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Phytochrome B integrates light and temperature signals in Arabidopsis

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Science  18 Nov 2016:
Vol. 354, Issue 6314, pp. 897-900
DOI: 10.1126/science.aaf5656
  • Fig. 1 The status of phyB responds to light and temperature.

    (A) Three-stage model of phyB (11). Our working hypothesis is that D2 integrates light cues (via k1 and k2) and temperature cues (via kr2 and mainly kr1). (B to E) Warm temperatures reduce Pfr levels of full-length recombinant phyB exposed in vitro to 1 [(B) and (D)] or 5.1 [(C) and (E)] μmol m−2 s−1 of continuous red light. [(B) and (C)] Absorbance kinetics (maximal absorption decreased with temperature, P < 0.05). [(D) and (E)] ∆ absorbance in samples incubated in darkness or exposed to continuous red light to reach a steady state. The difference between Δ absorbance at 665 and 725 nm decreased with temperature (P < 0.01). (F) Warm temperatures reduce the levels of Pfr and D2 in vivo measured in phyA mutant seedlings overexpressing phyB (9) exposed to 1 μmol m−2 s−1 red light. Means ± SE of three biological replicates. (G) Warm temperatures increase kr1 [calculated from (F), P < 0.001].

  • Fig. 2 phyB nuclear bodies respond to light and temperature.

    (A) Dual response of phyB-YFP nuclear bodies to temperature (white light, 10 μmol m−2 s−1). Scale bar, 5 μm. (B) Estimation of D2 in the wild type by using its average phyB nuclear body size (NB) as input in the model relating NB to D2 in lines expressing stabilized phyB (phyBY361F-YFP and phyBR582A-YFP). (C) Impact of temperature on D2. Difference in log-transformed D2 averaged for 5 to 11 conditions (±SE) covering a wide range of irradiances and red/far-red ratios (temperature effect, P < 0.05).

  • Fig. 3 phyB mediates growth responses to light and temperature.

    (A to C) Observed values of hypocotyl growth (G) in white light–grown seedlings of eight genotypes exposed to 25 combinations of irradiance and temperature versus the values predicted by the growth model. The different irradiances (A), temperatures (B), and genotypes (C) are color-coded to show that the relationship between observed and predicted values is not biased for any of these factors (within the range tested here). Col, Columbia wild type; phyB, phyB null mutant; phyB, phyBY361F, and phyBR582A, transgenic lines expressing wild-type or mutated phyB in the phyB null mutant background. [(B), inset] The goodness of fit of the model (Pearson’s χ2 test) is greatly deteriorated when temperature effects on D2 are not incorporated (both versions of the model have the same number of parameters). (D) Contribution to the inhibition of growth of each one of the three temperature-dependent terms of the growth model. Topmost line is the horizontal base line of no low-temperature effects (G incorporating only light effects at 30°C). Downward, the lines indicate G calculations successively incorporating the phyB-dependent temperature effects, the phyB-temperature interaction, and the phyB-independent temperature effect. The colored areas highlight the contribution of each additional term incorporated in the calculations.

Supplementary Materials

  • Phytochrome B integrates light and temperature signals in Arabidopsis

    Martina Legris, Cornelia Klose, E. Sethe Burgie, Cecilia Costigliolo, Maximiliano Neme, Andreas Hiltbrunner, Philip A. Wigge, Eberhard Schäfer, Richard D. Vierstra, Jorge J. Casal

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods
    • Figs. S1 to S11
    • Table S1 to S4
    • References

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