Flavonoids affect the endophytic bacterial community in leaves with increasing altitude.

Altitude affects plant growth and metabolism, but the effect of altitude on plant endophytic microorganisms is still unclear. In this study, we selected 16 trees to study the response of leaves' endophytes to flavonoids and altitude (from 530 m to 1,310 m). HPLC results showed that flavonoids in leaves increased by more than 150% with attitude rising from 530 m to 1,310 m, which revealed a positive correlation with altitude. might regulate the increased flavonoids in leaves to resist the increasing light intensity. 16S rDNA sequencing results showed that the endophytic bacterial communities of at different altitudes significantly differed. leaf endophytes' alpha diversity decreased with increasing flavonoids content and altitude. The increased flavonoids might increase the environmental pressure on endophytes and affect the endophytic community in leaves. The bacterial network in leaves became more complex with increasing altitude, which might be one of the strategies of leaf endophytes to cope with increasing flavonoids. Metagenomes results predicted with PICRUSt showed that the abundance of flavonoid biosynthesis and photosynthesis genes were significantly decreased with the increase of flavonoid contents. High flavonoid content in leaves appeared to inhibit microbial flavonoid synthesis. Our findings indicate that altitude can modulate microbial community structure through regulating plant metabolites, which is important to uncovering the interaction of microbes, host and the environment.