MOLECULAR-CLONING AND CHARACTERIZATION OF PEROXIDASES FROM BUFFEL GRASS (CENCHRUS-CILIARIS L)

Buffel grass (Cenchrus ciliaris L.) peroxidase cDNAs were isolated by hybridisation to an oligonucleotide from a conserved region of all pla nt peroxidases and a peroxidase cDNA clone from wheat, The 36 clones i solated were classified into one homogenous and three apparently heter ogenous groups by cross-hybridisation and sequence homologies. Nine cD NAs were subcloned, partially sequenced and identified as peroxidase h omologues by the presence of conserved sequences. Two full-length clon es (PX7 and PX18) were completely sequenced and the deduced protein se quences revealed between 38% and 77% homology to other plant peroxidas es. The mRNAs corresponding to five peroxidase cDNAs were analysed by northern analysis, to test for tissue specific or wound inducible expr ession. The peroxidases encoded by three clones, including PX7 and PX1 8, were expressed preferentially in leaves. The other two clones showe d a marked wound response in leaves. No clone was strongly expressed i n stems. Southern blot analysis indicated that PX18 is coded for by a single copy gene, whereas PX7 is represented in the buffel grass genom e by five or six copies. This indicates the complexity of the buffel g rass peroxidase gene family with respect to identification of peroxida se genes implicated in defence or developmental lignification.