Salt-induced expression of peroxisome-associated genes requires components of the ethylene, jasmonate and abscisic acid signalling pathways

Peroxisomes participate in many biological functions including detoxification of reactive oxygen species and biosynthesis of oxylipin signalling molecules. Peroxisome protein and enzyme activities have been reported to change in response to salt stress. To investigate the relationship between peroxisomes and salt stress the level of expression of three peroxisome-associated genes, thiolase (PED1), PEX10 and PEX1 was analysed by quantitative real-time polymerase chain reaction. The steady-state transcript level of all three genes was increased by salt and ABA treatment, and was blocked in the abi1-1 mutant. Salt-dependent increase of transcript for all three genes also required the JAR1 gene as it was prevented in the jar1-1 mutant. Expression of thiolase, and to a lesser extent PEX1, was increased in the jar1-1 mutant in the absence of salt, suggesting jasmonate may negatively regulate these genes in the absence of salt stress. PEX1 was up-regulated in the ethylene over-producer eto1-1 and salt had an additive effect on PEX1 transcript level, but salt induction may be inhibited in the ethylene-insensitive line etr1-1. Consistent with this, PEX1 was also up-regulated in transgenic plants over-expressing the ethylene response element binding factors AtERF1 and AtERF5.