Kyozuka J, Konishi S, Nemoto K, Izawa T, Shimamoto K
Laboratory of Plant Molecular Genetics, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, 630-01 Japan.
Proc Natl Acad Sci U S A. 1998 Mar 3;95(5):1979-82. doi: 10.1073/pnas.95.5.1979.
FLORICAULA (FLO) of Antirrhinum and LEAFY (FLY) of Arabidopsis regulate the formation of floral meristems. To examine whether same mechanisms control floral development in distantly related species such as grasses, we isolated RFL, FLO-LFY homolog of rice, and examined its expression and function. Northern analysis showed that RFL is expressed predominantly in very young panicle but not in mature florets, mature leaves, or roots. In situ hybridization revealed that RFL RNA was expressed in epidermal cells in young leaves at vegetative growth stage. After the transition to reproductive stage, RFL RNA was detected in all layers of very young panicle including the apical meristem, but absent in the incipient primary branches. As development of branches proceeds, RFL RNA accumulation localized in the developing branches except for the apical meristems of the branches and secondary branch primordia. Expression pattern of RFL raised a possibility that, unlike FLO and LFY, RFL might be involved in panicle branching. Transgenic Arabidopsis plants constitutively expressing RFL from the cauliflower mosaic virus 35S promoter were produced to test whether 35S-RFL would cause similar phenotype as observed in 35S-LFY plants. In 35S-RFL plants, transformation of inflorescence meristem to floral meristem was rarely observed. Instead, development of cotyledons, rosette leaves, petals, and stamens was severely affected, demonstrating that RFL function is distinct from that of LFY. Our results suggest that mechanisms controlling floral development in rice might be diverged from that of Arabidopsis and Antirrhinum.
金鱼草的花椰菜（FLO）和拟南芥的叶状（FLY）调控花分生组织的形成。为了研究是否相同的机制控制诸如禾本科等远缘物种的花发育，我们分离了水稻的FLO-LFY同源物RFL，并检测了其表达和功能。Northern分析表明，RFL主要在非常幼嫩的幼穗中表达，而在成熟小花、成熟叶片或根中不表达。原位杂交显示，在营养生长阶段，RFL RNA在幼叶的表皮细胞中表达。过渡到生殖阶段后，在包括顶端分生组织在内的非常幼嫩的幼穗的所有层中都检测到了RFL RNA，但在初生分支的起始部位没有。随着分支的发育，RFL RNA积累定位于发育中的分支中，除了分支的顶端分生组织和二级分支原基。RFL的表达模式提出了一种可能性，即与FLO和LFY不同，RFL可能参与幼穗分支。构建了组成型表达来自花椰菜花叶病毒35S启动子的RFL的转基因拟南芥植株，以测试35S-RFL是否会导致与35S-LFY植株中观察到的类似表型。在35S-RFL植株中，很少观察到花序分生组织向花分生组织的转变。相反，子叶、莲座叶、花瓣和雄蕊的发育受到严重影响，表明RFL的功能与LFY不同。我们的结果表明，控制水稻花发育的机制可能与拟南芥和金鱼草的不同。
