Effects Of Phlorizin Accumulation On Auxin Distribution In Apple Plants(Malus Domestica)

Auxin is an essential hormone for plants growth and development.It can be distributed in different concentrations in different tissues of the plant through polar transport,thus precisely regulating all aspects of plant growth and development.Phlorizin is a kind of dihydrochalcone compound,the most abundant phenolic compound in Malus plants,and plays an important role in regulating the growth and development of apple plants.Previous studies have shown that the growth and development of apple plants are severely inhibited when the biosynthesis of phlorizin is suppressed,suggesting that phlorizin may affect the metabolism and/or distribution of auxin in apple plants.However,to date,the specific effects of phlorizin accumulation on auxin distribution in apple plants are not known.Therefore,in this study,we obtained two transgenic apple plants with visualized auxin distribution by using apple transgenic technology and the auxin specific response system DR5v2::GFP to express DR5v2::GFP alone in apple plants,or silence the Md UGT88F1 gene,a key gene for phlorizin synthesis,and overexpress DR5v2::GFP at the same time in apple plants.The differences in GFP signals in the root tips and leaves of the two transgenic plants were then observed using a confocal laser scanning microscope.Finally,the effects of phlorizin accumulation on auxin distribution in apple plant was resolved.The main results of the study are as follows:1.Six DR5v2::GFP transgenic apple lines were obtained,and treated with the exogenous IAA,the auxin efflux inhibitor NPA and the auxin influx inhibitor NOA.It was found that the auxin specific response promoter DR5v2 was able to respond sensitively to auxin changes in apple plants without affecting the normal growth and development of the plants,and corresponding changes of GFP signaling were observed in leaves and roots.2.Two MdUGT88F1-RNAi-DR5v2::GFP transgenic apple lines were obtained,and the transgenic plants were found to have significantly reduced phlorizin content,and the plant growth and development were significantly inhibited,with significant plant dwarfing compared to wild type and transgenic apple plants expressing DR5v2::GFP alone.Using the DR5v2::GFP transgenic apple plants as a control,it was found that the decrease in phlorizin accumulation in Md UGT88F1-RNAi-DR5v2::GFP transgenic apple plants resulted in weaker auxin signals in the root tip and leaf.In conclusion,our results showed that phlorizin accumulation can influence the distribution of auxin in apple plants,thereby regulating the growth and development process of apple plants.