Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Abstract Only
Publication Acceptance Date: 2/6/2015
Publication Date: 5/2/2015
Citation: Wagner, T.A., Liu, J., Puckhaber, L.S., Bell, A.A., Stipanovic, R.D. 2015. RNAi blockage of desoxyhemigossypol-6-OMT decreases the amounts of methylated sesquiterpenoids in transgenic cotton roots [abstract]. 2015 Beltwide Cotton Conferences, January 5-7, 2015, San Antonio, Texas. CDROM.
Technical Abstract: After pathogen attack, plants produce compounds, called phytoalexins that are toxic to microorganisms. In the case of the cotton plant, these include desoxyhemigossypol (dHG), desoxyhemigossypol-6-methyl ether (dMHG), hemigossypol (HG), and hemigossypol-6-methyl ether (MHG), written in the order of toxicity. Non-methylated compounds are more toxic to fungi than their methylated counterparts. We previously identified, cloned and sequenced the desoxyhemigossypol-6-O-methyltransferase (dHG-6-OMT) gene from Gossypium barbadense that is responsible for the conversion of dHG to dMHG. Our objective is to suppress expression of dHG-6-OMT using an RNAi construct, and determine the disease resistance of these RNAi lines. Eight plants from 6 independent transformation events were generated. Analysis of a small amount of roots from these healthy plants indicated that the methyl transferase was suppressed. Between 32 and 45% of total sesquiterpenoids are methylated in wild type roots. In contrast, only 0 to 20% of the total sesquiterpenoids are methylated in the roots of T0 RNAi plants. Healthy roots from the F1 progeny of one of these lines have been tested, and the RNAi transgene co-segregates with reduced root sesquiterpenoid methylation in the F1 progeny. 1.4% of sesquiterpenoids are methylated in the RNAi-containing plants compared to 27.2% methylation in the WT siblings. The loss of methylated sesquiterpenoids in the roots of RNAi-containing plants leads to a reduction in total terpenoids (68% of WT levels). In the future, the RNAi-containing lines will be tested for pathogen resistance, and the roots will be analyzed for increased levels of sesquiterpenoids compared to the WT.