Mammalian CYP2E1 gene triggered changes of relative ions fluxes, CaM content and genes expression profiles in Petunia hybrida cells to enhance resistance to formaldehyde

Abstract

Cytochrome P450 CYP2E1, encoded by CYP2E1 gene, is mainly present in the mammal hepatocytes and plays important roles in metabolizing xenobiotic compounds. The CYP2E1-transgenic Petunia hybrida enhanced the resistance of Petunia against formaldehyde. In this study, we investigated the biochemical and physiological changes in CYP2E1-transgenic Petunia before and after formaldehyde stress. Non-invasive micro-test technology was applied to monitor the changes in fluxes of K+, H+ and Ca2+ ions. The changes in calmodulin (CaM) content were measured with enzyme-linked immunosorbent assay. The gene expression profiles were assayed with digital gene expression tag profiling. The steady efflux of K+ in leaf cells of CYP2E1-transgenic Petunia was higher whereas the steady efflux of H+ in leaf cells of CYP2E1-transgenic Petunia under formaldehyde stress were lower than those of the controls (wild-type and gus-transgenic Petunia). These results suggest that the capability of Petunia to resist formaldehyde stress is correlated with the steady K+ efflux rate. It could be possible that the enhanced expression of CYP2E1 greatly reduced the generation of H+ and the H+ efflux to reduce the damage to plant cells caused by oxidative stress under formaldehyde stress. Ca2+ in leaf cells of CYP2E1-transgenic Petunia exhibited efflux whereas Ca2+ in leaf cells of controls exhibited influx. CaM content in CYP2E1-transgenic Petunia was significantly higher than those in controls. Before and after formaldehyde stress, the differentially expressed sequence tags (ESTs) meeting ≥ two-fold difference, in wild-type Petunia, the up-regulated ESTs were 1344 while the down-regulated ESTs were 1516; in CYP2E1-transgenic Petunia, the up-regulated ESTs were 975 while the down-regulated ESTs were 638. Compared to those of the wild-type Petunia, after formaldehyde stress, both of up-regulated and down-regulated ESTs in CYP2E1-transgenic Petunia were significantly reduced. After formaldehyde stress, in CYP2E1-transgenic Petunia, the enzymes closely related to photosynthetic systems were all down-regulated. These results indicate that CYP2E1 can enhance the capability of Petunia to resist formaldehyde stress but it may not activate Calvin cycle during formaldehyde metabolism process.