PnF3H, a flavanone 3-hydroxylase from the Antarctic moss Pohlia nutans, confers tolerance to salt stress and ABA treatment in transgenic Arabidopsis

Flavonoids are widely distributed secondary metabolites in plants. However, far less research has been carried out on genes involved in the flavonoid biosynthetic pathways in bryophytes. Here, a novel flavanone 3-hydroxylase gene (PnF3H) was cloned from Antarctic moss Pohlia nutans. Subcellular localization revealed that PnF3H were mainly distributed to cytosol. The expression of PnF3H was rapidly induced by salt, UV-B, cold and drought stresses as well as by exogenously applied abscisic acid (ABA). Transgenic Arabidopsis plants of overexpressing PnF3H exhibited enhanced tolerance to salt and oxidative stresses. The expression levels of several stress resistance genes (i.e., AtSOS3, AtP5CS1, AtHKT1, AtCAT1 and AtAPX1) were markedly up-regulated in transgenic plants. The activities of antioxidant enzymes were increased, while the content of hydrogen peroxide was obviously decreased in PnF3H transgenic plants. Meanwhile, the expression levels of ABA-responsive genes which confer for controlling seeds germination, such as AtABI4, AtABI5, AtABI3 and AtABF3 were markedly decreased. Additionally, overexpressing PnF3H alleviated the inhibitory effects of naringenin on plant growth and changed the flavonoid components in transgenic plants. Therefore, we proposed that PnF3H was a flavanone 3-hydroxylase involving in regulating the salinity tolerance and ABA sensitivity to enable P. nutans to adapt to polar climates.