Abstract
Phytochromes are photoreceptors for sensing red and far-red light in plants. We isolated VOZ (Vascular plant One-Zinc finger) as a phytochrome-interacting factor by yeast-two hybrid screening. VOZ is conserved in most land plants and Arabidopsis has two VOZ genes, VOZ1 and VOZ2. We found that VOZs promote flowering and function downstream of phyB and upstream of FT. It is known that phyB functions in mesophyll cells and FT is expressed in vascular bundles, so we analyzed the expression levels of VOZ in mesophyll cells and vascular bundles. VOZ1 was expressed only in vascular bundles, but VOZ2 was expressed in vascular bundles and mesophyll cells. We also analyzed the tissue-specificity of VOZ proteins. We made two constructs, one each for VOZ1 and VOZ2, which consisted of the GUS-fused VOZ regulated by own promoter. When either of these two constructs was transformed into voz1 voz2 double mutant, the late-flowering phenotype of the mutant was complemented. We performed GUS-staining and found that VOZ1 accumulated in the vascular bundles and VOZ2 accumulated in both the vascular bundles and the mesophyll cells. These results suggest that VOZs regulate flowering in vascular bundles.
