title: Ozone and aging up-regulate type II metacaspase gene expression and global metacaspase activity in the leaves of field-grown maize (Zea mays L.) plants.
abstract: Maize plants (Zea mays L. cv. NK Perform) were exposed to O(3)-enriched air, using a new field fumigation system. Transcriptional changes for three type II-metacaspase genes were studied in the leaves (ranks 10 and 12), using quantitative real-time PCR. Global metacaspase activity was measured using metacaspase-specific synthetic tripeptide Boc-GRR-AMC. Aging had little effect on mRNA accumulation whereas four to six-fold increases were observed for the most O(3)-responsive type II metacaspase genes, in the older leaves 10. Global metacaspase activity increased by 257% and 333% in leaves 12 and 10, respectively, in response to the highest cumulated concentration. In non-fumigated plants, metacaspase activity progressively increased over the course of the experiment and always was higher in the older leaves 10. Together, these results suggest that metacaspase-mediated proteolysis is a crucial step in leaf responses to both O(3) and age-mediated senescence.
authors.affiliation: Equipe IBIOS, UMR 7618 Bioemco, Université Paris Est-Créteil, 61 Avenue du Général de Gaulle, 94010 Créteil Cedex, France.
authors.forename: Rafiq
authors.initials: R
authors.lastname: Ahmad
authors.forename: Yasmine
authors.initials: Y
authors.lastname: Zuily-Fodil
authors.forename: Chantal
authors.initials: C
authors.lastname: Passaquet
authors.forename: Olivier
authors.initials: O
authors.lastname: Bethenod
authors.forename: Romain
authors.initials: R
authors.lastname: Roche
authors.forename: Anne
authors.initials: A
authors.lastname: Repellin
mesh_terms: D000393:Air Pollutants / Q000633:toxicity*; D020169:Caspases / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D010126:Ozone / Q000633:toxicity*; D018515:Plant Leaves / Q000378:metabolism*; D015854:Up-Regulation; D003313:Zea mays / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism
chemical_list: D000393:Air Pollutants; D010126:Ozone; D020169:Caspases