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CELL BIOLOGY AND SIGNAL TRANSDUCTION

White Leaf Sectors in yellow variegated2 Are Formed by Viable Cells with Undifferentiated Plastids^{1,[C],[W],[OA]}

Research Institute for Bioresources, Okayama University, Kurashiki, Okayama 710–0046, Japan

The yellow variegated2 (var2) is one of the best-characterized Arabidopsis (Arabidopsis thaliana) mutants showing leaf variegation. Leaf variegation of var2 results from the loss of an ATP-dependent metalloprotease, FtsH2, which is a major component of the FtsH heterocomplex in thylakoid membranes. While the functional role of FtsH2 in protein quality control has been extensively studied, the physiological state of plastids in white tissues of the var2 is not well characterized. Here we show that the white tissue in var2 is neither the result of photobleaching nor enhanced senescence. Visualization of plastids by plastid-targeted green fluorescent protein revealed that plastids in the white sector are distinct and have undifferentiated characteristics. The plastids are also distinct in that they contain large nucleoids, a complex structure of plastid DNA and proteins, that are typically found in undifferentiated plastids. Comparative analyses of protein profiles from green and white tissues suggested that the difference was observed in the proteins related to photosynthesis but not due to proteins of other organelles. Thus, cells in the white tissue are viable and their defect is limited to plastid function. The plastid accumulates normal levels of chloroplast transcripts, whereas a substantial repression of nuclear-encoded photosynthetic genes was evident in the white sector. Based upon these results, we inferred that the white sectors in var2 are made by viable cells that have plastids arrested in thylakoid formation. A proposed model to form the variegated sector in var2 is provided.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Wataru Sakamoto (saka{at}rib.okayama-u.ac.jp).

^[C] Some figures in this article are displayed in color online but in black and white in the print edition.

^[W] The online version of this article contains Web-only data.

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www.plantphysiol.org/cgi/doi/10.1104/pp.107.099002

^* Corresponding author; e-mail saka{at}rib.okayama-u.ac.jp; fax 81–86–434–1206.

Received March 7, 2007; accepted April 10, 2007; published April 20, 2007.

This article has been cited by other articles:

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