Effect of modified endogenous ethylene production on sex expression, bisexual flower development and fruit production in melon (Cucumis melo L.)

Abstract

Members of the Cucurbitaceae family display a range of sexual phenotypes including various combinations of male, female, or bisexual flowers. Ethylene appears to be a key hormone regulating the sex determination process. Application of ethylene, or inhibition of ethylene action, increases or decreases the number of pistil-bearing buds, respectively. Elevated levels of ethylene production and expression of genes for ethylene biosynthesis, have been correlated with pistillate flower production. In this study, we sought to determine the effect of modified endogenous ethylene production on sex expression by constitutively expressing ACS (1-aminocyclopropane-1-carboxylate synthase), the first committed enzyme for ethylene biosynthesis, in transgenic melons (Cucumis melo L.). Most melon genotypes are andromonoecious, where an initial phase of male flowers is followed by a mixture of bisexual and male flowers. ACS melon plants showed increased ethylene production by leaves and flower buds, and increased femaleness as measured by earlier and increased number of bisexual buds. ACS melons also had earlier and increased number of bisexual buds that matured to anthesis, suggesting that ethylene is important not only for sex determination, but also for development of the bisexual bud to maturity. Field studies showed that ACS melons had earlier mature bisexual flowers, earlier fruit set, and increased number of fruit set on closely spaced nodes on the main stem. These results provide a direct demonstration of the importance of endogenous ethylene production for female reproductive processes in melon.

Stamen development in Arabidopsis is arrested by organ-specific overexpression of a cucumber ethylene synthesis gene CsACO2

“…Our Wndings were consistent with the reports that increased endogenous ethylene production enhanced femaleness in transgenic melon (Cucumis melo L.), indicated by studies with 35S promoter driven ACS genes (Papadopoulou et al 2005) and a CRC promoter driven dominant negative etr1 gene (Little et al 2007). Papadopoulou et al (2005) and Little et al (2007) indicated ethylene eVects on carpel development in transgenic melon.…”

“…Papadopoulou et al (2005) and Little et al (2007) indicated ethylene eVects on carpel development in transgenic melon. However, we found no eVects of increased ethylene production on carpel development in transgenic P AP3 : CsACO2 Arabidopsis.…”

The effect of growth regulators on sex expression in melon (Cucumis melo L.)

“…Growth regulators or phytohormones, especially ethylene / ethrel (Papadopoulou et al 2005, Manzano et al 2008 and gibberellic acid, i.e.GA 3 (Thomas 2008), are mostly used to modify sex expression in melon.…”

“…Several investigations have shown that phytohormones are involved in changes of flower type, number and ratio of flowers of different sex types, modifications of flowering time and of other traits related to sex expression (Noguera et al 2005, Papadopoulou et al 2005, Stankovic et al 2005, Yamasaki et al 2005, Little et al 2007, Boualem et al 2008, Ouzounidou et al 2008, Martin et al 2009). Most of these studies were performed in cucumber, the model plant for studying sex expression in Cucurbitaceae.…”

Role of ethylene receptors during senescence and ripening in horticultural crops

“…Significance of endogenous ethylene production for pistillate flower development has been demonstrated in melon by Papadopoulou et al (2005). 146 Constitutive overexpression of ethylene biosynthetic gene, ACS resulted in enhanced endogenous ethylene accelerating bisexual flower initiation, development of mature bisexual flowers and fruit set in melon.…”