Establishment of a simple Agrobacterium rhizogenes-mediated hairy root transformation system in sour jujube

Jujube (Ziziphus jujuba Mill.) is an important fruit tree in China. However, due to the high heterozygosity of jujube, the gene transformation system is not maturely established. With the development of A. rhizogenes mediated transformation technology, it was successfully applied to genetic transformation in different woody plant species, which can be employed for gene transformation in jujube. Thus, in order to establish an efficient transformation system for jujube, we obtained hairy roots by infecting sour jujube seedlings with A. rhizogenes which contained 35S::GUS-ZjMAPKK4 vector under a non-sterile environment, and different treatments on the induction of 35S::GUS-ZjMAPKK4 hairy roots. The results showed that the hypocotyls of 2-week-old sour jujube seedlings infested with 0 mM AS concentration, which were cultivated at dark condition for 12 h, the transformation efficiency was the highest that the transformed gene hairy roots were successfully induced. Furthermore, to confirm the whether ZjMAPKK4 integrated into genome of the hairy roots, the GUS histochemical staining and qRT-PCR analysis were conducted. It showed that the transgenic ZjMAPKK4 hairy roots from two growth periods were successfully stained with blue, whereas the wild-type roots from the non-infested seedlings were not stained blue. The relative expression of ZjMAPKK4 and GUS gene was significantly higher than that in the wild-type plants, reaching more than 10-folds and 200-folds, respectively. Finally, the transformation efficiency reached 0.66 %. All the results demonstrated that we established a simple A. rhizogenes-mediated hairy root transformation system in sour jujube, which could be used for functional validation analysis of jujube biological genes.