Regulation of in vitro morphogenesis

细胞如何在向器官或生物体生长的过程中获得特定的特征，是动植物发育生物学中一个基本但却知之甚少的问题。 植物的形态发生依赖于细胞改变其命运的能力，这一过程在地上部和根尖分生组织(SAM和RAMS)中得到了最好的例证。分生组织作为多能细胞的储存库，产生被招募来形成侧器官的衍生物。因此，多能细胞的自我更新和保留及其衍生细胞分化之间的平衡是分生组织功能的关键。植物球蛋白(PGBs)是一种清除一氧化氮(NO)的植物血红蛋白，影响细胞命运承诺 在胁迫条件下，通过延迟分化和保持分生组织细胞处于未分化状态来重新编程细胞命运。 这项研究计划包括两个主要目标。第一个目标将研究来自培养的拟南芥根的RAMs和SAM的个体发育以及PGBs(通过实验改变它们在培养细胞中的数量)在所分析的多潜能分生组织细胞的规格中的参与。PGB反应的中间产物，如一氧化氮、乙烯和细胞氧化还原状态的变化也将与SAM和RAM的形成有关。对根分生组织隔室的解剖，包括负责赋予多能性的静止细胞，也将被用来提高这些研究的分辨率。总而言之，这一目标的结果将提供一个在获得多能性过程中整合PGB行动和反应的模型。 第二个目标将确定通过从拟南芥体细胞组织中诱导胚性细胞来实现体细胞-胚性命运转变的机制。在这个体外系统中，胚性细胞是由WUSCHEL(WUS)的表达来定义的，抑制PGB会增加表达WUS的胚性细胞的数量。这项拟议的研究将集中在PGB如何通过研究细胞分裂素和生长素在体内分生组织细胞指定过程中的调节途径来调节WUS和胚胎细胞的指定。对新生胚性细胞和相邻体细胞的显微解剖和分离将确定决定体细胞-胚胎发生转变的因素。 该计划的创新之处在于利用和整合了大量的技术(结构、生理和分子)来测试所提出的控制细胞命运重定向的发育模型，以响应不断变化的培养条件。结果将是开创性的，因为它们不仅将促进胚胎发生领域，而且还将促进所有需要改变细胞行为的过程，这些过程对植物的繁殖、生产力和在不利条件下的生存至关重要。

How cells acquire specific characteristics as they grow towards an organ or organism is a fundamental and yet poorly understood question in animal and plant developmental biology. Plant morphogenesis relies on the ability of cells to redirect their fate, a process best exemplified in the shoot and root apical meristems (SAMs and RAMs). Meristems serve as a reservoir of pluripotent cells producing derivatives recruited for the formation of lateral organs. Balance between self-renewal and retention of pluripotent cells, and differentiation of their derivatives, is therefore key for meristem function. Phytoglobins (Pgbs), plant hemoglobins with nitric oxide (NO) scavenging properties, influence cell fate commitment and reprogram cell fate by delaying differentiation and maintaining meristematic cells in an undifferentiated state during conditions of stress. This program of research comprises two main objectives. The first objective will examine the ontogeny of RAMs and SAMs from cultured Arabidopsis roots and the participation of Pgbs (by experimentally altering their amount in cultured cells) in the specification of the pluripotent meristematic cells analysed. Intermediates of Pgb-responses, such as nitric oxide, ethylene and changes in cellular redox state will also be investigated in relation to SAM and RAM formation. Dissection of root meristem compartments, including the quiescent cells responsible for conferring pluripotency, will also be employed to increase the resolution of these studies. Collectively, results from this objective will provide a model integrating Pgb action and response during the acquisition of pluripotency. The second objective will define the mechanisms underlying the somatic-embryogenic fate transition by inducing embryogenic cells from Arabidopsis somatic tissue. In this in vitro system, embryogenic cells are defined by the expression of WUSCHEL (WUS), and suppression of Pgb increases the number of WUS-expressing embryogenic cells. The proposed research will focus on how Pgb regulates WUS and the specification of embryogenic cells by investigating cytokinin- and auxin-mediated pathways operating during meristematic cell specification in vivo. The microdissection and separation of nascent embryogenic cells from the adjacent somatic cells will identify factors determining the somatic-embryogenic transition. The novelty of this program resides in the utilization and integration of a large number of techniques (structural, physiological and molecular) to test proposed developmental models controlling the redirection of cell fate in response to changing culture conditions. Results will be ground breaking in that they will advance not only the field of embryogenesis, but also all those processes requiring a redirection of cell behavior which are crucial for plant propagation, productivity, and survival under adverse conditions.