No description available.

Flax (Linum usitatissimum L.) peroxidase cDNAs (FLXPER1--4) were isolated from a lambdagt10 shoot library using probes encoding the amino termini of class III plant peroxidases. These probes were obtained by PCR amplification of the library with lambda primers flanking the EcoRI cloning site, and a mixed oligonucleotide corresponding to the catalytic domain (HFHDCFV) found in secretory plant peroxidases. The transcriptional expressions of FLXPER1 and FLXPER2 appear to be specific to stem based on northern blot analyses. FLXPER1 and FLXPER2 encode acidic peroxidases of calculated isoelectric points (pIc) 4.6 and 4.7, respectively. However, FLXPER1 differs from FLXPER2 in amino acid sequence and in the possession of additional amino acids at its carboxy terminus containing motifs found in membrane-anchored proteins. The FLXPER1 anchoring motifs show striking similarity to those found in a blue copper-type protein (LP18) whose expression in pea (Pisum sativum) has been correlated with lignin deposition. FLXPER3 is expressed in leaf, root, and stein. Partial genomic sequences of FLXPER3 and a highly homologous FLXPER5 were also obtained. FLXPER3 and FLXPER5 do not have the typical class HI plant peroxidase third intron, located within the highly conserved VALSGAHT haem-binding motif. FLXPER3 and FLXPER5 do have, however, an intron downstream of this motif at a location not found in any other class III plant peroxidase gene. FLXPER4 encodes a basic (pIc 8.5) extracellular peroxidase. A modified version of the restriction fragment length polymorphism-coupled domain-directed differential display (RC4D) technique was used to evaluate class III peroxidase transcriptional expression in flax organs. The method revealed the expression of 20 to 30 peroxidase genes in each plant organ examined. It also confirmed the stem-specific nature of FLXPER2 and the ubiquitous character of FLXPER3. FLXPER1 was found in all organs investigated in contrast to results observed by northern b

The corresponding isoperoxidases from the flax genotrophs L and S have different molecular weights. Since further structural analysis will rely on knowledge of the primary structures of these molecules, the isolation of a molecular clone of this enzyme was attempted. Probing a cDNA library with a synthetic oligonucleotide was not successful, but a partial cDNA sequence was isolated by probing an S genotroph stem $ lambda$gt11 library with polyclonal antibodies raised against anionic plant peroxidases. Its longest reading frame sequence is divergent from those of other peroxidases, but contains some related segments. Genomic Southern analysis of the clone is presented, along with a study of the expression of its corresponding mRNA in plant tissues. A study on the effects of IAA, ABA and kinetin levels on the expression of peroxidase and of the putative peroxidase cloned mRNA is also presented.

No description available.