ClpC1, an ATP-dependent Clp protease in plastids, is involved in iron homeostasis in Arabidopsis leaves.
OBJECTIVE
Iron (Fe) is necessary for plant growth and development. Although it is well known that Fe deficiency causes chlorosis in plants, it remains unclear how the Fe homeostasis is regulated in mesophyll cells. The aim of this work was to identify a gene related to Fe homeostasis in leaves.


METHODS
A spontaneous mutant irm1, which revealed typical Fe-deficiency chlorosis, was found from Arabidopsis thaliana. Using map-based cloning, the gene responsible for the altered phenotype of irm1 was cloned. The expression of genes was analysed using northern blot hybridization and multiplex RT-PCR analysis. Further, GUS staining with transgenic promoter-GUS lines and transient expression of the fusion protein with GFP were used for detecting the expression pattern of the gene in different tissues and at different developmental stages, and for the subcelluar localization of the gene product.


RESULTS
A point mutation from G to A at nucleotide 2317 of ClpC1 on chromosome V of Arabidopsis is responsible for the irm1 phenotype. The leaf chlorosis of the mutant irm1 and clpc1 (a T-DNA-inserted null mutant of ClpC1) could be converted to green by watering the soil with Fe solution. The expression intensity of ferric reductase FRO8 in irm1 and clpc1 was disordered (significantly higher than that of wild type).


CONCLUSIONS
The glycine residue at amino acid 773 of ClpC1 is essential for its functions. In addition to its known functions reported previously, ClpC1 is involved in leaf Fe homeostasis, presumably via chloroplast translocation of some nuclear-encoded proteins which function in Fe transport.
Wu
Huilan
H
The State Key Laboratory of Plant Cell and Chromosome Engineering, National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Datun Road, Chaoyang District, Beijing 100101, China.
Ji
Yanyan
Y
Du
Juan
J
Kong
Danyu
D
Liang
Hui
H
Ling
Hong-Qing
HQ
D049069:ATP-Dependent Proteases / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism*; D018087:Plastids / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation / Q000235:genetics / Q000502:physiology
D029681:Arabidopsis Proteins; D007501:Iron; D049069:ATP-Dependent Proteases
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