Stress responses in alfalfa (Medicago sativa L). XXII. cDNA cloning and characterization of an elicitor-inducible isoflavone 7-O-methyltransferase

Stress responses in alfalfa (Medicago sativa L). XXII. cDNA cloning and characterization of an... Medicarpin, the major phytoalexin in alfalfa, is synthesized via the isoflavonoid branch of phenylpropanoid metabolism. The methyl group at the 9 position of medicarpin is generally accepted to arise via the methylation of the 4′ position (B-ring) of daidzein. Surprisingly, the isoflavone-O-methyltransferase (IOMT), which is induced along with other enzymes involved in medicarpin biosynthesis, methylates the A-ring 7-hydroxyl group of daidzein in vitro, a reaction that probably does not occur in vivo. Utilizing internal amino acid sequence information from purified alfalfa IOMT, we have isolated three full-length IOMT cDNA clones. A search of the protein databases revealed sequence similarities to O-methyltransferases from various sources. The highest match (50.5% identity) was found between IOMT8 and 6a-hydroxymaackiain 3-O-methyltransferase from Pisum sativum. The molecular weight of alfalfa IOMT expressed in Escherichia coli was similar to that of purified IOMT from alfalfa cell cultures (41 kDa by SDS-PAGE). The recombinant enzyme catalyzed the O-methylation of A-ring hydroxyl group(s) of isoflavones, and could also methylate the pterocarpan (+) 6a-hydroxymaackiain. Alfalfa contains multiple IOMT genes, and closely related sequences are present in the genomes of chickpea and cowpea, species that also produce B-ring methylated isoflavonoids in vivo. Northern blot analysis indicated that IOMT transcripts are rapidly induced following elicitation, prior to the increase in IOMT activity and medicarpin accumulation. The possible role of the isoflavone 7-OMT in the synthesis of formononetin in vivo is discussed. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Molecular Biology Springer Journals

Stress responses in alfalfa (Medicago sativa L). XXII. cDNA cloning and characterization of an elicitor-inducible isoflavone 7-O-methyltransferase

Loading next page...
 
/lp/springer_journal/stress-responses-in-alfalfa-medicago-sativa-l-xxii-cdna-cloning-and-yE19GO0km2
Publisher
Springer Journals
Copyright
Copyright © 1998 by Kluwer Academic Publishers
Subject
Life Sciences; Biochemistry, general; Plant Sciences; Plant Pathology
ISSN
0167-4412
eISSN
1573-5028
D.O.I.
10.1023/A:1005938121453
Publisher site
See Article on Publisher Site

Abstract

Medicarpin, the major phytoalexin in alfalfa, is synthesized via the isoflavonoid branch of phenylpropanoid metabolism. The methyl group at the 9 position of medicarpin is generally accepted to arise via the methylation of the 4′ position (B-ring) of daidzein. Surprisingly, the isoflavone-O-methyltransferase (IOMT), which is induced along with other enzymes involved in medicarpin biosynthesis, methylates the A-ring 7-hydroxyl group of daidzein in vitro, a reaction that probably does not occur in vivo. Utilizing internal amino acid sequence information from purified alfalfa IOMT, we have isolated three full-length IOMT cDNA clones. A search of the protein databases revealed sequence similarities to O-methyltransferases from various sources. The highest match (50.5% identity) was found between IOMT8 and 6a-hydroxymaackiain 3-O-methyltransferase from Pisum sativum. The molecular weight of alfalfa IOMT expressed in Escherichia coli was similar to that of purified IOMT from alfalfa cell cultures (41 kDa by SDS-PAGE). The recombinant enzyme catalyzed the O-methylation of A-ring hydroxyl group(s) of isoflavones, and could also methylate the pterocarpan (+) 6a-hydroxymaackiain. Alfalfa contains multiple IOMT genes, and closely related sequences are present in the genomes of chickpea and cowpea, species that also produce B-ring methylated isoflavonoids in vivo. Northern blot analysis indicated that IOMT transcripts are rapidly induced following elicitation, prior to the increase in IOMT activity and medicarpin accumulation. The possible role of the isoflavone 7-OMT in the synthesis of formononetin in vivo is discussed.

Journal

Plant Molecular BiologySpringer Journals

Published: Oct 6, 2004

References

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

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

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

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.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off