Identification by large-scale screening of phytochrome-regulated genes in etiolated seedlings of Arabidopsis using a fluorescent differential display technique.

Phytochrome A (PhyA)-regulated genes in 6-d-old etiolated seedlings of Arabidopsis Landsberg erecta were identified by fluorescent differential display. To screen for PhyA-regulated genes, mRNA fingerprints of the wild type and the phyA-201 mutant were compared from samples prepared 4 h after far-red light irradiation. Approximately 30,000 bands of cDNA were displayed by fluorescent differential display, and 24 differentially expressed bands were observed. Sequence analysis revealed that they represent 20 distinct genes. Among them, 15 genes were confirmed as PhyA regulated by northern-blot (or reverse transcription-polymerase chain reaction) analysis. Thirteen up-regulated genes included 12 known genes that encode nine photosynthetic proteins, two enzymes involved in the biosynthesis of chlorophyll, one DNA damage repair/toleration-related protein, and one unknown gene. Two down-regulated genes were identified as encoding a xyloglucan endotransglycosylase-related protein and a novel member of the ASK protein kinase family. In the phyA-201 mutant and the phyA-201phyB-1 double mutant, expression of all of these genes was photoreversibly up- or down-regulated by type II phytochromes. The results indicate that modes of photoperception differ between PhyA and PhyB, but that both types of phytochromes have overlapping effects on the photoregulation of gene expression.