Auxin actions in regulating plant gravitropism

Gravitropism of higher plants is one of the fundamental adoptive responses upon environmental stimuli. Auxin,the most important plant hormone that is involved in almost every process of plant growth and development,has been proven to be an indispensable factor that determines the process of gravitropism. Asymmetrical auxin distribution within plant organs might explain the mechanism of tropic growth,which in turn triggers the differential expression of downstream genes.The biosynthesis,catabolism,polar transport and signal transduction of auxin are believed to play critical roles in the regulation of gravitropism as well as other tropism.This review will summarize the current status and draw perspective on the elucidation of the molecular mechanisms that auxin regulate plant gravitropism.