Panicle architecture in rice can have a strong influence on yield. Using N-methyl-N-nitrosourea mutagenesis, we isolated an erect panicle mutant, Hep, from Hwasunchalbyeo, a glutinous japonica rice cultivar. Genetic analysis revealed that the erect panicle phenotype was controlled by a single recessive mutation designated erect panicle 3 (ep3). Genetic mapping revealed that the ep3 mutation was located on the short arm of chromosome 2 in a 0.1 cM region delimited by the STS markers STS5803-5 and STS5803-7. The ep3 locus corresponded to 46.8 kb region and contained six candidate genes. Comparison of the DNA sequences of the candidate genes from wild-type and erect panicle plants revealed a single base-pair change in the second exon of LOC_Os02g15950, which is predicted to result in a nonsense mutation. LOC_Os02g15950 encodes a putative F-box protein containing 515 amino acids and is expressed throughout the plant during all growth stages. A line carrying a T-DNA insertion in LOC_ Os02g15950 was obtained and shown to have the same phenotype as the ep3 mutant, thus confirming the identification of LOC_Os02g15950 as the ERECT PANICLE 3 (EP3) gene. The ep3 mutation causes a significant increase in the number of small vascular bundles as well as the thickness of parenchyma in the peduncle, which results in the erect panicle phenotype.
穗型對水稻產(chǎn)量有很大影響。使用N-甲基-N-亞硝基脲處理粳型粘稻品種Hwasunchalbyeo，獲得一個直立穗突變體Hep，遺傳分析表明該表型受一個隱型突變基因ep3控制。遺傳作圖揭示ep3位于第2染色體短臂上STS標記STS5803-5和STS5803-7之間的0.1cM區(qū)間。ep3位點對應(yīng)的46.8kb區(qū)間，包含6個侯選基因。通過DNA序列比較，發(fā)現(xiàn)與野生型相比，突變體的LOC_Os02g15950基因第2外顯子有個單堿基突變，推測這是一個無義突變。LOC_Os02g15950編碼一個由515氨基酸組成的F-box蛋白，在整個生育期整個植株都有表達。一個T-DNA插入LOC_Os02g15950的突變體表現(xiàn)出與ep3相同的表型，這進一步確認了LOC_Os02g15950就是EP3。ep3突變顯著增加了小維管束的數(shù)量和穗軸的粗壯度，這是產(chǎn)生直立穗表型的原因。