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.
在禾谷类作物育种中，半矮秆和穗粒数增加是有利特征。我们发现DENSE PANICLE 1 (DN1)功能缺失突变体Dn1-1，导致植株半矮化和穗粒数增加。DN1与DEP1（=qPE9-1）基因是等位的。Dn1-1突变体中顶端生长点OsCKX2的表达水平与野生型类似，表明OsCKX2可能不是造成穗粒数增加的原因。通过比较Dn1-1和Dn1-3两个等位突变，发现DN1 N端包含的卷曲螺旋结构域和核定位信号可能是引起半矮化表型的原因，另外通过比较还发现一个跨膜α-螺旋、VWFC模块和four-disulfide核心结构域能够增加穗粒数。亚细胞定位分析表明DN1蛋白和去除N端的片段都能定位在核和细胞膜上。Dn1-1对赤霉素、油菜素内酯、激动素表现出正常的敏感性，并且Dn1-1和一些油菜素内酯突变体间没有遗传上位性，表明DN1行使功能可能与这些植物激素无关。