摘要
Flavonoids play important roles in regulating plant growth and development.In this study,three kaempferol 3-O-glycosides were identi fi ed and mainly accumulated in fl owers but not in leaves or fruits of Malus.In Malus,fl ower petal color is normally white,but some genotypes have red fl owers containing anthocyanin.Anthocyanin biosynthesis appears to be in competition with kaempferol 3-O-glycosides production and controlled by the biosynthetic genes.The white fl ower Malus genotypes had better-developed seeds than the red fl ower genotypes.In fl owers,the overexpression of MYB10 in Malus domestica enhanced the accumulation of anthocyanin,but decreased that of kaempferol 3-O-glycosides.After pollination the transgenic plants showed slower pollen tube growth and fewer developed seeds.Exogenous application ofdifferent fl avonoid compounds suggested that kaempferol 3-O-glycosides,especially kaempferol 3-O-rhamnoside,regulated pollen tube growth and seed set rather than cyanidin or quercetin 3-O-glycosides.It was found that kaempferol 3-O-rhamnoside might regulate pollen tube growth through effects on auxin,the Rho of plants(ROP)GTPases,calcium and the phosphoinositides signaling pathway.With the inhibition of auxin transport,the transcription levels of Heat Shock Proteins(HSPs)and ROP GTPases were downregulated while the levels were not changed or even enhanced when blocking calcium signaling,suggesting that HSPs and ROP GTPases were downstream of auxin signaling,but upstream of calcium signaling.In summary,kaempferol glycoside concentrations in pistils correlated with auxin transport,the transcription of HSPs and ROP GTPases,and calcium signaling in pollen tubes,culminating in changes to pollen tube growth and seed set.
基金
This work was funded by the National Key R&D Program(2018YFD1000200)
the National Natural Science Foundation(31972366)of China。
