A cDNA encoding a dehydrin was isolated from the flavedo of the chilling-sensitive Fortune mandarinfruit (
Citrus clementina Hort. Ex Tanaka ×
Citrus reticulata Blanco) and designed as
Crcor15. Thepredicted CrCOR15 protein is a K
2S member of a closely related dehydrin family from
Citrus, sinceit contains two tandem repeats of the unusual
Citrus K-segment and one S-segment (serine cluster)at an unusual C-terminal position.
Crcor15 mRNA is consistently and highly expressed in the flavedoduring fruit development and maturation. The relative abundance of
Crcor15 mRNA in the flavedowas estimated to be higher than 1% of total RNA. The high mRNA level remained unchanged duringfruit storage at chilling (2
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C) and nonchilling (12
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C) temperatures, and it was depressed by aconditioning treatment (3 days at 37
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C) that induced chilling tolerance. Therefore, the expression of
Crcor15 appears not to be related to the acquisition of chilling tolerance in mandarin fruits. However,
Crcor15, which was barely detected in unstressed mandarin leaves, was rapidly induced in responseto both low temperature and water stress. COR15 protein was expressed in
Escherichia coli, andthe purified protein conferred in vitro protection against freezing and dehydration inactivation. Thepotential role of
Citrus COR15 is discussed.Keywords: Citrus; dehydrin; chilling injury; freezing; late embryogenesis abundant (LEA); maturation;water stress