A comparative analysis of basic helix-loop-helix proteins, AtPTF1 and NtWIN4, with reference to plastid localization
Basic helix-loop-helix (bHLH) proteins constitute one of the most abundant types of transcription factor in both plants and animals. They are considered to be localized in the nucleus, but recent surveys have revealed two exceptions, NtWIN4 from tobacco and AtPTF1 from Arabidopsis, both reported to localize to plastids. Their specific subcellular localization was suggested to be the result of structural change, whose analysis might provide clues to understanding protein evolution. Consequently we performed comparative analyses on localization features of both NtWIN4 and AtPTF1 using GFP-tagged fusion proteins. While epifluorescence from NtWIN4-GFP was clearly observed in plastids, that from AtPTF1-GFP was unexpectedly seen only in nuclei. Subsequent transcription assays using a dual-luciferase system indicated that AtPTF1 possesses clear nuclear transcriptional repression activity. It is concluded that, in contrast to the previous paradigm, AtPTF1 is a nuclear transcriptional repressor, and therefore that NtWIN4 is the only non-nucleus resident bHLH protein.
- Plant biotechnology
Plant biotechnology 24(3), 335-338, 2007-06-01
Japanese Society for Plant Cell and Molecular Biology