The putrescine N-methyltransferase (PMT) cDNA clone previously isolated from tobacco encodes a spermidine synthase-like protein with an 11 amino acid element repeated four times in tandem at the amino terminus. Genomic Southern blot analyses indicated that this N-terminal repeat array is found in tobacco PMTs but absent in Hyoscyamus and Atropa PMTs. A truncated tobacco PMT in which this repeat array was entirely removed still retained full enzymatic activity when expressed in Escherichia coli. Three PMT genes (NsPMT1, NsPMT2, NsPMT3) isolated from Nicotiana sylvestris encode two, five, and nine tandem repeats, respectively, in the first exon, but otherwise encode highly conserved proteins. Analysis of PCR fragments amplified from the genomes of N. tabacum and its two probable progenitors shows that one of the nine repeat elements in NsPMT3 was precisely deleted in the corresponding N. tabacum gene. These results indicate that direct tandem repeats of a 33 bp sequence that encodes 11 amino acids of no obvious function were added to the ancestral Nicotiana PMT gene, and that the tandem repetition was genetically very unstable, contracting or expanding during evolution of the Nicotiana species.
Plant Molecular Biology – Springer Journals
Published: Oct 6, 2004
It’s your single place to instantly
discover and read the research
that matters to you.
Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.
All for just $49/month
Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly
Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.
Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.
Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.
All the latest content is available, no embargo periods.
“Hi guys, I cannot tell you how much I love this resource. Incredible. I really believe you've hit the nail on the head with this site in regards to solving the research-purchase issue.”Daniel C.
“Whoa! It’s like Spotify but for academic articles.”@Phil_Robichaud
“I must say, @deepdyve is a fabulous solution to the independent researcher's problem of #access to #information.”@deepthiw
“My last article couldn't be possible without the platform @deepdyve that makes journal papers cheaper.”@JoseServera