ANALYSIS OF ZEIN GENE EXPRESSION IN MAIZE

玉米的玉米醇溶蛋白基因编码种子贮藏蛋白。 玉米醇溶蛋白占胚乳蛋白的60%，由四种蛋白质组成 结构不同的类型：缺硫的阿尔法-玉米醇溶蛋白和 富含硫的贝塔、伽马和德尔塔-玉米醇溶蛋白。阿尔法-玉米醇溶蛋白被编码 一个可能有75到100个基因的多基因大家族，而贝塔基因， Gamma和Delta-Zeins各自只由一个或两个基因编码。一个 已经确定了一些突变，这些突变导致了基因的减少 α-玉米醇溶蛋白的合成。其中至少有一个，Opaque-2，对应于 一种转录调节蛋白，它可以影响 阿尔法-玉米醇溶蛋白基因家族的某些成员。然而，这些机制 其中大多数突变都会影响特定的玉米醇溶蛋白的表达 是不被理解的。 对编码基因的调控知之甚少 富含硫的玉米醇溶蛋白。最近，我们描述了一组名为 不透明-2“修饰剂”。“改良的”不透明玉米品系包含两个至 四倍于标准OPAQUE-2突变体的伽马玉米醇溶蛋白。这个 修饰物似乎是显性基因，它特别增加了 伽马醇溶蛋白基因的表达。 我们建议： (1)确定不透明-2‘修饰语’如何影响 伽马-玉米醇溶蛋白基因 (2)研究OPAQUE-2“修饰语”的遗传复杂性 鉴定和分离修饰基因 (3)检验是伽马-玉米醇溶蛋白含量高的假设 它的分布是导致玻璃体型的原因 修改后的不透明内核，以及 (4)进一步鉴定指导转录的DNA序列 阿尔法、贝塔和伽马-玉米醇溶蛋白 基因，并确定调节其转录的蛋白质。 除了扩大我们对组织特异性的理解 基因表达，这些研究的结果将应用于 提高玉米蛋白质含量和籽粒品质。

The zein genes of maize encode the seed storage proteins. Zeins constitute 60% of the endosperm protein and consist of four structurally distinct types: the sulfur-poor alpha -zeins, and the sulfur-rich beta, gamma, and delta -zeins. The alpha -zeins are encoded by a large multigene family of possibly 75 to 100 genes, while the beta, gamma, and delta -zeins are each encoded by only one or two genes. A number of mutations have been identified that cause a reduction in the synthesis of alpha -zeins. At least one of these, opaque-2, corresponds to a transcriptional regulatory protein that affects the expression of certain members of the alpha -zein gene family. However, the mechanisms by which most of these mutations affect the expression of specific zeins are not understood. Little is known about the regulation of the genes encoding the sulfur-rich zeins. Recently we characterized a group of genes called opaque-2 'modifiers.' The "modified' opaque lines of maize contain two to four times as much gamma zein as standard opaque-2 mutants. The "modifiers' appear to be dominant genes that specifically increase the expression of the gamma -zein genes. We propose to: (1) Determine how the opaque-2 'modifiers" affect the expression of gamma -zein genes (2) Investigate the genetic complexity of opaque-2 "modifiers' and begin to identify and isolate modifier genes (3) Test the hypothesis that it is the high content of gamma -zein and its distribution that are responsible for the vitreous phenotype of modified opaque kernels, and (4) Further characterize the DNA sequences that direct the transcription of alpha ,beta, and gamma -zein genes and identify the proteins regulating their transcription. In addition to expanding our understanding of tissue-specific gene expression, the results of these studies will have application to the improvement of maize protein and seed quality.