BACKGROUND

Flavonoid biosynthesis pathway is generally thought unique to land plants and has assisted plants to adapt the terrestrial ecosystems. In this pathway, four 2-oxoglutarate/Fe(II)-dependent dioxygenases (2-ODDs), i.e., flavone synthase I (FNSI), flavanone-3-hydroxylase (F3H), flavonol synthase (FLS) and anthocyanin synthase/leucoanthocyanidin dioxygenase (ANS/LDOX), catalyze the hydroxylation and desaturation reactions. In bryophytes, the earliest land plant group, little is known about the biological functions of these enzymes.

RESULTS

Here, we cloned a Pn2-ODD2 gene of flavonoid biosynthesis pathway from Antarctic moss Pohlia nutans, which was induced by exogenous NaCl, PEG and abscisic acid (ABA) treatment. Overexpression of Pn2-ODD2 increased the drought resistance in Physcomitrium patens and Arabidopsis thaliana during gametophyte growth and seed germination, respectively. Overexpressed-Pn2-ODD2 Arabidopsis also exhibited the enhanced tolerance to oxidative stress, with the downregulation of ROS generation gene and increased the total flavonoid content. Also, overexpression of Pn2-ODD2 decreased the ABA sensitivity in transgenic P. patens and Arabidopsis. Meanwhile, overexpression of Pn2-ODD2 resulted in an increase in both anthocyanins and flavonols in Arabidopsis, which was correlated with the up-regulated anthocyanin biosynthesis gene.

CONCLUSIONS

Taken together, Pn2-ODD2 conferred the resistance to drought and oxidative stress by regulating antioxidant defense system in plants.