Harper L, Freeling M
Department of Plant Biology, University of California, Berkeley 94720, USA.
Genetics. 1996 Dec;144(4):1871-82. doi: 10.1093/genetics/144.4.1871.
The maize ligule is an adaxial membranous structure on the leaf that develops at the boundary of the sheath and blade. The ligule and the associated auricle are dispensable structures, amenable to genetic manipulation. We present here a genetic analysis of liguleless1 (lg1) and liguleless2 (lg2), the two genes known to be uniquely necessary for ligule and auricle development. We show that both reference mutant alleles, lg1-R and lg2-R, are null alleles. The double mutant phenotype suggests that lg1 and lg2 act in the same pathway. Indeed, the dosage of a functional allele at either gene affects the null phenotype of the other. While lg1 function has previously been shown to be cell-autonomous, here we show that the lg2-R phenotype is cell-nonautonomous, suggesting lg1 and lg2 play different roles in the ligule-auricle induction mechanism. We present a model in which early lg2 function specifies the precise position where ligule and auricle will develop. Later lg2 function interacts with lg1 function (either directly or indirectly) to transmit and receive a make-ligule-make-auricle inductive signal.
玉米叶舌是叶片上位于叶鞘和叶片交界处发育的近轴膜状结构。叶舌和相关的叶耳是可有可无的结构，适合进行遗传操作。我们在此展示了对叶舌缺失1（lg1）和叶舌缺失2（lg2）的遗传分析，这两个基因是已知的叶舌和叶耳发育唯一必需的基因。我们表明，两个参考突变等位基因lg1-R和lg2-R都是无效等位基因。双突变体表型表明lg1和lg2在同一途径中起作用。实际上，任一基因上功能等位基因的剂量都会影响另一个基因的无效表型。虽然之前已表明lg1功能是细胞自主的，但我们在此表明lg2-R表型是非细胞自主的，这表明lg1和lg2在叶舌-叶耳诱导机制中发挥不同作用。我们提出了一个模型，其中早期lg2功能指定叶舌和叶耳将发育的精确位置。后期lg2功能与lg1功能（直接或间接）相互作用，以传递和接收形成叶舌-形成叶耳的诱导信号。
