Molecular Genetic Analysis of Phase Change in Maize and Arabidopsis

在玉米芽发育的幼年期和成年期产生的叶在形态学、解剖学和生物化学上是不同的。GLOSSY 15（GL 15）的功能丧失突变导致一些幼叶（叶3至6）的表皮获得成年特征，这意味着GL 15通常既促进幼叶表皮特征的表达又抑制成年特征的表达。GL 15是唯一一个参与调控叶形态阶段特异性差异的基因。因此，它不仅可用作玉米中阶段特异性细胞身份的分子标记，而且可作为进入这种知之甚少的现象的分子机制的切入点。这项研究将为了解该基因的功能及其表达调控方式提供必要的有关GL 15的基本信息。将通过在叶发育的不同阶段和在芽生长期间的不同阶段的mRNA的原位分析来检查GL 15的表达模式。还将对影响相变的突变（gef、Tpl、Tp 2和Tp 3、dl、vp 8）进行该表达分析，以确定这些突变对表皮特性的影响是否由GL 15 mRNA的量或表达模式的变化介导。该基因家族的其他成员将被克隆，其基因组结构和表达模式将被表征，并且其功能将通过分离破坏其表达的突变体插入来确定。在对GL 15 - 1样基因进行分析的同时，Poethig博士将通过筛选在gl 15-H突变体背景中影响叶子1和2的同一性的突变来筛选可能与GL 15功能冗余的基因。最后，Poethig博士将通过克隆GL 15在该物种中的直系同源物并确定其功能丧失表型来确定GL 15在拟南芥中的功能。

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.