title: A mutant of the Arabidopsis thaliana LIPOXYGENASE1 gene shows altered signalling and oxidative stress related responses after cadmium exposure.
abstract: Lipoxygenases (LOXes, EC 1.13.11.12) are involved in growth, development and responses to stress. Earlier results suggested a role in stress generation, signalling and/or responses when Arabidopsis thaliana is exposed to cadmium (Cd), and expression of the cytosolic LOX1 was highly upregulated in the roots after Cd exposure. To investigate the involvement of LOX1 in early metal stress responses, three-week-old wild-type and lox1-1 mutant A. thaliana plants were acutely (24 h) exposed to realistic Cd concentrations (5 and 10 μM) and several oxidative stress and signalling related parameters were studied at transcriptional and biochemical levels. Transcription of several genes encoding ROS producing and scavenging enzymes failed to be induced up to wild-type levels after Cd exposure. Expression of 9-LOX enzymes was inhibited in lox1-1 mutant roots due to lack of functional LOX1 and downregulated LOX5 expression, and the lox1-1 mutation also interfered with the expression of genes involved in jasmonate biosynthesis. LOX1 and RBOHD may be involved in stress signalling from roots to shoots, as the induction of APX2 expression, which is dependent on RBOHD activity, was disrupted in lox1-1 while RBOHD failed to be upregulated. A different pattern of H(2)O(2) production and ascorbate and glutathione levels in lox1-1 mutants after Cd exposure may have indirectly influenced gene expression patterns. Although indirect effects of the lox1-1 mutation on gene expression complicate the determination of exact sensing - signalling - response pathways, the results presented here outline a more refined LOX1 functioning in Cd-induced stress responses that could be used in studies determining the exact involvement of LOX1 in these pathways.
authors: Hasselt University, Environmental Biology, Centre for Environmental Sciences, Agoralaan Building D, B-3590 Diepenbeek, Belgium.
authors: Els
authors: E
authors: Keunen
authors: Tony
authors: T
authors: Remans
authors: Kelly
authors: K
authors: Opdenakker
authors: Marijke
authors: M
authors: Jozefczak
authors: Heidi
authors: H
authors: Gielen
authors: Yves
authors: Y
authors: Guisez
authors: Jaco
authors: J
authors: Vangronsveld
authors: Ann
authors: A
authors: Cuypers
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002104:Cadmium / Q000633:toxicity*; D008084:Lipoxygenase / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects* / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D002104:Cadmium; D008084:Lipoxygenase