In cereal breeding, semi-dwarfness and an increased spikelet number are favorable characteristics. We show that the rice DENSE PANICLE 1 (DN1) mutant allele Dn1-1 causes both of these characteristics and that Dn1-1 is a loss-of-function mutation. DN1 is allelic to DENSE AND ERECT PANICLE 1 (DEP1) (=qPE9-1). The expression level of OsCKX2 in the shoot apex of Dn1-1 plants is similar to that in the wild type, indicating that OsCKX2 does not contribute to an increased number of spikelets. A comparison of the Dn1-1 and Dn1-3 alleles suggests that the N-terminal region of DN1 contains a coiled-coil domain and a nuclear localization signal that might be responsible for semi-dwarfness. This comparison also revealed that a single transmembrane alpha-helix, a VWFC module, and a four-disulfide core domain can further increase spikelet number. Subcellular localization analysis of the DN1 protein fused with green fluorescent protein (GFP) implies that DN1 is located in the nucleus and cell membrane and that its N-terminal fragment is cleaved. Dn1-1 plants have normal sensitivity to gibberellin, brassinolide, and kinetin, and we observed no genetic epistasis with brassinolide-related mutants, suggesting that DN1 does not function in the signaling pathways of these phytohormones.
在禾谷類作物育種中，半矮稈和穗粒數(shù)增加是有利特征。我們發(fā)現(xiàn)DENSE PANICLE 1 (DN1)功能缺失突變體Dn1-1，導(dǎo)致植株半矮化和穗粒數(shù)增加。DN1與DEP1（=qPE9-1）基因是等位的。Dn1-1突變體中頂端生長(zhǎng)點(diǎn)OsCKX2的表達(dá)水平與野生型類似，表明OsCKX2可能不是造成穗粒數(shù)增加的原因。通過比較Dn1-1和Dn1-3兩個(gè)等位突變，發(fā)現(xiàn)DN1 N端包含的卷曲螺旋結(jié)構(gòu)域和核定位信號(hào)可能是引起半矮化表型的原因，另外通過比較還發(fā)現(xiàn)一個(gè)跨膜α-螺旋、VWFC模塊和four-disulfide核心結(jié)構(gòu)域能夠增加穗粒數(shù)。亞細(xì)胞定位分析表明DN1蛋白和去除N端的片段都能定位在核和細(xì)胞膜上。Dn1-1對(duì)赤霉素、油菜素內(nèi)酯、激動(dòng)素表現(xiàn)出正常的敏感性，并且Dn1-1和一些油菜素內(nèi)酯突變體間沒有遺傳上位性，表明DN1行使功能可能與這些植物激素?zé)o關(guān)。