High-and low-intensity photosystems in Phycomyces phototropism: Effects of mutations in genes madA, madB, and madC

A. Palit, P. Galland, E. D. Lipson

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

Sporangiophores of Phycomyces blakesleeanus Burgeff that have been grown in darkness and are then suddenly exposed to unilateral light show a two-step bending response rather than a smooth, monotonic response found in light-adapted specimens (Galland and Lipson, 1987, Proc. Natl. Acad. Sci. USA 84, 104-108). The stepwise bending is controlled by two photosystems optimized for the low-and high-intensity ranges. These two photosystems have now been studied in phototropism mutants with defects in genes madA, madB, and madC. All three mutations raise the threshold of the low-intensity (low-fluence) photosystem by about 106-fold and that of the high-intensity (high-fluence) system by about 103-fold. Estimates for the light-adaptation time constants of the low-and high-intensity photosystems show that the mutants are affected in adaptation. In the mutants, the light-adaptation kinetics are only slightly affected in the low-intensity photosystem but, for the high-intensity photosystem, the kinetics are considerably slower than in the wild type.

Original languageEnglish (US)
Pages (from-to)547-553
Number of pages7
JournalPlanta
Volume177
Issue number4
DOIs
StatePublished - Apr 1 1989

Keywords

  • Mutant, behavioral (Phycomyces)
  • Photoreceptor (phototropism)
  • Phototropism (Phycomyces)
  • Phycomyces

ASJC Scopus subject areas

  • Genetics
  • Plant Science

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