Base-pair opening dynamics of the microRNA precursor pri-miR156a affect temperature-responsive flowering in Arabidopsis.
Internal and environmental cues, including ambient temperature changes, regulate the timing of flowering in plants. Arabidopsis miR156 represses flowering and plays an important role in the regulation of temperature-responsive flowering. However, the molecular basis of miR156 processing at lower temperatures remains largely unknown. Here, we performed nuclear magnetic resonance studies to investigate the base-pair opening dynamics of model RNAs at 16 °C and investigated the in vivo effects of the mutant RNAs on temperature-responsive flowering. The A9C and A10CG mutations in the B5 bulge of the lower stem of pri-miR156a stabilized the C15∙G98 and U16∙A97 base-pairs at the cleavage site of pri-miR156a at 16 °C. Consistent with this, production of mature miR156 was severely affected in plants overexpressing the A9C and A10CG constructs and these plants exhibited almost no delay in flowering at 16 °C. The A10G and A9AC mutations did not strongly affect C15∙G98 and U16∙A97 base-pairs at 16 °C, and plants overexpressing A10G and A9AC mutants of miR156 produced more mature miR156 than plants overexpressing the A9C and A10CG mutants and showed a strong delay in flowering at 16 °C. Interestingly, the A9AC mutation had distinct effects on the opening dynamics of the C15∙G98 and U16∙A97 base-pairs between 16 °C and 23 °C, and plants expressing the A9AC mutant miR156 showed only a moderate delay in flowering at 16 °C. Based on these results, we propose that fine-tuning of the base-pair stability at the cleavage site is essential for efficient processing of pri-miR156a at a low temperature and for reduced flowering sensitivity to ambient temperature changes.
Department of Chemistry and RINS, Gyeongsang National University, Gyeongnam 52828, South Korea.
Hee-Eun
HE
Kim
Creative Research Initiatives, Department of Life Sciences, Korea University, Seoul 02841, South Korea.
Wanhui
W
Kim
Department of Chemistry and RINS, Gyeongsang National University, Gyeongnam 52828, South Korea.
Ae-Ree
AR
Lee
Creative Research Initiatives, Department of Life Sciences, Korea University, Seoul 02841, South Korea.
Suhyun
S
Jin
Creative Research Initiatives, Department of Life Sciences, Korea University, Seoul 02841, South Korea.
A Rim
AR
Jun
Advanced Analysis Center, Korea Institute of Science and Technology, Seoul 02792, South Korea.
Nak-Kyoon
NK
Kim
Department of Chemistry and RINS, Gyeongsang National University, Gyeongnam 52828, South Korea. Electronic address: joonhwa@gnu.ac.kr.
Joon-Hwa
JH
Lee
Creative Research Initiatives, Department of Life Sciences, Korea University, Seoul 02841, South Korea. Electronic address: jahn@korea.ac.kr.
Ji Hoon
JH
Ahn
D000222:Adaptation, Physiological / Q000235:genetics*; D017360:Arabidopsis / Q000235:genetics*; D020137:Base Pair Mismatch / Q000235:genetics*; D020029:Base Pairing / Q000235:genetics*; D001483:Base Sequence; D035264:Flowers / Q000235:genetics*; D035683:MicroRNAs / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D013696:Temperature; D013697:Thermosensing / Q000235:genetics*
D035683:MicroRNAs; C559759:Mirn156 microRNA, Arabidopsis
Base-pair opening dynamics; Flowering; Microrna biogenesis; NMR; RNA