Molecular Genetic Analysis of Phase Change in Maize and Arabidopsis

玉米幼体和成体新梢发育阶段产生的叶片在形态、解剖和生化上是不同的。GLOSSY15(GL15)功能缺失突变导致一些幼叶(3-6叶)的表皮获得成体特征，这意味着GL15的正常功能既促进幼叶表皮特征的表达，又抑制成体特征的表达。GL15是已克隆的唯一参与调控叶片形态特定阶段差异的基因。因此，它不仅可以作为玉米特定时期细胞特性的分子标记，而且还可以作为了解这一鲜为人知的现象的分子机制的切入点。这里提出的研究将提供关于GL15的基本信息，以了解该基因的功能及其表达调控方式。通过对GL15基因在叶片发育的不同阶段和枝条生长的不同阶段的mRNA的原位分析，研究GL15的表达模式。这项表达分析还将对影响相变的突变(环境基金、TPL、TP2和TP3、d1、VP8)进行分析，以确定这些突变对表皮特性的影响是否通过GL15 mRNA的数量或表达模式的变化来调节。该基因家族的其他成员将被克隆，他们的基因组结构和表达模式将被鉴定，他们的功能将通过分离干扰其表达的突变体插入来确定。在对GL15-1ike基因进行分析的同时，波蒂格博士将通过筛选影响gl15-H突变背景中叶子1和2的身份的突变，来筛选可能与GL15功能冗余的基因。最后，Poethig博士将通过克隆拟南芥中GL15的同源基因并确定其功能丧失的表型来确定GL15在该物种中的功能。

Leaves produced during the juvenile and adult phases of shoot development in maize are morphologically, anatomically, and biochemically distinct. Loss-of-function mutations of GLOSSY15 (GL15) cause the epidermis of some juvenile leaves (leaves 3 to 6) to acquire adult characteristics, implying that GL15 normally functions both to promote the expression of juvenile epidermal traits and to repress the expression of adult traits. GL15 is the only gene involved in the regulation of phase-specific differences in leaf morphology that has been cloned. As such, it is useful not only as a molecular marker for phase-specific cell identity in maize, but also as an entry point into the molecular mechanism of this poorly understood phenomenon. The research proposed here will provide the basic information about GL15 necessary for understanding the function of this gene and the way in which its expression is regulated. The expression pattern of GL15 will be examined by in situ analysis of mRNA at different stages of leaf development, and at different stages during the growth of the shoot. This expression analysis will also be conducted on mutations that affect phase change (gef, Tpl, Tp2 and Tp3, dl, vp8) to determine if the effect of these mutations on epidermal identity is mediated by changes in the amount or expression pattern of GL15 mRNA. Other members of this gene family will be cloned, their genomic structure and expression pattern will be characterized, and their function will be determined by isolating Mutator insertions that disrupt their expression. In parallel with this analysis of GL15-1ike genes, Dr. Poethig will conduct a screen for genes that may be functionally redundant with GL15 by screening for mutations that affect the identity of leaves one and two in a gll5-H mutant background. Finally, Dr. Poethig will determine the function of GL15 in Arabidopsis by cloning the orthologue of GL15 in this species and determining its loss-of-function phenotype.