A loss-of-function mutation in the <i>DWARF4</i>/<i>PETANKO5</i> gene enhances the late-flowering and semi-dwarf phenotypes of the <i>Arabidopsis</i> clock mutant <i>lhy-12;cca1-101</i> under continuous light without affecting <i>FLC</i> expression

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The circadian clock plays important roles in the control of photoperiodic flowering in <i>Arabidopsis</i>. Mutations in the <i>LATE ELONGATED HYPOCOTYL</i> (<i>LHY</i>) and <i>CIRCADIAN CLOCK ASSOCIATED 1</i> (<i>CCA1</i>) genes (<i>lhy;cca1</i>) accelerate flowering under short days, whereas <i>lhy;cca1</i> delays flowering under continuous light (LL). The <i>lhy;cca1</i> mutant also exhibits short hypocotyls and petioles under LL. However, the molecular mechanisms underlying the regulation of both flowering time and organ lengths in the LHY/CCA1-dependent pathway are not fully understood. To address these questions, we performed EMS mutagenesis of the <i>lhy-12;cca1-101</i> line and screened for mutations that enhance the <i>lhy;cca1</i> phenotypes under LL. In this screen, we identified a novel allele of <i>dwarf4</i> (<i>dwf4</i>) and named it <i>petanko 5</i> (<i>pta5</i>). A similar level of enhancement of the delay in flowering was observed in these two <i>dwf4</i> mutants when combined with the <i>lhy;cca1</i> mutations. The <i>lhy;cca1</i> and <i>dwf4</i> mutations did not significantly affect the expression level of the floral repressor gene <i>FLC</i> under LL. Our results suggest that a defect in brassinosteroid (BR) signaling delayed flowering independent of the <i>FLC</i> expression level, at least in plants with the <i>lhy;cca1</i> mutation grown under LL. The <i>dwf4</i>/<i>pta5</i> mutation did not enhance the late-flowering phenotype of plants overexpressing <i>SVP</i> under LL, suggesting that SVP and BR function in a common pathway that controls flowering time. Our results suggest that the <i>lhy;cca1</i> mutant exhibits delayed flowering due to both the BR signaling-dependent and -independent pathways under LL.


  • Plant Biotechnology

    Plant Biotechnology 33(4), 315-321, 2016

    Japanese Society for Plant Cell and Molecular Biology


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