Increment of Ascorbate peroxidase and metalothionin gene expressions by the cold stress in varieties of rape (Brassica napus)

The rape (Brassica napus) is an economically valuable plant shose tolerance to stresses has always drown concern. It is well known that، the cold (0-20 °C) and freezing (<0 °C) stresses can influence growth and productivity of the farm plants and the degree of impressionability is dependent on the type of stresses، genetics of the plants and the resistance mechanisms. In this investigation، the varieties of SLMO46 and Quantum were evaluated as resistant and sensitive varieties، respectively، against low temperature stresses. One of the effective factors in plant resistance to the stresses is quantity of the ascorbate peroxidase (APX) and the metallothionein (MTL) in the plant tissues. The ascorbate peroxidase activity in the SLMO46 tissues was more than Quantum and the activity was increased about two times during the cold stress. Quantitave analysis of Apx2 and Mtl genes expression according to 2-ΔΔCt showed that the quantities were 2. 1 and 9. 1 in the SLMO46 and 1. 8 and 5. 2 in the Quantum، respectively. The data indicated that under normal condition، the enzyme activity in the resistant plants was more than the sensitive one and the stress can induce about 60% increment in the enzyme activity.