Regulation of Period and Pattern of Vegetative Development in Maize

从营养（无限）生长到生殖（有限）生长的转变是高等植物茎发育的一个主要转变。 这种转变发生在茎尖分生组织，该区域启动原基，在营养发育期间分化为由茎组织分离的叶，或在生殖发育期间分化为花器官。 这种转变的时机对芽的结构有着深远的影响，也影响着作物的产量。 调节植物向开花过渡的机制开始被理解，植物的过渡是对环境信号的反应。 然而，许多其他植物在各种环境中开花。 在这些植物中，据信从营养生长到开花的过渡时间的主要决定因素是发育程序，对此知之甚少。 这里提出的实验的目的是检查的各个方面的发展计划背后的开关开花植物的后一组，玉米。 分生组织从植物的其他地方接收信息，并通过继续叶片分化（不确定）或确定有限生长并形成花序（雄穗）来做出反应。 该研究者将通过器官培养技术检查该信息的潜在来源。 这些实验将为最终识别信号奠定基础，这些信号通过个体发育告知分生组织的进展，从而精确调节玉米芽的形态。 玉米营养枝顶端分生组织被推断为组织成层，其中通常分生组织的最低细胞（在外围）将产生植物的第一形成的节，中间分生组织细胞产生植物的较晚的节，并且上部细胞产生植物的顶部。 最有可能参与再生结构形成的细胞位于分生组织的顶端。 通过切除和培养重新设置分生组织导致由分生组织形成的节比正常情况下形成的节更多。 这样做的一个不可避免的结果是，分生组织中至少一些细胞对芽的贡献发生变化。 本研究将使用克隆分析来确定复位植物的额外节点的分生组织内的起源。 这些信息将有助于理解分生组织内细胞相对于它们将贡献的植物部分的灵活性，以及当分生组织通过切除和培养重置时发生的重组的性质。 这也可能对通过茎分生组织转化玉米具有实际意义。 还计划通过培养携带光合突变的植物来研究芽发育程序重置的分子性质，所述光合突变可以通过芽的正常发育过程而被抑制。 这些实验预计将提供洞察到正常的基因表达水平的变化，在连续的节点分化的一部分，植物的发展计划。

Switching from vegetative (indeterminate) to reproductive (determinate) growth is a major transition in the development of the shoot in higher plants. This transition occurs at the shoot apical meristem, the region that initiates primordia that differentiate as leaves separated by stem tissue during vegetative development or as floral organs during reproductive development. The timing of this transition has profound effects on the architecture of the shoot, as well as influencing yield in crop plants. The mechanism regulating the transition to flowering is beginning to be understood in plants in which the transition occurs in response to environmental cues. However, many other plants flower in a variety of environments. In these plants it is believed that the primary determinant of the timing of the transition from vegetative growth to flowering is a developmental program, of which little is known. The objective of the experiments proposed here is to examine various aspects of the developmental program underlying the switch to flowering in a plant of the latter group, maize. The meristem receives information from elsewhere in the plant and responds by either continuing leaf initiation (indeterminate) or becoming determined for determinate growth and forming an inflorescence, the tassel. This investigator will examine potential sources for that information by organ culture techniques. These experiments will lay the groundwork for the eventual identification of the signals that inform meristems of their progress through ontogeny, which results in the precise regulation of the morphology of maize shoots. The maize vegetative shoot apical meristem has been deduced to be organized in tiers, in which typically the lowermost cells (at the periphery) of the meristem will give rise to the first-formed nodes of the plant, midmeristem cells to the later nodes, and upper cells to the top of the plant. Cells most likely to participate in the formation of reproduct ive structures are located in the apex of the meristem. Resetting of the meristem by excision and culture results in more nodes being formed by the meristem than would normally occur. An inevitable result of this is a change in the contribution of at least some cells in the meristem to the shoot. This investigator will use clonal analysis to determine the origin within the meristem of the extra nodes of reset plants. This information will be useful for understanding the flexibility of cells within a meristem with respect to the portions of the plant to which they will contribute and the nature of the reorganization that takes place as a meristem is reset by excision and culture. This may also have practical implications for transformation of maize via the shoot meristem. Experiments are also planned to examine the molecular nature of the resetting of the shoot's developmental program by culturing plants carrying a photosynthetic mutation that can become suppressed through the course of normal development of a shoot. These experiments are expected to provide insight into normal changes at the level of gene expression in differentiation of successive nodes as part of the developmental program of the plant.