Becraft P W, Bongard-Pierce D K, Sylvester A W, Poethig R S, Freeling M
Plant Biology Department, University of California, Berkeley 94720.
Dev Biol. 1990 Sep;141(1):220-32. doi: 10.1016/0012-1606(90)90117-2.
The liguleless-1 (lg1) gene affects maize leaf development. In a normal maize leaf, a ligule and auricles separate the blade and sheath. The recessive lg1 mutation prevents formation of ligules and auricles during leaf development. To determine the timing and site of lg1 gene action, we compared development of wild-type and lg1 mutant leaves, and analyzed genetic mosaics composed of wild-type and lg1 mutant cells. In wild-type leaves the first sign of differentiation of the ligular region is a series of specialized anticlinal divisions in the adaxial epidermis. This establishes a distinct band of cells, from which the ligule arises via periclinal divisions. The anticlinal divisions preceding ligule formation are altered in the mutant; therefore, the gene acts early in development, before the periclinal divisions, and possibly during basipetal vascularization. Genetic mosaic analysis indicates that the lg1 gene has at least two functions with different tissue specificities: The Lg1+ wild-type allele acts autonomously in the adaxial epidermis for normal ligule development, and in internal tissues for auricle formation. Wild-type internal tissue in direct contact with lg1 epidermis appears able to induce the mutant epidermis to form a rudimentary ligule. The results indicate that the lg1 gene acts tissue specifically in an early step of ligule and auricle initiation.
无叶舌-1（lg1）基因影响玉米叶片发育。在正常玉米叶片中，叶舌和叶耳将叶片和叶鞘分隔开。隐性lg1突变会阻止叶片发育过程中叶舌和叶耳的形成。为了确定lg1基因作用的时间和位点，我们比较了野生型和lg1突变体叶片的发育情况，并分析了由野生型和lg1突变体细胞组成的遗传嵌合体。在野生型叶片中，叶舌区域分化的第一个迹象是近轴表皮中一系列特殊的垂周分裂。这形成了一条独特的细胞带，叶舌通过平周分裂从该细胞带产生。突变体中叶舌形成之前的垂周分裂发生了改变；因此，该基因在发育早期起作用，在平周分裂之前，可能在向基维管束形成过程中起作用。遗传嵌合体分析表明，lg1基因至少具有两种不同组织特异性的功能：Lg1 +野生型等位基因在近轴表皮中自主发挥作用，以实现正常的叶舌发育，并在内层组织中发挥作用以形成叶耳。与lg1表皮直接接触的野生型内层组织似乎能够诱导突变体表皮形成一个雏形叶舌。结果表明，lg1基因在叶舌和叶耳起始的早期阶段具有组织特异性作用。
