Expansins in deepwater rice internodes.
Cell walls of deepwater rice (Oryza sativa L.) internodes undergo long-term extension (creep) when placed under tension in acidic buffers. This is indicative of the action of the cell wall-loosening protein expansin. Wall extension had a pH optimum of around 4.0 and was abolished by boiling. Acid-induced extension of boiled cell walls could be reconstituted by addition of salt-extracted rice or cucumber cell wall proteins. Cucumber expansin antibody recognized a single protein band of 24.5-kD apparent molecular mass on immunoblots of rice cell wall proteins. Expansins were partially purified by concanavalin A affinity chromatography and sulfopropyl (SP) cation-exchange chromatography. The latter yielded two peaks with extension activity (SP20 and SP29), and immunoblot analysis showed that both of these active fractions contained expansin of 24.5-kD molecular mass. The N-terminal amino acid sequence of SP20 expansin is identical to that deduced from the rice expansin cDNA Os-EXP1. The N-terminal amino acid sequence of SP29 expansin matches that deduced from the rice expansin cDNA Os-EXP2 in six of eight amino acids. Our results show that two expansins occur in the cell walls of rice internodes and that they may mediate acid-induced wall extension.
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Michigan State University-Department of Energy Plant Research Laboratory, East Lansing 48824-1312, USA.
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D000064:Acclimatization; D000595:Amino Acid Sequence; D002021:Buffers; D002473:Cell Wall / Q000502:physiology; D002846:Chromatography, Affinity; D002852:Chromatography, Ion Exchange; D003208:Concanavalin A; D018553:Cucumis sativus; D004591:Electrophoresis, Polyacrylamide Gel; D005618:Fresh Water; D006863:Hydrogen-Ion Concentration; D015151:Immunoblotting; D008969:Molecular Sequence Data; D012275:Oryza / Q000502:physiology*; D037121:Plant Lectins; D010940:Plant Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid
D002021:Buffers; D037121:Plant Lectins; D010940:Plant Proteins; C095825:expansin protein, plant; D003208:Concanavalin A