Study On The Molecular Mechanism Of OsHLS1 Regulating Rice Plant Height Developmen

Plant height is an important factor affecting rice yield.Gibberellin（GA）synthesis and metabolism and signal transduction pathways play an important role in rice plant height development.The rice gene OsHLS1 is significantly induced by GA,but the specific biological function and the molecular mechanism of the gene are not clear.In this study,OsHLS1 overexpression lines,mutant lines and wild type lines were used as research materials to reveal the biological function and the molecular mechanism of this gene in rice plant height development.The main results are as following:（1）OsHLS1 belongs to the HLS family,and its expression is up-regulated by gibberellin（GA）,abscisic acid（ABA）,auxin（IAA）and abiotic stress.（2）OsHLS1 is involved in regulating rice internode growth and plant height development.The mutant lines（oshls1-3）showed early flowering/early senescence,poor pollen development,and decreased seed setting rate.（3）OsHLS1 is involved in GA pathway regulating plant height development in rice.Compared with the wild type,overexpression lines（OE6）and mutant lines（oshls1-3）were more sensitive to exogenous GA₃,and less sensitive to the gibberellin synthesis inhibitor PAC.（4）OsHLS1 affected the accumulation of active GA in rice.Compared with wild type,the down-regulated expression of GA synthesis-related genes in OE6 and oshls1-3 lines led to a decrease in endogenous GA content.（5）OsHLS1 regulates the transcriptional expression of gibberellin metabolism genes OsGA2ox3 and EUI1 by interacting with IPA1 and OsTB1 and forming a protein complex with OsMADS57.OsHLS1 forms a protein complex with IPA1,OsTB1 and OsMADS57.When OsHLS1 is present,the complex enhances the transcriptional expression of the downstream target gene OsGA2ox3 of the transcription factor OsMADS57,and promotes the conversion of active GA to inactive GA,resulting in a semi-dwarf phenotype of rice plant height.When the function of OsHLS1 is lost,the protein complex enhances the transcriptional expression of the downstream target gene EUI1 of the transcription factor OsMADS57,promotes the transformation of active GA to inactive GA,and causes the phenotype of rice plant height dwarfing.In summary,this study preliminaries elucidated the specific biological function of OsHLS1 in rice and its molecular mechanism involved in the regulation of rice plant height development by a gibberellin pathway.This study will provide a theoretical basis for the use of modern molecular biology and genetics to improve rice plant type breeding.