miR172 signals are incorporated into the miR156 signaling pathway at the SPL3/4/5 genes in Arabidopsis developmental transitions
In plants, developmental timing is coordinately regulated by a complex signaling network that integrates diverse intrinsic and extrinsic signals. miR172 promotes photoperiodic flowering. It also regulates adult development along with miR156, although the molecular mechanisms underlying this regulation are not fully understood. Here, we demonstrate that miR172 modulates the developmental transitions by regulating the expression of a subset of the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes, which are also regulated by miR156. The SPL3/4/5 genes were upregulated in the miR172-overproducing plants (35S:172) and its target gene mutants that exhibit early flowering. In contrast, expression of other SPL genes was not altered to a discernible level. Kinetic measurements of miR172 abundance in the transgenic plants expressing the MIR156a gene driven by a β-estradiol-inducible promoter revealed that expressions of miR172 and miR156 are not directly interrelated. Instead, the 2 miRNA signals are integrated at the SPL3/4/5 genes. Notably, analysis of developmental patterns in the 156 × 172 plants overproducing both miR172 and miR156 showed that whereas vegetative phase change was delayed as observed in the miR156-overproducing plants (35S:156), flowering initiation was accelerated as observed in the 35S:172 transgenic plants. Together, these observations indicate that although miR172 and miR156 play distinct roles in the timing of developmental phase transitions, there is a signaling crosstalk mediated by the SPL3/4/5 genes.
KeywordsDevelopmental timing Flowering initiation miR156 miR172 SPL3/4/5
FLOWERING LOCUS T
Quantitative real-time RT-PCR
SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1
SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 3/4/5
TARGET OF EAT 1/2
We thank Narry Kim for scientific discussions and Emily Wheeler for editorial assistance. This work was supported by the Brain Korea 21 and Biogreen 21 (20080401034001) Programs and by grants from the Plant Signaling Network Research Center, the National Research Foundation of Korea (20100014373 and 2009-0087317), and from the Agricultural R & D Promotion Center (309017-5), Korea Ministry for Food, Agriculture, Forestry and Fisheries.
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