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GENETICS, GENOMICS, AND MOLECULAR EVOLUTION

Identification of a Novel Chloroplast Protein AtNYE1 Regulating Chlorophyll Degradation during Leaf Senescence in Arabidopsis^{1,[C],[W],[OA]}

State Key Laboratory of Genetic Engineering, Department of Biochemistry, School of Life Sciences, Fudan University, Shanghai 200433, China

A dramatic increase of chlorophyll (Chl) degradation occurs during senescence of vegetative plant organs and fruit ripening. Although the biochemical pathway of Chl degradation has long been proposed, little is known about its regulatory mechanism. Identification of Chl degradation-disturbed mutants and subsequently isolation of responsible genes would greatly facilitate the elucidation of the regulation of Chl degradation. Here, we describe a nonyellowing mutant of Arabidopsis (Arabidopsis thaliana), nye1-1, in which 50% Chl was retained, compared to less than 10% in the wild type (Columbia-0), at the end of a 6-d dark incubation. Nevertheless, neither photosynthesis- nor senescence-associated process was significantly affected in nye1-1. Characteristically, a significant reduction in pheophorbide a oxygenase activity was detected in nye1-1. However, no detectable accumulation of either chlorophyllide a or pheophorbide a was observed. Reciprocal crossings revealed that the mutant phenotype was caused by a monogenic semidominant nuclear mutation. We have identified AtNYE1 by positional cloning. Dozens of its putative orthologs, predominantly appearing in higher plant species, were identified, some of which have been associated with Chl degradation in a few crop species. Quantitative polymerase chain reaction analysis showed that AtNYE1 was drastically induced by senescence signals. Constitutive overexpression of AtNYE1 could result in either pale-yellow true leaves or even albino seedlings. These results collectively indicate that NYE1 plays an important regulatory role in Chl degradation during senescence by modulating pheophorbide a oxygenase activity.

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: Benke Kuai (bkkuai{at}fudan.edu.cn).

^[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.107.100172

^* Corresponding author; e-mail bkkuai{at}fudan.edu.cn; fax 86–21–65642648.

Received March 25, 2007; accepted April 23, 2007; published April 27, 2007.

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