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It is well established that ethylene promotes female flower development in cucumber. However, little is known about how the gaseous hormone selectively affects female flowers, and what mechanism it uses. Previously, we found organ-specific DNA damage in the primordial anther of female cucumber flowers. This finding led to a hypothesis that ethylene might promote female flower development via the organ-specific induction of DNA damage in primordial anthers. In this study, we tested this hypothesis first by demonstrating ethylene induction of DNA damage via the ethylene signaling pathway using cucumber protoplasts. Then, using representative component genes of the ethylene signaling pathway as probes, we found that one of the ethylene receptors, CsETR1, was temporally and spatially downregulated in the stamens of stage-6 female cucumber flowers, especially along with the increase of the nodes. Furthermore, by constructing transgenic Arabidopsis plants with organ-specific expression of antisense CsETR1 under the control of an AP3 promoter to downregulate ETR1 expression in the stamens, we generated Arabidopsis ‘female flowers’, in which the abnormal stamens mimic those of female cucumber flowers. Our data suggest that ethylene perception is involved in the arrest of stamen development in female cucumber flowers through the induction of DNA damage. This opens up a novel perspective and approach to solve the half-century-long puzzle of how gaseous ethylene selectively promotes female flowers in the monoecious cucumber plant. [ABSTRACT FROM AUTHOR]

• Abscisic acid (ABA) is known to function in plant stress responses and seed dormancy, and much is known about its detailed mechanisms of signal transduction. Recent studies suggest that this hormone may also play important roles in sugar signaling and assimilate distribution during fruit development. However, little is known about the role of ABA in actively growing or differentiating fruits and other plant organs or tissues. • To explore whether ABA functions during the early development of reproductive organs, we carried out ABA immunolocalization using monoclonal antibodies. The specific ABA accumulation pattern was verified by gas chromatography–mass spectrometry (GC-MS). • ABA was not only detected in primordial cells of flower organs, but was also detected in nursing cells (e.g. tapetum and integuments), which function in supplying nutrition for germ cell development. • These findings suggest that, in addition to its well-known function as a ‘negative hormone’, ABA may play some ‘positive’ roles during plant development, including possible involvement in the regulation of assimilate distribution. [ABSTRACT FROM AUTHOR]