ISOLATION OF THE B GENE: A REGULATORY LOCUS MAIZE

了解基因在发育过程中的差异调节 是生物学中的一个基本问题 的遗传学研究 玉米提供了许多基因表达程序性变化的例子 在发展过程中，并已确定的监管现象，如 副突变和控制因素的影响。 一个这样的基因 玉米中的一个特征性基因座是调控表达的B基因座 植物中的花青素色素。 组织特异性 花色素苷的合成取决于B上存在哪个等位基因。 在分子水平上检查不同的B等位基因应该可以揭示 负责调节这些蛋白质的数量、时间和 色素产生的组织特异性。 某些B等位基因经历或 促进副突变：基因表达的一种可遗传的改变， 在同一株植物中存在两个特定的等位基因。 许多模型 已经提出来解释paramutation，包括改变， 染色质结构，基因转换，或相互作用或转座 DNA元素。 这种等位基因相互作用的分子描述 应该揭示基因细胞遗传调控的一般原理 在发育过程中出现的表达。 这些原则应该是 适用于其他生物体，其中组合的遗传和分子 方法尚不可行。 该提案的长期目标是检查分子 控制玉米中B基因表达的机制。 具体 该建议的目的是使用该方法克隆B基因组序列。 转座因子Robertson突变体来标记该位点。 多 已经分离出独立的插入突变，以增加 获得完整基因的可能性。 然后基因将被恢复 通过利用插入B的元件之间的同源性 基因和克隆的转座因子。 变种人和克隆人 在这项研究中产生的序列，将提供工具，开始 在B的副突变和基因表达的分子分析。

Understanding how genes are differentially regulated during the development of an organism is a fundamental problem in biology. Genetic studies of maize have provided many examples of programmed changes in gene expression during development and have identified regulatory phenomena such as paramutation and the effects of controlling elements. One such genetically characterized locus in maize is the B locus which regulates the expression of anthocyanin pigments in the plant. Variation in the tissue-specific synthesis of anthocyanins is determined by which allele is present at B. Examining different B alleles at the molecular level should reveal nucleotide sequences responsible for regulating the quantity, timing and tissue-specificity of pigment production. Certain B alleles undergo or promote paramutation: a heritable alteration in gene expression promoted by the presence of two specific alleles in the same plant. Many models have been proposed to explain paramutation, including alteration in chromatin structure, gene conversion, or the interaction or transposition of DNA elements. A molecular description of this allelic interaction should reveal general principles on cell heritable regulation of gene expression as it occurs during development. These principles should be applicable to other organisms where a combined genetic and molecular approach is not yet feasible. The long term goals of this proposal are to examine the molecular mechanisms controlling the expression of the B gene in maize. The specific aim of this proposal is to clone the B genomic sequences using the transposable element Robertson's Mutator to mark the locus. Multiple independent insertion mutations have been isolated in order to increase the probability of obtaining the entire gene. The gene will then be recovered by taking advantage of the homology between the element inserted into the B gene and the cloned transposable element. The mutants and the cloned sequences generated in this study, will provide tools with which to begin a molecular analysis of paramutation and gene expression at B.