Ethylene responsive factor ERF110 mediates ethylene-regulated transcription of a sex determination-related orthologous gene in two Cucumis species

Abstract

In plants, unisexual flowers derived from developmental sex determination form separate stamens and pistils that facilitate cross pollination. In cucumber and melon, ethylene plays a key role in sex determination. Six sex determination-related genes have been identified in ethylene biosynthesis in these Cucumis species. The interactions among these genes are thought to involve ethylene signaling; however, the underlying mechanism of regulation remains unknown. In this study, hormone treatment and qPCR assays were used to confirm expression of these sex determination-related genes in cucumber and melon is ethylene sensitive. RNA-Seq analysis subsequently helped identify the ethylene responsive factor (ERF) gene, CsERF110, related to ethylene signaling and sex determination. CsERF110 and its melon ortholog, CmERF110, shared a conserved AP2/ERF domain and showed ethylene-sensitive expression. Yeast one-hybrid and ChIP-PCR assays further indicated that CsERF110 bound to at least two sites in the promoter fragment of CsACS11, while transient transformation analysis showed that CsERF110 and CmERF110 enhance CsACS11 and CmACS11 promoter activity, respectively. Taken together, these findings suggest that CsERF110 and CmERF110 respond to ethylene signaling, mediating ethylene-regulated transcription of CsACS11 and CmACS11 in cucumber and melon, respectively. Furthermore, the mechanism involved in its regulation is thought to be conserved in these two Cucumis species.

Gynoecy instability in cucumber (Cucumis sativus L.) is due to unequal crossover at the copy number variation-dependent Femaleness (F) locus

“…Among all three mutant lines, as compared with Gy14, the expression of both CsACS1 and CsACS2 was significantly down regulated, whereas no significant difference in expression was found for CsMYB among the four lines. In our previous study, transcriptome profiling for sex expression revealed no expression difference of the CsBCAT gene among the three mutant lines and Gy14 65 . These data suggest that expression level of both CsMYB and CsBCAT genes at the F locus may have no direct link with gynoecy expression in cucumber.…”

“…S2), but Shiber et al 71 did not detect any transcripts from this putative ORF thus ruling out the possibility that its product may be the F locus. In gynoecious plants (FF), the transcript level of CsACS1/G is much higher 38,65 . On the other hand.…”

Genetic and molecular bases of cucumber (Cucumis sativus L.) sex determination

“…The plant hormone ethylene plays an important role in sex determination in cucumber and counteracts the role of other hormones (Yin and Quinn 1995). Ethylene biosynthesis and its signaling pathway have been the subject of numerous studies that have proven the importance of this hormone in cucumber (Ando et al 2001a, b;Boualem et al 2008Boualem et al , 2009Sun et al 2010;Tao et al 2018;Wang et al 2010;Yamasaki et al 2003a, b).…”

“…Whether mRNA or protein or ethylene is the signal finally controlling sex is not known (Boualem et al 2015). Lastly, it was shown that ethylene signals are involved in the regulation of CsACS2 and CsACS11 at the transcriptional level involving CsERF110 (Tao et al 2018).…”

“…Taking into account the allelic relations, expression is dependent on CsACS11 (Chen et al 2016), whereby the M gene is not expressed in the line possessing genotypes: ffMMaa and both ffMMaa and ffmmaa (corresponding to androecious plants) (Kubicki 1969a). In monoecious and andromonoecious plants, male flowers are thought to result from nonexpression of CsACS11 and CsACS2, while female flowers develop because expression of CsACS11 could repress CsWIP1 (Boualem et al 2015, Tao et al 2018. Previous studies suggest that ethylene induces CsACS2 and inhibits CmWIP1 expression in cucumber and melon, respectively (Li et al 2012;Switzenberg et al 2014).…”