Detection and localization of a chloroplast-encoded HU-like protein that organizes chloroplast nucleoids

Tamaki Kobayashi, Manabu Takahara, Shin Ya Miyagishima, Haruko Kuroiwa, Narie Sasaki, Niji Ohta, Motomichi Matsuzaki, Tsuneyoshi Kuroiwa

Research output: Contribution to journalArticlepeer-review

61 Scopus citations


Chloroplast DNA (cpDNA) is packed into discrete structures called chloroplast nucleoids (cp-nucleoids). The structure of cpDNA is thought to be important for its maintenance and regulation. In bacteria and mitochondria, histone-like proteins (such as HU and Abf2, respectively) are abundant and play important roles in DNA organization. However, a primary structural protein has yet to be found in cp-nucleoids. Here, we identified an abundant DNA binding protein from isolated cp-nucleoids of the primitive red alga Cyanidioschyzon merolae. The purified protein had sequence homology with the bacterial histone-like protein HU, and it complemented HU-lacking Escherichia coli mutants. The protein, called HC (histone-like protein of chloroplast), was encoded by a single gene (CmhupA) in the C. merolae chloroplast genome. Using immunofluorescence and immunoelectron microscopy, we demonstrated that HC was distributed uniformly throughout the entire cp-nucleoid. The protein was expressed constitutively throughout the cell and the chloroplast division cycle, and it was able to condense DNA. These results indicate that HC, a bacteria-derived histone-like protein, primarily organizes cpDNA into the nucleoid.

Original languageEnglish (US)
Pages (from-to)1579-1589
Number of pages11
JournalPlant Cell
Issue number7
StatePublished - 2002
Externally publishedYes

ASJC Scopus subject areas

  • Plant Science
  • Cell Biology


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