition photosynthetic efficiency sucrose synthesis |
|
|