Figure 1.

The Y²⁷⁶H Mutant of Phytochrome B Is Functionally Active in Vivo.

(A) Five-week-old transgenic Ler plants expressing PHYB wild-type (B) and PHYB^Y276H (B^Y276H) mutant cDNA constructs grown under continuous W at a fluence rate of 50 μmol m⁻² s⁻¹ are hypersensitive to light.

(B) PHYB^Y276H expression rescues the phenotype of the phyB-5 (phyB) null mutant under the same conditions as (A). Ler wild-type, untransformed phyB-5, and phyB-5 mutant transformed with the wild-type PHYB cDNA construct (B) or the PHYB-GFP chimera cDNA (B-GFP) (Yamaguchi et al., 1999) are shown for comparative purposes.

(C) Six-day-old seedlings expressing cDNA and genomic constructs of wild-type PHYB (B) or the PHYB^Y276H mutant were grown under 20 μmol m⁻² s⁻¹ continuous R. One representative line from transformation of Ler wild-type (i.e., B#1 and B^Y276H#3 cDNAs), phyB-5 (i.e., B#7 and B^Y276H#10 cDNAs), and phyA-201/phyB-5 (i.e., B#2 and B^Y276H#3 cDNAs; and B#14 and B^Y276H#5 genes) is shown, along with R-grown untransformed parent and PHYB-GFP/phyB plant lines.

(D) Immunoblot analysis of PHYB protein level in wild-type, phyB, phyA, phyA phyB mutants, and PHYB^Y276H-expressing transgenic plants using monoclonal anti-PHYB antibodies. Total protein extracts (40 μg) from 6-d-old dark-grown seedlings were loaded on each lane. Tubulin was used as loading control.