Arabidopsis TERMINAL FLOWER 2 gene encodes a heterochromatin protein 1 homolog and represses both FLOWERING LOCUS T to regulate flowering time and several floral homeotic genes.
Floral transition should be strictly regulated because it is one of the most critical developmental processes in plants. Arabidopsis terminal flower 2 (tfl2) mutants show an early-flowering phenotype that is relatively insensitive to photoperiod, as well as several other pleiotropic phenotypes. We found that the early flowering of tfl2 is caused mainly by ectopic expression of the FLOWERING LOCUS T (FT) gene, a floral pathway integrator. Molecular cloning of TFL2 showed that it encodes a protein with homology to heterochromatin protein 1 (HP1) of animals and Swi6 of fission yeast. TFL2 protein localizes in subnuclear foci and expression of the TFL2 gene complemented yeast swi6(-) mutants. These results suggested that TFL2 might function as an HP1 in Arabidopsis: Gene expression analyses using DNA microarrays, however, did not show an increase in the expression of heterochromatin genes in tfl2 mutants but instead showed the upregulation of the floral homeotic genes APETALA3, PISTILLATA, AGAMOUS and SEPALLATA3. The pleiotropic phenotype of the tfl2 mutant could reflect the fact that TFL2 represses the expression of multiple genes. Our results demonstrate that despite its homology to HP1, TFL2 is involved in the repression of specific euchromatin genes and not heterochromatin genes in Arabidopsis.
Kotake
Toshihisa
T
Research Institute for Biological Sciences, Okayama, 716-1241 Japan.
Takada
Shinobu
S
Nakahigashi
Kenji
K
Ohto
Masaaki
M
Goto
Koji
K
D026342:AGAMOUS Protein, Arabidopsis / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000302:isolation & purification*; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000302:isolation & purification*; D018076:DNA, Complementary / Q000032:analysis / Q000235:genetics; D035264:Flowers / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D005801:Genes, Homeobox / Q000235:genetics; D018398:Homeodomain Proteins / Q000235:genetics; D026161:MADS Domain Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics* / Q000302:isolation & purification* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000235:genetics / Q000302:isolation & purification
D026342:AGAMOUS Protein, Arabidopsis; D029681:Arabidopsis Proteins; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone; D018076:DNA, Complementary; D018398:Homeodomain Proteins; D026161:MADS Domain Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C101342:APETALA 3 protein, Arabidopsis; C418905:FT protein, Arabidopsis; C090225:PISTILLATA protein, Arabidopsis; C121158:SEP3 protein, Arabidopsis; C075111:SWI6 protein, S cerevisiae; C477788:At5g17690 protein, Arabidopsis