Molecular cloning and function analysis of the stay green gene in rice

Chloroplasts undergo drastic morphological and physiological changes during senescence with a visible symptom of chlorophyll (Chl) degradation. A stay green mutant was identified and then isolated from the japonica rice (Oryza sativa) cv. Huazhiwu by γ-ray irradiation. The stay green mutant was char...

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Bibliographic Details
Published in:	The Plant journal : for cell and molecular biology Vol. 52; no. 2; pp. 197 - 209
Main Authors:	Jiang, Huawu, Li, Meiru, Liang, Naiting, Yan, Hongbo, Wei, Yubo, Xu, Xinlan, Liu, Jian, Xu, Zhifang, Chen, Fan, Wu, Guojiang
Format:	Journal Article
Language:	English
Published:	Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01-10-2007 Blackwell Publishing Ltd Blackwell Science
Subjects:	Alleles Amino Acid Sequence Biological and medical sciences Botany Chl breakdown Chlorophyll - metabolism Chloroplasts - ultrastructure Cloning Cloning, Molecular Fundamental and applied biological sciences. Psychology Gene Expression Regulation, Plant Genes, Plant - genetics Genes. Genome Molecular and cellular biology Molecular biology Molecular genetics Molecular Sequence Data Mutation Oryza - genetics Oryza - metabolism Oryza sativa Oryza sativa L Phylogeny Plant Leaves Plant Proteins - genetics Plant Proteins - metabolism Rice senescence stay green thylakoid Chlorophyll Monocotyledones Senescence Oryza sativa L Plant leaf Thylakoid Cytokinin Chl breakdown Oryza sativa Gene Gramineae Angiospermae Spermatophyta Mutation Photosynthesis stay green Chloroplast
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Summary:	Chloroplasts undergo drastic morphological and physiological changes during senescence with a visible symptom of chlorophyll (Chl) degradation. A stay green mutant was identified and then isolated from the japonica rice (Oryza sativa) cv. Huazhiwu by γ-ray irradiation. The stay green mutant was characterized by Chl retention, stable Chl-protein complexes, and stable thylakoid membrane structures, but lost its photosynthetic competence during senescence. The gene, designated Stay Green Rice (SGR), was cloned by a positional cloning strategy encoding an ancient protein containing a putative chloroplast transit peptide. SGR protein was found in both soluble and thylakoid membranes in rice. SGR, like the gene for pheophorbide a oxygenase (PaO), was constitutively expressed, but was upregulated by dark-induced senescence in rice leaves. Senescence-induced expression of SGR and PaO was enhanced by ABA, but inhibited by cytokinin. Overexpression of SGR reduced the number of lamellae in the grana thylakoids and reduced the Chl content of normally growing leaves. This indicates that upregulation of SGR increases Chl breakdown during senescence in rice. A small quantity of chlorophyllide a accumulated in sgr leaves, but this also accumulated in wild-type rice leaves during senescence. Some pheophorbide a was detected in sgr leaves in the dark. According to these observations, we propose that SGR may be involved in regulating or taking part in the activity of PaO, and then may influence Chl breakdown and degradation of pigment-protein complex.
Bibliography:	http://dx.doi.org/10.1111/j.1365-313X.2007.03221.x ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0960-7412 1365-313X
DOI:	10.1111/j.1365-313x.2007.03221.x