Effects of gibberellins on seed germination of phytochrome-deficient mutants of Arabidopsis thaliana.
Experiments were carried out to explore the involvement of gibberellins (GAs) in the light-induced germination of Arabidopsis thaliana (L.) Heynh, using wild type (WT) and phytochrome-deficient mutants (phyA, phyB and phyAphyB deficient in phytochrome A, B and A plus B, respectively). Seed germination of WT and phytochrome-deficient mutants was inhibited by uniconazole (an inhibitor of an early step in biosynthesis of GA, the oxidation of ent-kaurene) and prohexadione (an inhibitor of late steps, namely, 2 beta- and 3 beta-hydroxylation). This inhibition was overcome by simultaneous application of 10(-5) M GA4. The relative activity of GAs for promoting germination of uniconazole-treated seeds was GA4 > GA1 = GA9 > GA20. The wild type and the phyA and phyB mutants had an increased response to a red light pulse in the presence of GA1, GA4, GA9, GA20 and GA24 but there were no significant differences in activity of each GA between the mutants. Therefore, neither phytochrome A nor hytochrome B appears to regulate GA biosynthesis from GA12 to GA4 during seed germination, since the conversion of GA12 to GA9 is regulated by one enzyme (GA 20-oxidase). However, GA responsiveness appears to be regulated by phytochromes other than phytochromes A and B, since the phyAphyB double mutant retains the photoreversible increased response to GAs after a red light pulse.
Yang
Y Y
YY
Laboratory for Plant Hormone Function, Institute of Physical and Chemical Research (RIKEN), Saitama, Japan.
Nagatani
A
A
Zhao
Y J
YJ
Kang
B J
BJ
Kendrick
R E
RE
Kamiya
Y
Y
D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000528:radiation effects; D029681:Arabidopsis Proteins; D018525:Germination / Q000502:physiology*; D005875:Gibberellins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D008027:Light; D009154:Mutation; D010786:Photoreceptor Cells; D010834:Phytochrome / Q000235:genetics*; D051942:Phytochrome A; D051939:Phytochrome B; D012639:Seeds; D014157:Transcription Factors; D014230:Triazoles / Q000494:pharmacology
D029681:Arabidopsis Proteins; D005875:Gibberellins; C497973:PHYA protein, Arabidopsis; C497952:PHYB protein, Arabidopsis; D051942:Phytochrome A; D014157:Transcription Factors; D014230:Triazoles; D010834:Phytochrome; D051939:Phytochrome B; C092705:uniconazole