OsHox4 regulates GA signaling by interacting with DELLA-like genes and GA oxidase genes in rice

Gibberellic acid (GA) plays an essential role in many plant growth and developmental processes. Overexpression of rice (Oryza sativa L.) HOMEOBOX4 (OsHox4) gene in rice variety IR64 under the control of CaMV 35s promoter caused varying degrees of dwarfism and bushy tillers. Further investigation showed that over-expression of OsHox4 in indica rice induced semi-dwarf by repressing stems cell elongation. This repression could be eliminated by exogenously applied Gibberellin-4 (GA4) suggested that OsHox4 was involved in GA metabolism. Investigations of the expressions of rice DELLA-like subfamily genes, GA 3-oxidase family genes and GA 2-oxidase family genes by qRT-PCR showed that OsHox4 played an important role in GA deactivation and signaling by controlling the expression of rice DELLA-like subfamily genes, rice GA 2-oxidase family genes and rice GA 3-oxidase family genes. Our experiment provided an evidence that over-expression of OsHox4 in transgenic rice resulted in a semi-dwarf phenotype that could be fully rescued by application of exogenous GA4. The OsHox4 plays an important role in GA deactivation by controlling the expression of rice DELLA subfamily genes, rice GA 2-oxidase family genes and rice GA 3-oxidase family genes.