Genetic and molecular analysis of phytochromes from the filamentous fungus Neurospora crassa.
Phytochromes (Phys) comprise a superfamily of red-/far-red-light-sensing proteins. Whereas higher-plant Phys that control numerous growth and developmental processes have been well described, the biochemical characteristics and functions of the microbial forms are largely unknown. Here, we describe analyses of the expression, regulation, and activities of two Phys in the filamentous fungus Neurospora crassa. In addition to containing the signature N-terminal domain predicted to covalently associate with a bilin chromophore, PHY-1 and PHY-2 contain C-terminal histidine kinase and response regulator motifs, implying that they function as hybrid two-component sensor kinases activated by light. A bacterially expressed N-terminal fragment of PHY-2 covalently bound either biliverdin or phycocyanobilin in vitro, with the resulting holoprotein displaying red-/far-red-light photochromic absorption spectra and a photocycle in vitro. cDNA analysis of phy-1 and phy-2 revealed two splice isoforms for each gene. The levels of the phy transcripts are not regulated by light, but the abundance of the phy-1 mRNAs is under the control of the circadian clock. Phosphorylated and unphosphorylated forms of PHY-1 were detected; both species were found exclusively in the cytoplasm, with their relative abundances unaffected by light. Strains containing deletions of phy-1 and phy-2, either singly or in tandem, were not compromised in any known photoresponses in Neurospora, leaving their function(s) unclear.
Froehlich
Allan C
AC
Department of Genetics, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Noh
Bosl
B
Vierstra
Richard D
RD
Loros
Jennifer
J
Dunlap
Jay C
JC
D017398:Alternative Splicing; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D015825:Chromosomes, Fungal; D002940:Circadian Rhythm; D003593:Cytoplasm / Q000378:metabolism; D018076:DNA, Complementary / Q000032:analysis / Q000235:genetics; D004271:DNA, Fungal; D004926:Escherichia coli / Q000235:genetics; D005091:Exons; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D008040:Genetic Linkage; D016681:Genome, Fungal; D000071677:Histidine Kinase; D007438:Introns; D007700:Kinetics; D008027:Light; D008969:Molecular Sequence Data; D009492:Neurospora crassa / Q000737:chemistry* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D016366:Open Reading Frames; D010766:Phosphorylation; D010834:Phytochrome / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D010860:Pigments, Biological / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D004271:DNA, Fungal; D005656:Fungal Proteins; D010860:Pigments, Biological; D020033:Protein Isoforms; D012333:RNA, Messenger; D010834:Phytochrome; D011494:Protein Kinases; D000071677:Histidine Kinase