Floral patterning and morphogenesis are controlled by many transcription factors including floral homeotic proteins, by which floral organ identity is determined. Recent studies have uncovered widespread regulation of transcription factors by microRNAs (miRNAs), ∼21-nucleotide non-coding RNAs that regulate protein-coding RNAs through transcript cleavage and/or translational inhibition. The regulation of the floral homeotic gene APETALA2 (AP2) by miR172 is crucial for normal Arabidopsis flower development and is likely to be conserved across plant species. Here we probe the activity of the AP2/miR172 regulatory circuit in a heterologous Solanaceae species, Nicotiana benthamiana. We generated transgenic N. benthamiana lines expressing Arabidopsis wild type AP2 (35S::AP2), miR172-resistant AP2 mutant (35S::AP2m3) and MIR172a-1 (35S::MIR172) under the control of the cauliflower mosaic virus 35S promoter. 35S::AP2m3 plants accumulated high levels of AP2 mRNA and protein and exhibited floral patterning defects that included proliferation of numerous petals, stamens and carpels indicating loss of floral determinacy. On the other hand, nearly all 35S::AP2 plants accumulated barely detectable levels of AP2 mRNA or protein and were essentially non-phenotypic. Overall, the data indicated that expression of the wild type Arabidopsis AP2 transgene was repressed at the mRNA level by an endogenous N. benthamiana miR172 homologue that could be detected using Arabidopsis miR172 probe. Interestingly, 35S::MIR172 plants had sepal-to-petal transformations and/or more sepals and petals, suggesting interference with N. benthamiana normal floral homeotic gene function in perianth organs. Our studies uncover the potential utility of the Arabidopsis AP2/miR172 system as a tool for manipulation of floral architecture and flowering time in non-model plants.
Bibliographical noteFunding Information:
Acknowledgements We are indebted to Dr Vicki Bowman Vance for support to S.M. during the revision of the manuscript. We are grateful to Drs Zora Svab and Pal Maliga for plant growth facilities; Dr Zora Svab for advice on tobacco tissue culture; Michael Petercsak for green house plant care; and Dr Hailing Jin for N. benthamiana cDNAs. We thank Drs Hailing Jin, Li Zhao, Bin Yu and Julien Curaba for helpful discussions, and Drs Vicki Bowman Vance and Beth Krizek for critical reading of the manuscript. S.M. was supported by a postdoctoral fellowship from the Waksman Institute at Rutgers University. The research was supported by a NIH grant (GM61146) to X.C.
All Science Journal Classification (ASJC) codes
- Agronomy and Crop Science
- Plant Science