Planta

, Volume 197, Issue 2, pp 213–218

Co-action between phytochrome B and HY4 in Arabidopsis thaliana

  • Jorge J. Casal
  • Herán Boccalandro
Article

DOI: 10.1007/BF00202639

Cite this article as:
Casal, J.J. & Boccalandro, H. Planta (1995) 197: 213. doi:10.1007/BF00202639

Abstract

A combination of physiological and genetic approaches was used to investigate whether phytochromes and blue light (BL) photoreceptors act in a fully independent manner during photomorphogenesis of Arabidopsis thaliana (L.) Heynh. Wild-type seedlings and phyA, phyBand hy4 mutants were daily exposed to 3 h BL terminated with either a red light (R) or a far-red light (FR) pulse. In wild-type and phyA-mutant seedlings, BL followed by an R pulse inhibited hypocotyl growth and promoted cotyledon unfolding. The effects of BL were reduced if exposure to BL was followed by an FR pulse driving phytochrome to the R-absorbing form (Pr). In the wild type, the effects of R versus FR pulses were small in seedlings not exposed to BL. Thus, maximal responses depended on the presence of both BL and the FR-absorbing form of phytochrome (Pfr) in the subsequent dark period. Impaired responses to BL and to R versus FR pulses were observed in phyB and hy4 mutants. Simultaneous irradiation with orange light indicated that BL, perceived by specific BL photoreceptors (i.e. not by phytochromes), required phytochrome B to display a full effect. These results indicate interdependent co-action between phytochrome B and BL photoreceptors, particularly the HY4 gene product. No synergism between phytochrome A (activated by continuous or pulsed FR) and BL photoreceptors was observed.

Key words

Arabidopsis (hy4 mutant) Blue-light photo-receptors Hypocotyl growth Photomorphogenic mutants Phytochrome 

Abbreviations

BL

blue light

D

darkness

FR

far-redlight

FRc

continuous FR

Pfr

FR-absorbing form of phytochrome

Pfr/P

proportion of phytochrome as Pfr

phyA

phytochrome A

phyB

phytochrome B

R

red light

WT

wild type

Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • Jorge J. Casal
    • 1
  • Herán Boccalandro
    • 1
  1. 1.Departamento de Ecología, Facultad de AgronomíaUniversidad de Buenos AiresBuenos AiresArgentina

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