01925naa a2200157 a 450000100080000000500110000800800410001910000150006024500880007526000090016352014650017270000110163770000170164870000200166577300820168516519922004-04-23       1998    bl uuuu     u00u1 u    #d1 aREILLY, K.  aOxidative stress related genes in cassava post harvest physiological deterioration.  c1998  aAbstract: Post-harvest physiological deterioration of cassava tubers has been decribed sine the 1920's and storage of the crop. During the 1970's it was demonstrated that such primary deterioration occured via endogenous processes within the root rather than via microbial deterioration. Several lines of evidence suggest that the deterioration response may be mediated by oxidative enzymes. Since initial vascular streaking develops from wound sites and vascular tissue it has been proposed that the browining reactions of deterioration result from 02 access to internal tissues followed by enzymatic oxidation of root phenolics. Candidate enzymes which have been proposed include peroxidase, catalase and polyphenol oxidase. Catalases are tetrameric heme containing enzymes which catalase the breakdown of hydrogen peroxide. A cassava cDNA clone cCATI enconding catalase (EC 1.11.1.6) has been isolated from a tuber cDNA library by hybridisation secreening with a³²P labelled cDNA probes from Nicotinia plumbaginifola. The clone represents a full length t ript and shows highest similarity to Riccinus communes cat2. The predicted protein contains a characteristic plant catalase C-terminal microbody targeting signal -SLR located 9 amino acid residues from the stop codon suggesting that the transcript may be localised in glyoxysomes within the root. Experiments underway should allow characterisation of its expression during the deterioration responce.1 aHAN, Y1 aIGLESIAS, C.1 aBEECHING, J. R.  tRevista Brasileira de Mandioca, Salvadorgv.17, p.88, nov., 1998. Suplemento.