RUI: Control of Branching in Neurospora Crassa

与大多数丝状真菌一样，粗糙脉孢菌的生长始于高度极化的细胞伸展，导致形成直径均匀的菌丝管。不断延伸的尖端发出周期性的分支，这些分支本身就能够伸展和分支。很少有其他生物系统以这种方式发展。新的分枝通常出现在延伸顶端的后面很短的距离处，并与主菌丝成一定角度生长，被称为“侧枝”。在正常情况下，大多数分支点是横向形成的，但在少数分支点上可以看到交替的分支形态。在这种少数形态中，两个尖端与先前的生长方向成一定角度，形成分叉结构。这些分支点被称为‘二分’或‘尖端’分支点。在这个项目中，将研究控制枝条形态的遗传学。该项目将侧重于在粗糙脉孢菌中观察到的侧向/二分型二型性。该项目预计将沿着两条独立的战线推进。首先，将通过筛选一组已知形态突变的抑制子来扩大形态突变的集合。在该项目的这一阶段，重点将放在导致有利于二叉分支的突变上。预计这将发现作用于特定分枝突变体的抑制子，并有望恢复那些至少能够部分抑制对更广泛的形态突变的分枝效应的抑制子，实际上，作为低分枝突变体。在脉孢菌属中，这种突变在很大程度上是未知的。其次，将进一步研究冷休克的形态效应。在脉孢子虫中，温度变化(25到4℃)已经被证明引起了戏剧性的但暂时的分枝效应。响应的一个阶段的特征是在形态上切换到所有的二叉分支。通过筛选对冷休克反应发生改变的突变体，应该确定与枝条形态之间的发育转换有关的基因。丝状真菌在人类事务中发挥着重要作用。它们是生物质的主要回收者，也是农业和木材生产损失的重要来源，因为它们是病原体和腐败剂。它们影响生产者(产品损失、抗真菌行动的成本)和消费者(成本增加、食品变质、木制品分解)，因此具有重大的经济影响。增加我们对真菌顶端生长和分枝的了解，将有助于更直接地控制有机体的生长。该项目将被证明对批量培养技术、控制受温度变化影响的材料中的真菌有用，并应扩大我们对丝状真菌在该领域中生长的理解。

0233242WattersAs in most filamentous fungi, growth of Neurospora crassa begins by highly polarized cell extension that leads to the formation of a hyphal tube of uniform diameter. The continuously extending tip sends off periodic branches, which are themselves, capable of extension and branching. There are few other biological systems that develop in this manner. New branches normally emerge a short distance behind the apex of the extending tip and grow at an angle to the main hypha and are referred to as 'lateral' branches. Under normal conditions the majority of branch points form laterally, but alternate branch morphology is seen at a minority of branch points. In this minority morphology, the two tips emerge at an angle to the previous direction of growth forming a forked structure. These are referred to as 'dichotomous' or 'apical' branch points. In this project, the genetics of control of branch morphology will be examined. The project will focus on the lateral/dichotomous dimorphism observed in Neurospora crassa. The project is expected to advance along two independent fronts. First, the collection of morphological mutations will be expanded by screening for suppressors of a select group of known morphological mutations. In this phase of the project, the focus will be on mutations that cause a shift in favor of dichotomous branching. This is expected to uncover suppressors which act on specific branching mutants, and hopefully will also recover those which are capable of at least partially suppressing the branching effect on a wider selection of morphological mutations, acting, in effect, as low-branching mutants. Such mutations are largely unknown in Neurospora. Second, the morphological effects of cold shock will be further examined. In Neurospora, temperature shifts (25 to 4) have been shown to cause a dramatic, but temporary branching effect. One phase of the response is characterized by a switch in morphology to all dichotomous branching. By screening for mutants with altered responses to cold shock, genes responsible for the developmental switch between branch morphologies should be identified.Filamentous fungi play a large role in human affairs. They are major recyclers of biomass and a significant source of losses in agriculture and lumber production as pathogens and agents of spoilage. They affect both producers (loss of product, cost of antifungal actions) and consumers (increased costs, food spoilage, decomposition of wood products) and thus have a significant economic impact. An increase in our understanding of tip growth and branching in fungi would prove useful for more direct control of the growth of the organism. The project should prove useful to batch culturing technologies, control of fungi in material subjected to temperature shifts, and should expand our understanding of the growth of filamentous fungi in the field.