Involvement of Ethylene Biosynthesis and Signalling in the Transition from Male to Female Flowering in the Monoecious Cucurbita pepo

• Published in: Journal of plant growth regulation 2013-12, Vol.32 (4), p.789-798
• Main Authors: Manzano, Susana, Martínez, Cecilia, Megías, Zoraida, Garrido, Dolores, Jamilena, Manuel
• Format: Article
• Language: English
• Subjects: Agriculture; Biomedical and Life Sciences; Biosynthesis; Buds; cucumbers; Cucumis sativus; Cucurbita pepo; ethylene; ethylene production; female flowers; flowering; Flowers; genes; inbred lines; Life Sciences; Plant Anatomy/Development; Plant Physiology; Plant Sciences; receptors; sex determination
• ISSN: 0721-7595; 1435-8107
• DOI: 10.1007/s00344-013-9344-6

It is well established that ethylene is the main hormonal regulator of sexual expression in the Cucurbitaceae family, controlling not only the sexual fate of individual floral buds, but also the female flower transition, that is, the time at which the first female flower appears and therefore the number of female flowers per plant. Although sex determination of individual flower buds is known to be controlled by specific ethylene biosynthesis ACS genes in melon and cucumber, the role of ethylene genes in the control of the transition to female flowering is still unknown. We have identified two contrasting monoecious inbred lines of Cucurbita pepo, Bolognese (Bog) and Vegetable spaghetti (Veg), which differ in female flower transition but not in flower development. In Bog, which is very sensitive to ethylene, the transition to female flowering is very early, whereas in Veg, which is much less sensitive to ethylene, the transition occurs much later. In this article we compare the production of ethylene and the expression profiles of seven genes involved in the biosynthesis, perception, and signalling of ethylene in the two contrasting lines. Bog, with earlier female flower transition, showed higher ethylene production and CpACO1 expression in the apex at an earlier stage of plant development, when Bog is already producing female flowers, but Veg has not transitioned to female flowering yet. Moreover, the expression of the ethylene receptor and CTR-like genes in the apex of Veg and Bog plants indicates that these genes negatively regulate female flower transition during the earlier stages of plant development. The earlier transition to female flowering in Bog is not only associated with a higher production of ethylene in the apex but also with a premature decline of ethylene negative regulators (receptors and CTR-like) in the apex of the plant. These results provide the basis for a model that explains the regulation of female flowering transition in monoecious cucurbits.