| Autor: |
Waterhouse RN; Department of Agricultural Sciences, University of Bristol, UK., Smyth AJ, Massonneau A, Prosser IM, Clarkson DT |
| Jazyk: |
angličtina |
| Zdroj: |
Plant molecular biology [Plant Mol Biol] 1996 Mar; Vol. 30 (5), pp. 883-97. |
| DOI: |
10.1007/BF00020801 |
| Abstrakt: |
Two cDNA clones, LJAS1 and LJAS2, encoding different asparagine synthetases (AS) have been identified and sequenced and their expression in Lotus japonicus characterised. Analysis of predicted amino acid sequences indicted a high level of identity with other plant AS sequences. No other AS genes were detected in the L. japonicus genome. LJAS1 gene expression was found to be root-enhanced and lower levels of transcript were also identified in photosynthetic tissues. In contrast, LJAS2 gene expression was root-specific. These patterns of AS gene expression are different from those seen in pea. AS gene expression was monitored throughout a 16 h light/8 h dark day, under nitrate-sufficient conditions. Neither transcript showed the dark-enhanced accumulation patterns previously reported for other plant AS genes. To evaluate AS activity, the molecular dynamics of asparagine synthesis were examined in vivo using 15N-ammonium labelling. A constant rate of asparagine synthesis in the roots was observed. Asparagine was the most predominant amino-component of the xylem sap and became labelled at a slightly slower rate than the asparagine in the roots, indicating that most root asparagine was located in a cytoplasmic 'transport' pool rather than in a vacuolar 'storage' pool. The steady-state mRNA levels and the 15N-labelling data suggest that light regulation of AS gene expression is not a factor controlling N-assimilation in L. japonicus roots during stable growth in N-sufficient conditions. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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