Control of root functions by shoot-derived gibberellin

Abstract

In plants, long-distance signaling acts as one of the mechanisms for adaptation to environmental change and growth regulation to maintain a balance between distanced organs.　Many studies suggest that gibberellins （GAs） behave as long-distance transmitters.　GA precursors can move through vascular system.　This review focuses on the functions of GA signaling between shoot and root.　Root-expressed genes which responding to shoot-derived GAs were identified by microarray analysis in Arabidopsis.　Two GA-responding genes （1） IRT1 （Iron Regulated-Transporter 1） and （2） CLE6 （CLAVATA/ESR-RELATED 6） have been identified.　IRT1 plays a key role in Fe absorption into root cells from soil.　GA promotes the gene expression of IRT1 and Fe absorption in root.　GAs would be signal transmitters for the acquirement of essential nutrients such as Fe.　CLE6 belongs to peptide hormones.　Expression of CLE6 in root is found in vascular tissue and endodermis and promoted by shoot-derived GAs.　Phenotype of GA deficient mutant shows partial recovery recovered by grafting with CLE6 overexpression transgenic line.　CLE6 is up-regulated by GAs and acts as long-distance signal for organ growth.　In conclusion, mentioned GA functions are considered essential for information exchange between shoot and root.