Year: 2000
Type: dissertation
Abstract: Mesocarp of ripening avocado fruit incorporated label from [2-(14)C]mevalonolactone, \n[1-(14)C] acetic acid, [1-(14)C] glucose and [1 -(14)C] pyruvate into ABA, although \nincorporation from mevalonolactone was significantly higher. Inhibition of the \nmevalonate pathway at the HMGR level using mevastatin reduced incorporation from \nacetate and MVL, while increasing incorporation from pyruvate and glucose. The \ncarotenoid biosynthesis inhibitors AMO 1618 (inhibitor of lycopene cyclase) and \nfluridone (inhibitor of phytoene desaturase) both decreased incorporation of MVL \ninto ABA, while the plant growth regulators ancymidol (inhibitor of GA synthesis and \ncytochrome P450) and jasmonic acid (senescence stimulator reducing the carotenoid \ncontent of plants) both increased incorporation of MVL into ABA. Tungstate was \nfound to reduce incorporation from all four substrates into ABA, although more \nsignificantly from MVL and acetate. Further investigation revealed that the tungstate induced \ndecrease in MVL incorporation into ABA occurred concomitantly with \nincreased label incorporation into XAN. Cobalt, an inhibitor of ACC oxidase and \ntherefore of ethylene production, increased incorporation of MVL into ABA. Nickel \nhad a similar effect. Analysis of the methyl ester of ABA extracted from avocado \nmesocarp supplied with either [1-(13)C] acetic acid or [1-(13)C] glucose revealed \nincorporation of label from acetate consistent with formation of ABA via the \nacetate/mevalonate pathway whereas glucose was incorporated via the triose \nphosphate pathway of isopentenyl pyrophosphate formation. Methane, positive ion-chemical \nionisation-mass spectrometry of the cis, trans and all- trans isomers of ABA \nindicated more intense labelling of trans, trans-ABA, irrespective of substrate used. \nThese results indicate that trans, trans- and cis, trans-ABA are derived by different \npathways and that ABA is formed in avocado by both the mevalonate and non-mevalonate \npathways of isopentenyl diphosphate synthesis.
Author: Guillaume Maurel
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W804051218