Correlation between development of female flower buds and expression of the CS-ACS2 gene in cucumber plants

Abstract

Ethylene plays a key role in sex determination of cucumber flowers. Gynoecious cucumber shoots produce more ethylene than monoecious shoots. Because monoecious cucumbers produce both male and female flower buds in the shoot apex and because the relative proportions of male and female flowers vary due to growing conditions, the question arises as to whether the regulation of ethylene biosynthesis in each flower bud determines the sex of the flower. Therefore, the expression of a 1-aminocyclopropane-1-carboxylic acid synthase gene, CS-ACS2, was examined in cucumber flower buds at different stages of development. The results revealed that CS-ACS2 mRNA began to accumulate just beneath the pistil primordia of flower buds at the bisexual stage, but was not detected prior to the formation of the pistil primordia. In buds determined to develop as female flowers, CS-ACS2 mRNA continued to accumulate in the central region of the developing ovary where ovules and placenta form. In gynoecious cucumber plants that produce only female flowers, accumulation of CS-ACS2 mRNA was detected in all flower buds at the bisexual stage and at later developmental stages. In monoecious cucumber, flower buds situated on some nodes accumulated CS-ACS2 mRNA, but others did not. The proportion of male and female flowers in monoecious cucumbers varied depending on the growth conditions, but was correlated with changes in accumulation of CS-ACS2 mRNA in flower buds. These results demonstrate that CS-ACS2-mediated biosynthesis of ethylene in individual flower buds is associated with the differentiation and development of female flowers.

Bird–nest puzzle: can the study of unisexual flowers such as cucumber solve the problem of plant sex determination?

“…This result is consistent with the high frequency of M gene mutations in cucumber, as well as the equivalent A gene in melon (Boualem et al 2008Li et al 2009), and the proposed recent duplication of the F gene (Knopf and Trebitsh 2006). As the M gene is preferentially expressed in carpels (Saito et al 2007), the role of ethylene in the inhibition of stamen development can be narrowed down to how the expression pattern of the M gene evolved. Three lines of recent evidence are worth noting with regard to this question.…”

“…While TS1 plays a role in sex determination by affecting JA signaling (Acosta et al 2009), TS4 affects sex determination by targeting IDS1 in maize (Chuck et al 2007). It is known that the cucumber M gene is specifically expressed in carpels (Saito et al 2007) and that the melon A gene expression is indirectly repressed by the transcription factor CmWIP1 (Martin et al 2009). However, additional details of unisexual flower development in these plants remain elusive.…”

Expression pattern of the pre-prothaumatin II gene under the control of the CaMV 35S promoter in transgenic cucumber (Cucumis sativus L.) flower buds and fruits

“…Cucumber (Cucumis sativus L.) is a monoecious plant in which female sex expression (gynoecy) is controlled by the Female (F) locus, which can be modified by other sex-determining genes as well as environmental and hormonal factors (Saito et al 2007). …”

A Preliminary Study for Cucurbita moschata Duchesne (Loche) Crop Production under the Hydroponic Dutch Bucket System

“…However, flowering and its ratio can me modulates by phytohormones in cucurbits [32] which could be tested as a cheaper alternative. Future attempts in hydroponic "Loche" production should consider external application of ethylene or ethylene-releasing compounds in well-stablished transplants as for melon [33] and cucumber [34] and/or direct modulation of any of the genes involved in sex determination for cucurbits already identified [35,36]. The former only probable if the parthenocarpic origin of the fruit is validated [6] since no male flowers might be obtained.…”