title: Isolation, chromosomal localization, and differential expression of mitochondrial manganese superoxide dismutase and chloroplastic copper/zinc superoxide dismutase genes in wheat.
abstract: Superoxide dismutase (SOD) gene expression was investigated to elucidate its role in drought and freezing tolerance in spring and winter wheat (Triticum aestivum). cDNAs encoding chloroplastic Cu/ZnSODs and mitochondrial MnSODs were isolated from wheat. MnSOD and Cu/ZnSOD genes were mapped to the long arms of the homologous group-2 and -7 chromosomes, respectively. Northern blots indicated that MnSOD genes were drought inducible and decreased after rehydration. In contrast, Cu/ZnSOD mRNA was not drought inducible but increased after rehydration. In both spring and winter wheat seedlings exposed to 2 degrees C, MnSOD transcripts attained maximum levels between 7 and 49 d. Transcripts of Cu/ZnSOD mRNA were detected sooner in winter than in spring wheat; however, they disappeared after 21 d of acclimation. Transcripts of both classes of SOD genes increased during natural acclimation in both spring and winter types. Exposure of fully hardened plants to three nonlethal freeze-thaw cycles resulted in Cu/Zn mRNA accumulation; however, MnSOD mRNA levels declined in spring wheat but remained unchanged in winter wheat. The results of the dehydration and freeze-thaw-cycle experiments suggest that winter wheat has evolved a more effective stress-repair mechanism than spring wheat.
authors.affiliation: Crop Development Centre, University of Saskatchewan, 51 Campus Drive, Saskatoon, Saskatchewan, Canada S7N 5A8.
authors.forename: G
authors.initials: G
authors.lastname: Wu
authors.forename: R W
authors.initials: RW
authors.lastname: Wilen
authors.forename: A J
authors.initials: AJ
authors.lastname: Robertson
authors.forename: L V
authors.initials: LV
authors.lastname: Gusta
mesh_terms: D002736:Chloroplasts / Q000235:genetics; D002874:Chromosome Mapping; D018744:DNA, Plant / Q000235:genetics; D015870:Gene Expression; D017343:Genes, Plant; D008928:Mitochondria / Q000201:enzymology; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics* / Q000302:isolation & purification*; D014908:Triticum / Q000201:enzymology* / Q000235:genetics*
chemical_list: D018744:DNA, Plant; D012333:RNA, Messenger; D018749:RNA, Plant; D013482:Superoxide Dismutase