The cytokinins: signaling molecules within plants and among biota.

像动物一样，植物在发育过程中也使用激素。细胞分裂素是一类激素，由于其形式众多且浓度极低，因此使用起来具有挑战性。 20 多年来，我的实验室已经证明细胞分裂素可以增强种子的生长和农作物的产量。一路走来，有些事情我们无法仅用植物生理学来解释。很明显，细菌也产生细胞分裂素，并在某些情况下利用它们来控制植物生长。最奇怪的是，当我们继续观察时，我们发现我们研究的每种不同的生命形式也产生细胞分裂素。 真菌就是这种情况，我们也证明真菌可以产生细胞分裂素。最初，我们认为真菌产生细胞分裂素只是为了劫持植物的生长；后来我们发现，真菌制造细胞分裂素只是为了劫持植物的生长。但是，我们发现所有真菌都会产生细胞分裂素——即使是那些与植物无关的真菌。在本提案中，我们将了解细胞分裂素如何控制真菌本身的生长。为此，我们设计了一种真菌（玉米黑穗病），使其无法产生细胞分裂素。将这种突变真菌的生长与正常品种进行比较，看看这些细胞分裂素是否也可以充当真菌激素。此外，我们将使用该系统来确定致病性玉米黑穗病真菌和植物如何通过细胞分裂素的产生相互“交谈”，以协调肿瘤的产生。 在第二个项目中，我们将研究昆虫如何利用细胞分裂素的产生来引起植物肿瘤（虫瘿）。我们的早期结果表明，昆虫会产生细胞分裂素，无论它们是否会引起虫瘿。但产生虫瘿的细胞分裂素的数量和类型不同。这种差异可能是由于某些昆虫与产生细胞分裂素的细菌结合的能力造成的。我们将通过检查产瘿和不产瘿昆虫成虫和幼虫产生的细胞分裂素的数量和类型来检验这个想法。然后我们将确定用抗生素杀死昆虫体内的细菌是否会消除昆虫产生的任何细胞分裂素。 细胞分裂素活性在细菌、真菌、植物和昆虫中的普遍存在，引发了一个问题：它们在整个进化过程中在生物体中的作用是什么？为了回答这个问题，项目 3 将研究一种名为 Dictyostelium 的粘菌。在进化过程中，它处于植物、真菌和动物之间的结合点，可以深入了解细胞分裂素在不同王国中的共同或不同作用。在其不寻常的生命周期中，细胞可以单独存在，也可以组合形成多细胞生物。我们将研究细胞以这些不同方式组织时的细胞分裂素。将在盘基网柄菌生命周期中对细胞分裂素合成或代谢发生改变的野生型和突变株中的细胞分裂素进行分析。 总的来说，这组实验将揭示“植物”激素如何发挥作用，远远超出植物范围，影响其他几种生命形式。它将为理解生物体如何沟通提供基础，这可能对作物的生长方式以及它们如何抵抗真菌、细菌和害虫产生影响。

Like animals, plants use hormones in their development. The cytokinins, are a family of hormones, which are challenging to work with because of their numerous forms and extremely low concentrations. Over 20 years my lab has shown that cytokinins strengthen the growth of seeds and yield of crops. Along the way, there were things we couldn't explain just with plant physiology. It became apparent that bacteria also made cytokinins and, in some cases, used them to control plant growth. Most curiously, as we kept looking, we found that every different life form we studied, also produced cytokinins. This is the case with fungi, which we also showed can make cytokinins. Initially we believed fungi made cytokinin just to hijack the growth of plants; but, we discovered that all fungi make cytokinins - even those not associated with plants. In this proposal we will find out how cytokinins may control fungal growth itself. To do this, we engineered a fungus (corn smut) so that it can't make cytokinin. Growth of this mutant fungus will be compared to the normal variety to see if these cytokinins may also act as fungal hormones. Furthermore, we will use this system to determine how the pathogenic corn smut fungus and plants "talk" to each other, through cytokinin production, to orchestrate tumor production. In a second project, we will investigate how insects use cytokinin production to cause plant tumors (galls). Our early results indicate that insects make cytokinins regardless of whether they can cause galls; but the ones that make galls have different amounts and types of cytokinin. The difference may be caused by the ability of some insects to associate with cytokinin-producing bacteria. We will test this idea by examining the amounts and types of cytokinin made by gall producing and non-gall producing insect adults and larvae. We will then determine if killing bacteria in the insects with antibiotics will eliminate any of the cytokinin made by insects. The prevalence of cytokinin activity in bacteria, fungi, plants and insects, provokes a question - what is their role in organisms throughout evolution? To answer this, project 3 will work on a slime mold called Dictyostelium. In evolution it sits at a juncture between plants, fungi and animals and can provide insight into the common or diverging roles of cytokinin among kingdoms. In its unusual life cycle, cells can exist separately or assemble to form multicellular organisms. We will study cytokinins as cells organize in these different ways. Cytokinins will be analyzed during the Dictyostelium life cycle in wild-type and mutant strains with altered cytokinin synthesis or metabolism. Overall, these sets of experiments will reveal how "plant" hormones play roles well beyond plants to impact several other forms of life. It will provide a basis for understanding how organisms communicate, which can have impact for how crops grow and how they resist fungal, bacterial and insect pests.