Determining the roles and regulation of MIRNA156 genes in reproductive development of annual and perennial Brassicaceae species
Final Report Abstract
Most plants flower in spring after exposure to winter temperatures and as the day length becomes longer. However, in addition to these environmental cues, flowering is regulated by internal developmental signals. For example, many plants do not flower when they are young, in the juvenile phase, but only after aging and reaching the adult phase. Work in the model species Arabidopsis thaliana first suggested that this age signal is regulated by two families of small RNA molecules that repress the activity of transcription factors that promote or repress flowering. These RNA molecules are called microRNA156/7 and microRNA172. These microRNAs (miRNAs) are encoded by many genes that can be active at different times and in different tissues during plant development. In A. thaliana, miR156/7 are encoded by twelve genes and miR172 is encoded by five genes. The major aim of this project was to analyse the functions of these genes using advances in CRISPR-cas9 gene editing, and to make fluorescent protein fusions in each gene so that we can assess where and when they are active. We then aimed to test which genes are negatively regulated by these miRNAs to control flowering. We show that the MIRNA157C and MIRNA157D genes have an unexpectedly important role in negatively regulating the SPL15 transcription factor and MIRNA157D is expressed in the shoot apex during floral transition. Moreover, loss of function of these MIRNA genes induced by gene editing causes early flowering. However, the genetic experiments also show that increased activity of SPL15 only explains part of the early-flowering phenotype, suggesting that MIR157CD also negatively regulate other SPL transcription factors. Similarly, we show that MIR172ABD are the major members of this family that promote flowering and that they do this partially by repressing the activity of the APETALA2 transcription factor. These results provide a clear picture of which members of these MIRNA gene families control flowering, where they are active, and of some the genes they regulate, and they form a strong basis for more detailed quantitative analyses of the regulatory network controlling flower development at the shoot apex.
Publications
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Systematic analyses of the MIR172 family members of Arabidopsis define their distinct roles in regulation of APETALA2 during floral transition. PLOS Biology, 19(2), e3001043.
Ó’Maoiléidigh, Diarmuid S.; van Driel Annabel, D.; Singh, Anamika; Sang, Qing; Le Bec, Nolwenn; Vincent, Coral; de Olalla, Enric Bertran Garcia; Vayssières, Alice; Romera, Branchat Maida; Severing, Edouard; Martinez, Gallegos Rafael & Coupland, George
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MicroRNA172 controls inflorescence meristem size through regulation of APETALA2 in Arabidopsis. New Phytologist, 235(1), 356-371.
Sang, Qing; Vayssières, Alice; Ó'Maoiléidigh, Diarmuid S.; Yang, Xia; Vincent, Coral; Bertran, Garcia de Olalla Enric; Cerise, Martina; Franzen, Rainer & Coupland, George
