Root-to-shoot communication plays an important role in the adaptation to environmental stress. In this study, we established a model system for root-to-shoot signalling to observe global gene expression in Arabidopsis thaliana. The roots of Arabidopsis seedlings were wounded and the expression in the shoots of 68 and 5 genes was up-regulated threefold at 30 min and 6 h post-injury, respectively. These genes were designated early and late Root-to-Shoot responsive (RtS) genes, respectively. Many of the early RtS genes were found to encode transcription factors such as AtERFs, whereas others were associated with jasmonic acid (JA) and ethylene (ET). Some of the late RtS genes were shown to be regulated by 12-oxo-phytodienoic acid (OPDA). In fact, elevated levels of JA and OPDA were detected in the shoots of seedlings 30 min and 6 h, respectively, after wounding of the roots. A mutant analysis revealed that JA and ET are involved in the expression of the early RtS genes. Thus, root-to-shoot communication for many RtS genes is associated with the systemic production of JA, OPDA and possibly ET.

It is known that wounding systemically activates the expression of various defense-related genes in plants. However, most studies of wound-induced systemic response are concerned with a leaf-toleaf response. We have recently reported that the long distance signaling was also observed in the shoots of Arabidopsis seedling with wounded roots. We identified early and late root-to-shoot responsive (RtS) genes that were upregulated in the shoots of root-wounded seedlings at 30 min and 6 h post-injury, respectively. It is likely that the primary signals were rapidly transfered from injured roots to shoots, and then these signals were converted into chemical signals. In fact, increase of JA and OPDA content activated the expression of early and late RtS genes in shoots, respectively. In addition, we visualized wound-induced root-to-shoot response by using RtS promoter-luciferase (Luc) transgenic plants. Analysis of the AtERF13 promoter::Luc transgenic plants clearly shows that the wound-induced root-to-shoot signaling was rapidly activated via the vascular systems.In higher plants, "root-to-hoot" signaling plays an important role in their adaptation in response to various environmental stresses such as dehydration, flooding, larvae attack and pathogen infection.