Sugar acts as a regulatory signal on the wound-inducible expression of<Emphasis Type="Italic"> SbHRGP3</Emphasis>::<Emphasis Type="Italic">GUS</Emphasis> in transgenic plants

SbHRGP3 encodes an HRGP whose expression is correlated with the cessation of root elongation in soybean. The wound-inducible expression of SbHRGP3 interestingly requires sucrose although wounding alone induces the expression of many HRGP genes. To examine whether sugar serves as a specific signal on the wound-inducible expression or whether sugar is required to provide ATP, we examined SbHRGP3::GUS expression in transgenic tobacco plants. Various oligosaccharides including non-metabolizable sugar induced SbHRGP3::GUS expression in transgenic plants. The inhibitors of photosynthesis and of cellular respiration did not affect the wound-inducible expression of SbHRGP3::GUS. However, the induction was significantly affected by PCMBS, an inhibitor of active apoplastic phloem loading of sucrose, suggesting that SbHRGP3::GUS expression in phloem tissues requires translocated sucrose. We therefore propose that sugar acts as a specific regulatory signal on the wound-inducible expression of SbHRGP3, rather than acting as a simple provider of ATP.Abbreviations ATP Adenosine triphosphate - DCMU 3-(3,4-Dichlorophenyl)-1,1-dimethylurea - DTT Dithiothreitol - HRGP Hydroxyproline-rich glycoprotein - GUS -Glucuronidase - MU 4-Methylumbelliferone - MUG 4-Methylumbelliferyl ß-glucuronide - PCMBS p-Chloromercuribenzenesulphonic acidCommunicated by I.S. Chung