|Macnish, Andrew -|
|Negre-Zakharov, Florence -|
|Reid, Michael -|
Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 26, 2010
Publication Date: June 4, 2010
Citation: Macnish, A.J., Jiang, C., Negre-Zakharov, F., Reid, M.S. 2010. Physiological and molecular changes during opening and senescence of Nicotiana mutabilis flowers. Plant Science. 179:267-272. Technical Abstract: The flowers of Nicotiana mutabilis, a tobacco species recently discovered in southern Brazil, have petals that undergo a striking colour change from white through pink to red as they open and senesce over a typical 7-d lifespan. Colouration in petals was associated with an increase in chalcone synthase (CHS) gene expression and a substantial rise in the anthocyanin content. It was also initially accompanied by up-regulation of 1- aminocyclopropane-1-carboxylic acid oxidase (ACO) transcripts and consequently by elevated rates of ethylene production at the onset of petal wilting. Emission of the fragrant monoterpenoid volatiles 1,8-cineole, linalool and terpineol also increased as petals developed pink colouration. The increase in volatile emission was preceded by a rise in monoterpene synthase (MTS) gene expression in petals. Transcripts of a homolog of SAG12, a senescence-associated gene encoding a cysteine protease, began to accumulate in petals 3 d prior to visible wilting as the colour change advanced and ethylene production increased. Exposure of newly opened white flowers to 1 µl l-1 ethylene accelerated petal colouration, wilting, and induction of SAG12 expression by ca. 1 d while treatment with 500 nl l-1 1-methylcyclopropene (1-MCP), an inhibitor of ethylene action, retarded these processes. The numerous genetic and experimental tools available for tobacco can readily be applied to this close relative, which therefore provides an interesting new model for studying ethylene-mediated flower senescence.