Molecular cloning and tissue-specific expression of an anionic peroxidase in zucchini.
A calcium-pectate-binding anionic isoperoxidase (APRX) from zucchini (Cucurbita pepo) was purified and subjected to N-terminal amino acid microsequencing. The cDNA encoding this enzyme was obtained by reverse transcriptase polymerase chain reaction from a cDNA library. It encoded a mature protein of 309 amino acids exhibiting all of the sequence characteristics of a plant peroxidase. Despite the presence of a C-terminal propeptide, APRX was found in the apoplast. APRX protein and mRNA were found in the root, hypocotyls, and cotyledons. In situ hybridization showed that the APRX-encoding gene was expressed in many different tissues. The strongest expression was observed in root epidermis and in some cells of the stele, in differentiating tracheary elements of hypocotyl, in the lower and upper epidermis, in the palisade parenchyma of cotyledons, and in lateral and adventitious root primordia. In the hypocotyl hook there was an asymmetric expression, with the inner part containing more transcripts than the outer part. Treatment with 2,3,5-triiodobenzoic acid reduced the expression of the APRX-encoding gene in the lower part of the hypocotyl. Our observations suggest that APRX could be involved in lignin formation and that the transcription of its gene was related to auxin level.
Laboratoire de Biochimie et Physiologie Végétales, Université de Genève, Place de l'Université 3, CH-1211 Geneva, Switzerland.
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Carpin
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Crèvecoeur
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Greppin
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Penel
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D019662:Cucurbitaceae / Q000201:enzymology* / Q000235:genetics; D018076:DNA, Complementary; D018744:DNA, Plant; D015870:Gene Expression; D008969:Molecular Sequence Data; D010544:Peroxidases / Q000235:genetics* / Q000302:isolation & purification; D018517:Plant Roots / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D018749:RNA, Plant / Q000096:biosynthesis
D018076:DNA, Complementary; D018744:DNA, Plant; D012333:RNA, Messenger; D018749:RNA, Plant; D010544:Peroxidases; C120494:anionic peroxidase