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Accueil du site > Equipes de recherche > Peroxydases : évolution et expression > Thèmes de recherche > Looking for the ancestral peroxidase in the green lineage

Looking for the ancestral peroxidase in the green lineage

Contacts : mail to Christophe DUNAND and mail to Catherine MATHÉ

Peroxidases are enzymes that catalyze reactions in which hydrogen peroxide is reduced and a variable substrate is oxidized. These proteins are present in all kingdoms and generally form gene families of varying sizes (from 2 to 138 isoforms). In plants, they have fundamental roles in various physiological processes such as detoxification of excess reactive oxygen species, defense against pathogens or the formation of cell wall (Passardi et al. ; Cosio et al. 2009). Superfamily of non-animal peroxidases is widely represented in Viridiplantae. This superfamily contains three classes (classes I, II and III) with similar tertiary structures and probably shares a common ancestral sequence. Peroxidases of class I and III are found in plants. Class I peroxidases are found in all organisms containing chloroplasts, while Class III peroxidases are specific to plants and absent from Chlamydomonas. Class III as class I show a high rate of duplications in plants.
The high rate of duplication and the emergence of a particular class can be easily correlated with the emergence of terrestrial plants, with increasing oxygen level, number of pathogens and also with the structural complexity of plants. Branches such as evolutionary Charaphyceae, intermediate between Chlamydomonas and moss are interesting. Preliminary results have detected peroxidase activity of class III from Chara zeylanica. The presence of sequence (s) coding for these proteins is highly likely but unfortunately no data are available yet. The research and the specific sequencing of Class III sequence(s) of a organism from this branch industry would certainly provide answers about the evolution of non-animal peroxidases in Viridiplantae.

The project aims to (i) to choose a candidate at the base of the green strain (Charaphyceae : Nitella hyalina, Coleochaete orbicularis , Chaetospheridium globosum, Spirogyra pratensis, Penium marg, Chlorokybus atmophyticus and Klebsormidium flaccidum available from C. Delwiche’s lab web site and prepare a BAC library (screening with specific probes and sequencing of candidate) in collaboration with the CNRGV and (ii) perform a global evolutionary analysis of the non-animal peroxidases superfamily