The pervasive impact of cytokinins: signaling within plants and among biota.

像动物一样，植物利用激素来协调其器官的发育和组装，如根、枝、叶、茎节、花和果实。一组激素，被称为细胞分裂素，是一个由大约25-30种相关化合物组成的家族，由于它们的形式众多，而且它们的作用浓度极低，因此处理这些化合物非常具有挑战性。由于它们可能对种子生长产生强有力的影响，它们是提高作物产量的有力候选。为了帮助评估这种潜力，我们将看到细胞分裂素是如何帮助短柄草种子形成和发育的，短柄草是一种与燕麦和小麦等谷物相关的遗传模式植物。这将通过工程基因来完成，这些基因负责在年轻的种子中制造、降解或激活细胞分裂素。转基因种子的细胞分裂素活性是高于还是低于正常水平，这将揭示细胞分裂素是促进还是抑制种子生长，以及可能的产量。奇怪的是，我们的实验室发现真菌可以制造植物激素，包括细胞分裂素。虽然它们制造细胞分裂素是为了劫持植物的生长，但我们发现，即使是与植物无关的真菌，也会制造细胞分裂素。为了找出它们是如何影响真菌生长本身的，我们对一种真菌（玉米黑穗病）进行了基因工程改造，使其不再产生细胞分裂素。将这种突变真菌的生长特征与正常品种进行比较，看看这些细胞分裂素是否也可能是真菌激素。最后，我们将研究昆虫如何利用细胞分裂素的产生引起植物肿瘤（胆囊）。我们的早期研究结果表明，昆虫产生细胞分裂素，不管它们是否会引起胆囊；但是产生胆汁的细胞分裂素的数量和类型不同。事实上，这种差异可能是由一些昆虫与细菌结合的能力引起的，细菌也能产生几种类型的细胞分裂素。我们将通过检查产瘿昆虫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。此外，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。这些实验将揭示“植物”激素如何影响远远超出植物的许多其他形式的生命。

Like animals, plants use hormones to orchestrate development and assembly of their organs like: roots, branches, leaves, stem nodes, flowers and fruits. One group of hormones, known as the cytokinins, is a family of about 25-30 related compounds, which are are very challenging to work with because of the numerous forms and extremely low concentrations at which they operate. Because of their possible potent influence over seed growth they are strong candidates for increasing crop yield. To help evaluate this potential, we will see how cytokinins help seeds form and develop in Brachypodium, a genetic model plant related to cereals like oats and wheat. This will be done by engineering genes that are responsible for making, degrading or activating cytokinins in young seeds. The transgenic seeds have either higher or lower than normal cytokinin activity and will reveal whether cytokinins promote or inhibit seed growth, and possibly yield. Curiously our lab has found that fungi can make plant hormones, including the cytokinins. Although they make them to hijack the growth of plants, we discovered that even fungi, not associated with plants, make cytokinins. To find out how they might affect fungal growth itself, we have genetically engineered a fungus (corn smut) so that it can no longer make cytokinin. Growth characteristics of this mutant fungus will be compared to the normal variety to see if these cytokinins may also be fungal hormones. Lastly 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 in fact be caused by the ability of some insects to associate with bacteria which also make several types of cytokinins. 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. Furthermore we will determine if killing bacteria in the insects with anitbiotics will eliminate any of the cytokinin made by insects. These sets of experiments will reveal how "plant" hormones impact well beyond plants to influence many other forms of life.