Isolation of a cDNA clone encoding the alternative oxidase expressed in rice anthers

Catalase and alternative oxidase cooperatively regulate programmed cell death induced by beta-glucan elicitor in potato suspension cultures

In potato (Solanum tuberosum L.) suspension cells, the expression of the gene encoding alternative oxidase (AOX) and H2O2 accumulation were induced by treatment with beta-glucan elicitor. The inhibition of catalase activity enhanced both AOX mRNA expression and the production of H2O2, whereas the ascorbate peroxidase inhibitor did not have any effect on these responses. Simultaneous inhibition of catalase and AOX activities in elicited cells dramatically increased H2O2 accumulation, leading to the disruption of mitochondrial membrane potential (deltapsi(m)) and programmed cell death (PCD). The results demonstrate, for the first time, that not only AOX but also catalase plays a central role in the suppression of mitochondrial deltapsi(m) breakdown and PCD induced by beta-glucan elicitor.

A single nucleotide polymorphism in the alternative oxidase gene among rice varieties differing in low temperature tolerance

Alternative oxidase (AOX) is encoded in a multigene family, and multiple isoforms have been observed in various plant species. We found for the first time an allelic variation in the same AOX locus. On SDS-gel blots of callus protein of rice (Oryza sativa L.), varieties without the QTL for low temperature tolerance showed a 32-kDa AOX band, whereas those with the QTL showed a 34-kDa band. The variation was attributed to the substitution of Lys(71) for Asn(71) caused by a single nucleotide polymorphism between alleles of OsAOX1a, and was tightly linked to the presence of the QTL.

AOX1c, a novel rice gene for alternative oxidase; comparison with rice AOX1a and AOX1b

A novel gene for alternative oxidase (AOX) was isolated from rice (Oryza sativa L.) and characterized. The deduced amino acid sequence of the novel AOX gene contains features that are conserved among other AOXs. This AOX gene was designated AOX1c based on a phylogenetic analysis of the AOX genes. Northern hybridization analyses revealed that AOX1c and AOX1a/AOX1b transcripts accumulated differently in various rice organs and rice seedlings under low temperature conditions. AOX1c mRNA was mainly present in young leaves under constant light, mature leaves and panicles after heading, but it was not detected in young etiolated leaves and young roots of seedlings or young panicles. On the other hand, the mRNAs of the rice AOX1a and AOX1b genes were mainly present in young roots and mature leaves. Under low temperature conditions, the steady-state mRNA levels of the rice AOX1a and AOX1b genes clearly increased with time but the rice AOX1c gene was apparently not responsive to low temperature. The rice AOX gene family and differences in their regulation are discussed.