Growing 'Up': Mechano-chemical aspects of anisotropic cell growth

成长“向上”：各向异性细胞生长的机械化学方面

• 批准号: BB/L002884/1
• 负责人: Siobhan Braybrook
• 金额: $ 48.11万
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2013
• 资助国家: 英国
• 起止时间: 2013 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FL002884%2F1
• 关键词: Growing; Up; Mechano; chemical; aspects

Human beings have become very skilled at building things; bridges, containers, houses, skyscrapers, auditoriums, cars, the list is endless. We can draw up a plan and manipulate materials to get most desired shapes and assemble those shapes into an object. However, this process is fundamentally different from how nature makes shapes, because nature grows things. A single cell can be multiplied, and its daughters altered in different ways, their subsequent growth rates and shapes changed, and those of their daughters, until a desired object is formed. Beyond even that, these shapes can be changed over time, responding to their environment and other cues, the ultimate smart-materials. We are only just beginning to understand the physical process of growth in plants, that is to say: what are the changes in the plant material that yield different shapes, and how are these changes regulated? To answer these questions, we will characterize a system involving a simple change in shape- the extension of a special organ, the hypocotyl, responsible for lifting the shoot tip out of the soil following germination.When a seed is planted in the soil, the young plant must extend itself out into the light and air to begin photosynthesis. This extension happens in a deceptively simple way: between the shoot tip and the root tip of a young plant there is a special organ- the hypocotyl. The hypocotyl has a fixed number of cells which begin as roughly cubed shapes, but who eventually increase in length over 200x, becoming very elongated rectangles, or cuboids. This type of growth is called anisotropic, where one direction of expansion exceeds the other; here length increase is greater than width. The result of anisotropic growth in the hypocotyl is the extension of the shoot tip up and out of the soil, very rapidly. An added bonus to the system is its dynamic response to light and gravity.What do we know about the control of cell growth direction in plants? A plant cell is basically a pressure filled box, where the pressure inside provides a non-directional force for growth and local changes in the wall provides the information about the direction of growth and hence any change in shape. The traditional view of anisotropic cell expansion, such as in the hypocotyl, is that each cell has a special organization in the wall, oriented cellulose fibers, that controls the direction of expansion. These fibers can be thought of as hoops around a barrel, limiting width expansion but capable of spreading apart to allow length increases. However, recent research points to a much more dynamic and complex picture. Within hypocotyl cells, cellulose orientation is more dynamic than previously thought- these are not just static hoops on barrels. In fact, true width-limiting orientations within the wall are only observed transiently after anisotropic expansion has begun, and even then not all the way around the cell surface, but only on their inner faces. Furthermore, another part of the cell wall, the pectin gel in which cellulose fibers are imbedded, is very important for regulating growth in plants.In this project we will characterize the biophysical and chemical changes in cell wall properties associated with anisotropic cell growth, and test the idea that these changes are coordinated by the plant hormone, auxin.

人类在建造事物方面已经变得非常熟练。桥梁、集装箱、房屋、摩天大楼、礼堂、汽车，这样的例子不胜枚举。我们可以制定计划并操纵材料以获得最想要的形状并将这些形状组装成一个物体。然而，这个过程与自然塑造形状的方式有着根本的不同，因为自然会生长事物。单个细胞可以繁殖，它的子细胞可以以不同的方式改变，它们随后的生长速度和形状也可以改变，它们的子细胞也可以改变，直到形成所需的物体。除此之外，这些形状可以随着时间的推移而改变，响应其环境和其他线索，这是终极智能材料。我们才刚刚开始了解植物生长的物理过程，也就是说：植物材料发生了哪些变化而产生了不同的形状，这些变化是如何调节的？为了回答这些问题，我们将描述一个涉及简单形状变化的系统 - 特殊器官（下胚轴）的延伸，负责在发芽后将芽尖从土壤中抬起。当种子种植在土壤中时，幼苗必须将自身延伸到阳光和空气中才能开始光合作用。这种延伸以一种看似简单的方式发生：在幼苗的茎尖和根尖之间有一个特殊的器官——下胚轴。下胚轴具有固定数量的细胞，最初为大致立方体形状，但最终长度增加超过 200 倍，变成非常拉长的矩形或长方体。这种类型的生长称为各向异性，其中一个方向的膨胀超过另一个方向；这里长度增加大于宽度。下胚轴各向异性生长的结果是芽尖非常迅速地向上延伸并伸出土壤。该系统的另一个好处是它对光和重力的动态响应。我们对植物细胞生长方向的控制了解多少？植物细胞基本上是一个充满压力的盒子，内部的压力为生长提供非方向性的力，细胞壁的局部变化提供了有关生长方向的信息，从而提供了形状变化的信息。各向异性细胞扩张（例如在下胚轴中）的传统观点是，每个细胞在壁上都有一个特殊的组织，即定向的纤维素纤维，控制着扩张的方向。这些纤维可以被认为是围绕桶的箍，限制宽度扩展，但能够散开以允许长度增加。然而，最近的研究指出了一幅更加动态和复杂的图景。在下胚轴细胞内，纤维素的定向比之前想象的更加动态——它们不仅仅是桶上的静态箍。事实上，壁内真正的宽度限制方向仅在各向异性膨胀开始后短暂地观察到，即使如此，也不是一直围绕细胞表面，而是仅在其内表面上观察到。此外，细胞壁的另一部分，即嵌入纤维素纤维的果胶凝胶，对于调节植物的生长非常重要。在这个项目中，我们将表征与各向异性细胞生长相关的细胞壁特性的生物物理和化学变化，并测试这些变化是由植物激素生长素协调的想法。

项目成果

How to let go: pectin and plant cell adhesion.

• DOI: 10.3389/fpls.2015.00523
• 发表时间: 2015
• 期刊: Frontiers in plant science
• 影响因子: 5.6
• 作者: Daher FB;Braybrook SA
• 通讯作者: Braybrook SA

Branched Pectic Galactan in Phloem-Sieve-Element Cell Walls: Implications for Cell Mechanics.

韧皮部筛元件细胞壁中的分支果胶半乳聚糖：对细胞力学的影响。

• DOI: 10.1104/pp.17.01568
• 发表时间: 2018
• 期刊: Plant physiology
• 影响因子: 7.4
• 作者: Torode,ThomasA;O'Neill,Rachel;Marcus,SusanE;Cornuault,Valérie;Pose,Sara;Lauder,RebeccaP;Kračun,StjepanK;Rydahl,MajaGro;Andersen,MathiasCF;Willats,WilliamGT;Braybrook,SiobhanA;Townsend,BelindaJ;Clausen,MadsH;Knox,JPa
• 通讯作者: Knox,JPa

Developmental Modulation of Root Cell Wall Architecture Confers Resistance to an Oomycete Pathogen.

• DOI: 10.1016/j.cub.2020.08.011
• 发表时间: 2020-11-02
• 期刊: Current biology : CB
• 作者: Gavrin A;Rey T;Torode TA;Toulotte J;Chatterjee A;Kaplan JL;Evangelisti E;Takagi H;Charoensawan V;Rengel D;Journet EP;Debellé F;de Carvalho-Niebel F;Terauchi R;Braybrook S;Schornack S
• 通讯作者: Schornack S