Submitted to: Plant Signaling and Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2008
Publication Date: 2/25/2008
Citation: Baerson, S.R., Rimando, A.M., Pan, Z. 2008. Probing Allelochemical Biosynthesis in Sorghum Root Hairs. Plant Signaling and Behavior. 3(9):667-670. Interpretive Summary: In this manuscript we provide additional perspectives, commentary, and data concerning our unit’s research on identifying sequences expressed in root hair cells in sorghum and identifying a key enzyme which we call SbOMT3. SbOMT3 is an O-methyltransferase enzyme proposed to participate in the synthesis of the chemical sorgoleone which is manufactured in root hair cells of the sorghum plant. We also provide new data that shows this chemical is probably only produced within one genus of the plant family Poacea (grass family), namely the genus sorghum. We also provide the gene expression patterns for all O-methyltransferase genes which we found to be expressed in root hair cells in our data set, and point out that one sequence that we have not yet tested appears to be similar to SbOMT3, and might have the same function. We also discuss new data available from the sorghum genome project showing that SbOMT3 exists in three copies that are found very close together in the sorghum genome. These observations suggest to us that more than one gene may actually be involved in the O-methyltransferase activity associated with the synthesis of sorgoleone.
Technical Abstract: Allelopathic interaction between plants is thought to involve the release of phytotoxic allelochemicals by one species, thus inhibiting the growth of neighboring species in competition for limited resources. Sorgoleone represents one of the more potent allelochemicals characterized to date, and its prolific production in root hair cells of Sorghum spp. has made the investigation of its biosynthetic pathway an attractive target for functional genomics. An EST dataset comprised of 5,468 sequences generated from root hair cells isolated from S. bicolor genotype BTx623 was recently made publicly available, and has been mined for sequences potentially encoding enzymes involved in sorgoleone biosynthesis. These efforts have led to the identification of a 5-n-alk(en)ylresorcinol utilizing O-methyltransferase, designated SbOMT3, likely involved in the O-methylation of the 5-n-pentadecatrienyl resorcinol biosynthetic precursor of sorgoleone in planta.