EXPRESSION OF C4 GENES IN DEVELOPMENT OF LEAF CELL TYPES

我们的长期目标是了解 发育中的叶片产生基因表达的空间模式 对于它们后来的功能来说是必不可少的。我们对补体C4表达的研究 玉米叶片发育过程中的途径基因表明，每个叶脉 是周围细胞表达的早期组织中心。 不同的C4基因在静脉的近端和远端表达，在 最终将表达限制在束鞘的空间模式 (BS)和叶肉(M)细胞，分别位于近和远位置。 C4基因的同源基因在C3植物中非特异性表达。 这项提议试图确定这些现象的分子基础， 具体目标如下： (1)测定C4基因表达与细胞成熟度的依赖关系 在不同细胞年龄的叶片中，使用C4报告程序分析细胞位置 和安排， (2)确定特定细胞所需的调控要素 依赖NADP的苹果酸基因的位置依赖性表达 酶(ME，BS特异性)和NADP依赖的苹果酸脱氢酶(MDH， M特异性)，使用原生质体和完整叶片中的表达分析， 和 (3)确定C4基因是否与C3基因不同 通过空间响应元素的存在，或者C4和C3 解剖结构提供了不同的空间信号，从根本上说相似 基因。 这些研究将得到我们在现场分析的经验的帮助 基因在叶片中的表达，由我们广泛收集的 C4抗体、cDNA和基因探针，以及叶片中的自然差异 玉米、黄曲霉和Arundinella C4和类C4之间的细胞排列 物种。

Our long term objectives are to understand the mechanisms by which developing leaves produce the spatial patterns of gene expression essential for their later function. Our studies of the expression of C4 pathway genes during maize leaf development have indicated that each vein is an early organizing center for expression in surrounding cells. Different C4 genes are expressed proximal and distal to the vein, in a spatial pattern that eventually restricts expression to bundle sheath (BS) and mesophyll (M) cells at near and far locations, respectively. Homologs of the C4 genes are expressed non-specifically in C3 plants. This proposal seeks to determine the molecular basis of these phenomena, with the following specific aims: (1) to measure the dependence of C4 gene expression on cell maturity and cell position, using C4-reporter assays in leaves with various cell ages and arrangements, (2) to characterize the regulatory elements required for cell-specific and position-dependent expression of genes for NADP-dependent malic enzyme (ME, BS-specific) and NADP-dependent malate dehydrogenase (MDH, M-specific), using expression assays in protoplasts and intact leaves, and (3) to determine whether the C4 genes differ from their C3 counterparts by the presence of spatial response elements or whether C4 and C3 anatomies provide different spatial signals to fundamentally similar genes. These studies will be aided by our experience with in situ analysis of gene expression in leaves, by our extensive collection of characterized C4 antibody, cDNA, and gene probes, and by natural differences in leaf cell arrangements among maize, Flaveria, and Arundinella C4 and C4-like species.