PLANT PHYSIOLOGY , Vol 105, Issue 2 643-650, Copyright © 1994 by American Society of Plant Biologists
|
DEVELOPMENT AND GROWTH REGULATION |
Retention of Photoinduction of Cytosolic Enzymes in aurea Mutant of Tomato (Lycopersicon esculentum)
K. V. Goud and R. Sharma
School of Life Sciences, University of Hyderabad, Hyderabad, 500 134 India
The tomato (Lycopersicon esculentum Mill.) aurea (au) mutant has been
characterized as a phytochrome-deficient mutant lacking spectrally
detectable phytochrome A in etiolated seedlings. Seedlings of au grown
under red light (RL) lack phytochrome regulation of nuclear genes encoding
plastidic proteins, possess ill-developed chloroplasts, and are slow to
de-etiolate. In the present study, the effect of phytochrome deficiency on
photoinduction of enzymes in etiolated au seedlings was investigated. The
photoinduction of the cytosolic enzymes amylase and nitrate reductase (NR)
and of the plastidic enzyme nitrite reductase (NiR) in au was compared with
that in the isogenic wild-type (WT) tomato and the high-pigment (hp) mutant
with exaggerated phytochrome response. In WT and hp, both brief RL pulses
and continuous RL induced amylase, NR, and NiR activities, whereas in au no
photoinduction of enzymes was observed with brief RL pulses, and continuous
RL induced only amylase and NR activities. The time courses of
photoinduction of NR and amylase in au under continuous RL followed
patterns qualitatively similar to hp and WT. A blue-light pretreatment
prior to continuous RL exposure was ineffective in inducing NiR activity in
au. Only continuous white light could elicit a photoinduction of NiR in au
seedlings. The norflurazon-triggered loss of photoinduction of NiR in WT
and hp indicated that NiR photoinduction depended on chloroplast
biogenesis. The results indicate that observed photoinduction of NR and
amylase in au may be mediated by a residual phytochrome pool.
