Map-based Cloning And Functional Analysis Of SHG1,A Grain Shape Regulator In Rice

Rice is one of the most important food crops of the world.As one of the pivotal factors in determining yield,several genes controlling grain size had been cloned.However,the molecular mechanism of grain shape is still not clear.Here we report a rice grain shape mutant short grain](shgl),isolated by EMS mutagenesis,which exhibit short and round grains.To explore the molecular mechanism of SHG1 in determininig grain shape,several experiments had been applied.The main results are as following:1.shgl mutant exhibits longer,wider but thicker seeds compared with the wild-type,and 1000-Grain weight was significantly decreased in shgl as well.Cytological analysis indicated that the short grain phenotype may be caused by the inhibition of cell size.2.Map-based cloning reveal that SHGl encoded an OsKinesin protein.The kinesin motor domain in SHGl is highly conserved in higher plant.3.The plants with overexpressed SHGl in shgl mutant exhibit longer,wider but less thicker seeds than the wild-type,those changed characters led to 1000-grain weight in transgenic lines is lower than wild-type,but higher than shgl mutant.4.SHGl is ER-located(endoplasmic reticulum-located)and widely distributed in various organs.Meanwhile,transcriptome analysis revealed that thousands of genes are differentially expressed between WT and shgl.Those genes are divided into several groups based on GO classification,like metabolic process,primary metabolic process,cellular protein modification process,etc.In addition,RT-qPCR revealed that the expression of several cell cycle genes were changed in shgl,that is correlated with the shorten cell size in shgl.5.A few auxin response element were found in SHGl promoter and SHGl is up-regulated by exogenous IAA,therefore,we speculated whether auxin signal is involved in shgl phenotype regulation.We firstly found shgl is insensitive in root elongating under a 0.01?M exogenous IAA feeding compare with the wild type.Then we tested OsARFs binding SHGl promoter region by dual luciferase assay.6.We tested the sensitivity of WT and shgl to 24-epi-brassionlide by three methods and found that shgl is less sensitive to exogenous BL.Moreover,altered expression of BR response genes were found in shgl mutant.Further analysis show that exogenous BR repress SHGl in the wild type.