| The phytohormone ethylene regulates multiple aspects of plant growth and development. Ethylene influences the flower opening in roses by repressing the expansion of abaxial sub-epidermis cells in rose petals. However, the molecular mechanism underlying this process is not very clear. Here, we reported that ethylene-regulated cell expansion in rose petals was partly mediated by a growth repressor RhGAIl. Ethylene induced the expression of RhGA11, while ethylene inhibitor1-MCP suppressed its expression. And, silencing of RhETRs in rose petals increased the expression of RhGAI1. In transgenic Arabidopsis ein2mutant seedlings carrying the proRhGAI1::GUS, interruption of ethylene signaling changed the expression pattern of RhGAI1. Further, RhEIN3-3strongly induces the promoter activity of RhGAIl in Arabidopsis protoplasts. By EMSA assay, we found that RhEIN3-3could bind to the promoter of RhGAI1, which indicated that RhGAI1was a direct target of RhEIN3-3. We also found that RhGAI1regulated the expansion of petal cells. Over-expression of RhGAIl restrained the expansion of abaxial sub-epidermis cells in Arabidopsis petals, while silencing of RhGAI1promoted the expansion of abaxial sub-epidermis cells in rose petals. What’s more, RhGAI1regulated the expression of a couple of cell expansion-related genes, which were possibly responsible for inhibition of petal expansion by RhGAIl. The promoter activity of RhCesA2is intensively repressed by RhGAIl. By EMSA assay, we found that RhGAIl could bind to the promoter of RhCesA2, which indicated that RhCesA2was a direct target of RhGAIl. Taken together, these results demonstrated that the expression of RhGAI1is induced by ethylene, and RhGAIl restrained the expansion of rose petals partly by regulating the expression of several cell expansion-related genes. This work uncovers the transcriptional regulation of RhGAI1by ethylene and provides a better understanding of how ethylene regulates petal expansion in roses. |
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