Stress induces peroxisome biogenesis genes

Abstract

Peroxisomes are the cellular location of many antioxidants and are themselves significant producers of reactive oxygen species. In this report we demonstrate the induction of peroxisome biogenesis genes in both plant and animal cells by the universal stress signal molecule hydrogen peroxide. Using PEX1-LUC transgenic plants, rapid local and systemic induction of PEX1-luciferase could be demonstrated in vivo in response to physiological levels of hydrogen peroxide. PEX1-luciferase was also induced in response to wounding and to infection with an avirulent pathogen. We propose a model in which various stress situations that lead to the production of hydrogen peroxide can be ameliorated by elaboration of the peroxisome compartment to assist in restoration of the cellular redox balance.

Fig. 1. (A) AtPEX1 promoter and N-terminus of coding region. Italics show the additional 5′ sequence derived from the 215 bp partial cDNA. The two possible ATG start codons are underlined. The amino acid sequence deduced from the cDNA clone is shown below the nucleotide sequence for the first and part of the second exon. The DDWE motif where the fusion to luciferase was made is shown in bold. (B) The fusion junction between PEX1 and luciferase.

Fig. 2. Expression profile of AtPEX1 and AtPEX5 in seedlings. RNA from seedlings at the days indicated was hybridized with probes for AtPEX1, AtPEX5 and At malate synthase.

Fig. 3. H₂O₂ induces plant and animal peroxisome biogenesis genes. RNA used in (A) (northern blot) and (B) (RT–PCR) was obtained from control and 1 mM H₂O₂-treated Arabidopsis leaves, whereas in (C) (RT–PCR) the RNA is from control and 1 mM H₂O₂-treated chinese hamster ovary cells.

Fig. 4. H₂O₂ rapidly induces AtPEX1–LUC gene expression. (A) Control plants (left) were sprayed with 1 mM H₂O₂ and light emission measured after 30 min (right). Clofibrate treatment (B) and senescence (C) were used as positive controls for peroxisome proliferation.

Fig. 5. H₂O₂ induces PEX1–LUC systemically. (A) Opposite leaves (arrows) were incubated with either 1 mM H₂O₂ (bottom leaf) or 1 mM H₂O₂ plus catalase (upper leaf) for 15 min. (B) The bottom leaf was incubated with the H₂O₂-regenerating system G/GO. Light emission was measured at the indicated times.

Fig. 6. PEX1–LUC is induced by pathogen attack and wounding. (A) Pseudomonas syringae pv. tomato was inoculated (I) into the indicated leaf and the effect on PEX1–LUC expression compared with a control leaf inoculated with buffer only. Light emission was measured at the indicated times. (B–D) Wounded plants. (B) Whole plant before (left) and 90 min after wounding (right). (C) Close up of a leaf of the plant shown in (B). (D) Close up of leaf before and after wounding; different plant.