Abstract
The flowering time of plants is affected by modest changes in ambient temperature. However, little is known about the regulation of ambient temperature-responsive flowering by small RNAs. In this study, we show that the microRNA156 (miR156)-SQUAMOSA PROMOTER BINDING PROTEIN-LIKE3 (SPL3) module directly regulates FLOWERING LOCUS T (FT) expression in the leaf to control ambient temperature-responsive flowering. Overexpression of miR156 led to more delayed flowering at a lower ambient temperature (16°C), which was associated with down-regulation of FT and FRUITFULL expression. Among miR156 target genes, SPL3 mRNA levels were mainly reduced, probably because miR156-mediated cleavage of SPL3 mRNA was higher at 16°C. Overexpression of miR156-resistant SPL3 [SPL3(-)] caused early flowering, regardless of the ambient temperature, which was associated with up-regulation of FT and FRUITFULL expression. Reduction of miR156 activity by target mimicry led to a phenotype similar to that of SUC2::rSPL3 plants. FT up-regulation was observed after dexamethasone treatment in GVG-rSPL3 plants. Misexpression and artificial microRNA-mediated suppression of FT in the leaf dramatically altered the ambient temperature-responsive flowering of plants overexpressing miR156 and SPL3(-). Chromatin immunoprecipitation assay showed that the SPL3 protein directly binds to GTAC motifs within the FT promoter. Lesions in TERMINAL FLOWER1, SHORT VEGETATIVE PHASE, and EARLY FLOWERING3 did not alter the expression of miR156 and SPL3. Taken together, our data suggest that the interaction between the miR156-SPL3 module and FT is part of the regulatory mechanism controlling flowering time in response to ambient temperature.
Highlights
The flowering time of plants is affected by modest changes in ambient temperature
LD conditions were used because, under short-day conditions, total leaf numbers of wild-type plants grown at 23°C were almost indistinguishable from those grown at 16°C, which indicates that low ambient temperature affects the photoperiodic response (Strasser et al, 2009; Supplemental Fig. S2). 35S::MIR156b plants showed moderate late flowering at 23°C in LD conditions (25.6 leaves; Supplemental Table S1 to find detailed information on flowering time of plants used in this study; Fig. 1A)
We show that ambient temperature-responsive flowering in Arabidopsis is mediated by the miR156-SQUAMOSA PROMOTER BINDING PROTEIN-LIKE3 (SPL3)-FLOWERING LOCUS T (FT) genetic circuitry
Summary
The flowering time of plants is affected by modest changes in ambient temperature. little is known about the regulation of ambient temperature-responsive flowering by small RNAs. They commonly target mRNAs of specific transcription factors, thereby forming so-called miRNA transcription factor regulatory modules (Dugas and Bartel, 2004; Mallory and Vaucheret, 2006) Examples of such modules in the Arabidopsis (Arabidopsis thaliana) and other plant species include microRNA156 (miR156) and its targets, namely SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes. These miR156SPL regulatory modules are known to play a central role in the regulation of diverse developmental processes (Schwarz et al, 2008; Wang et al, 2008; Nodine and Bartel, 2010; Xing et al, 2010; Yu et al, 2010; Gou et al, 2011; Yang et al, 2011). Our results suggest a model in which the miR156SPL3 module directly regulates FT expression in the leaf to modulate ambient temperature-responsive flowering in Arabidopsis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
