Rhizosphere Microbes Influence Host Circadian Clock Function

Abstract

The circadian clock is an important determinant of fitness that is entrained by local conditions. Aside from abiotic factors, individual pathogenic soil bacteria affect circadian clock function in plant hosts. Yet, in nature, plants interact with diverse microbial communities, and the effect of complex communities on clock function remains unclear. In Arabidopsis thaliana and its wild relative, Boechera stricta, we used diverse rhizosphere inoculates and host genotypes to test the effect of complex rhizosphere microbial communities on the host circadian clock. A. thaliana plants with an intact rhizosphere microbiome expressed a circadian period closer to 24 h in duration and significantly shorter (by 48 min on average) relative to plants grown with a disrupted microbiome. Wild-type host genotypes of A. thaliana differed in clock sensitivity to microbes, with one genotype (Landsberg erecta) expressing a 119-min difference in circadian period length across rhizosphere microbial treatments. A similar pattern of clock sensitivity to soil microbes was observed in B. stricta. Finally, rhizosphere microbes collected from the mutant genotype toc1-21 of A. thaliana with a short-period phenotype and used as inoculate significantly shortened the long-period phenotype of the clock mutant genotype ztl-1. The results indicate that complex rhizosphere microbial communities affect host clock function.