T. Thykjaer et al., ORGANIZATION AND EXPRESSION OF GENES IN THE GENOMIC REGION SURROUNDING THE GLUTAMINE-SYNTHETASE GENE GLN1 FROM LOTUS-JAPONICUS, MGG. Molecular & general genetics, 255(6), 1997, pp. 628-636
The diploid Lotus japonicus was previously suggested as a model for th
e legume plant family. We present here the nucleotide sequence and the
derived gene organization of a small part of the genome in this model
plant. Two functional genes with the same transcriptional orientation
were identified within the 23 326-bp genomic region analysed. The LjG
ln1 gene encodes a cytosolic glutamine synthetase and the LjKrm (Kines
in repeat motif) gene encodes a polypeptide with similarity to a repea
ted motif present in the microtubule-associated kinesin light chain pr
otein. Transcripts of the glutamine synthetase gene are found primaril
y in roots and root nodules, while transcripts of the Krm gene are fou
nd in roots, root nodules and leaves, In the region between Gln1 and K
rm, the presence of a third gene, Pge1, was suggested by analysis with
the Grail exon recognition program. Upstream of the Gln1 gene a segme
nt carrying two apparently non-functional, fragmented copia-like retro
elements, dRtp1 and dRtp2, was identified. Sequence similarity to reve
rse transcriptase- and RNaseH-coding regions defined the defective ret
roelements dRtp1 and dRtp2 within this segment. Terminal repeats were
not found but three different sets of short direct repeats are located
adjacent to the dRtp1 element. The three genes and the incomplete ret
roelements occupy most of the analysed DNA, leaving approximately one-
fifth of the chromosome fragment without recognisable genome constitue
nts.