ebisu dwarf (d2) is a mutant caused by mutation in a rice brassinosteroid biosynthetic enzyme gene, CYP90D2/D2, thereby conferring a brassinosteroid-deficient dwarf phenotype. Three newly isolated d2 alleles derived f...ebisu dwarf (d2) is a mutant caused by mutation in a rice brassinosteroid biosynthetic enzyme gene, CYP90D2/D2, thereby conferring a brassinosteroid-deficient dwarf phenotype. Three newly isolated d2 alleles derived from a Nippon- bare mutant library (d2-3, d2-4, and d2-6) produced more severe dwarf phenotypes than the previously characterized null allele from a Taichung 65 mutant library, d2-1. Linkage analysis and a complementation test clearly indicated that the mutant phenotypes in d2-6 were caused by defects in CYP90D2/D2, and exogenous treatment with brassinolide, a bioactive brassinosteroid, rescued the dwarf phenotype of three Nipponbare-derived d2 mutants. However, the content of endogenous bioactive brassinosteroid, castasterone, and the expression of brassinosteroid-response genes indicated that partial suppression of the brassinosteroid response in addition to a brassinosteroid deficiency has occurred in the Nipponbare-derived d2 mutants. Based on these results, we discuss the possibility that wild-type Nipponbare has some defects in an unknown factor or factors related to the brassinosteroid response in rice.展开更多
Improving grain quality is a primary objective in contemporary rice breeding.Japanese modern rice breeding has developed two different types of rice,eating and sake-brewing rice,with different grain characteristics,in...Improving grain quality is a primary objective in contemporary rice breeding.Japanese modern rice breeding has developed two different types of rice,eating and sake-brewing rice,with different grain characteristics,indicating the selection of variant gene alleles during the breeding process.Given the critical importance of promptly and efficiently identifying genes selected in past breeding for future molecular breeding,we conducted genome scans for divergence,genome-wide association studies,and map-based cloning.Consequently,we successfully identified two genes,OsMnS and OsWOX9D,both contributing to rice grain traits.OsMnS encodes a mannan synthase that increases the white core frequency in the endosperm,a desirable trait for sake brewing but decreases the grain appearance quality.OsWOX9D encodes a grass-specific homeobox-containing transcription factor,which enhances grain width for better sake brewing.Furthermore,haplotype analysis revealed that their defective alleles were selected in East Asia,but not Europe,during modern improvement.In addition,our analyses indicate that a reduction in grain mannan content during African rice domestication may also be caused a defective OsMnS allele due to breeding selection.This study not only reveals the delicate balance between grain appearance quality and nutrition in rice but also provides a new strategy for isolating causal genes underlying complex traits,based on the concept of“breeding-assisted genomics”in plants.展开更多
文摘ebisu dwarf (d2) is a mutant caused by mutation in a rice brassinosteroid biosynthetic enzyme gene, CYP90D2/D2, thereby conferring a brassinosteroid-deficient dwarf phenotype. Three newly isolated d2 alleles derived from a Nippon- bare mutant library (d2-3, d2-4, and d2-6) produced more severe dwarf phenotypes than the previously characterized null allele from a Taichung 65 mutant library, d2-1. Linkage analysis and a complementation test clearly indicated that the mutant phenotypes in d2-6 were caused by defects in CYP90D2/D2, and exogenous treatment with brassinolide, a bioactive brassinosteroid, rescued the dwarf phenotype of three Nipponbare-derived d2 mutants. However, the content of endogenous bioactive brassinosteroid, castasterone, and the expression of brassinosteroid-response genes indicated that partial suppression of the brassinosteroid response in addition to a brassinosteroid deficiency has occurred in the Nipponbare-derived d2 mutants. Based on these results, we discuss the possibility that wild-type Nipponbare has some defects in an unknown factor or factors related to the brassinosteroid response in rice.
文摘Improving grain quality is a primary objective in contemporary rice breeding.Japanese modern rice breeding has developed two different types of rice,eating and sake-brewing rice,with different grain characteristics,indicating the selection of variant gene alleles during the breeding process.Given the critical importance of promptly and efficiently identifying genes selected in past breeding for future molecular breeding,we conducted genome scans for divergence,genome-wide association studies,and map-based cloning.Consequently,we successfully identified two genes,OsMnS and OsWOX9D,both contributing to rice grain traits.OsMnS encodes a mannan synthase that increases the white core frequency in the endosperm,a desirable trait for sake brewing but decreases the grain appearance quality.OsWOX9D encodes a grass-specific homeobox-containing transcription factor,which enhances grain width for better sake brewing.Furthermore,haplotype analysis revealed that their defective alleles were selected in East Asia,but not Europe,during modern improvement.In addition,our analyses indicate that a reduction in grain mannan content during African rice domestication may also be caused a defective OsMnS allele due to breeding selection.This study not only reveals the delicate balance between grain appearance quality and nutrition in rice but also provides a new strategy for isolating causal genes underlying complex traits,based on the concept of“breeding-assisted genomics”in plants.
