Rhizosphere bacterial sulfatases and their control by interactions with plants

植物需要硫来生长，但农业土壤中的大部分硫以结合形式（“硫酸酯”）存在，可以被一些细菌使用，但不能直接被植物使用。这些细菌中的许多与植物根部密切相关，在根部本身及其周围的土壤（“根际”）中形成密集的群落。它们被植物积极滋养，植物利用光合作用产生糖和氨基酸，这些糖和氨基酸从根部释放出来促进细菌生长，作为回报，许多这些与根部相关的细菌通过从土壤中动员矿物质营养素（包括硫）来促进植物生长。这种相互作用依赖于植物和微生物之间的通信网络，由专门的细菌群体负责土壤中的某些功能，植物使用特定的信号刺激这些细菌产生所需的营养物质。本项目将研究根际硫代谢的两个主要方面。首先，我们将研究哪些细菌家族在促进土壤中结合硫的释放以供植物使用方面是重要的。由于许多土壤细菌不能在实验室中培养，我们将从建立一个数据库的硫酸酯利用基因从可培养的土壤细菌，可以代谢硫酸酯。然后，我们将使用这个数据库来调查在英国种植的三种最重要的农作物，小麦，大麦和油菜根际的整体微生物群落。这将提供重要的新信息，以确定最重要的细菌物种的硫酸酯代谢在我们的主要作物的根际。为了提高这些数据的预测能力，我们将在这些作物的最具商业重要性的品种的根际，在英国从彭赞斯到阿伯丁的田间试验现场验证这些发现。在确定了在土壤硫酸酯代谢中最活跃的细菌之后，下一步是描述植物如何控制它们的活性。我们的初步研究结果表明，植物可以促进硫酸酯代谢最重要的细菌酶芳基硫酸酯酶的产生，并且一旦产生也可以刺激其活性。这两个过程发生的机制将在一系列的植物，包括作物和其他物种，通过分离的拟南芥蛋白，负责刺激芳基硫酸酯酶的活性，并采取第一步，阐明植物根分泌物如何可以推翻正常的细菌控制芳基硫酸酯酶的生产。这些结果将为植物如何控制根际环境中的养分循环提供新的见解，并可能在促进英国可持续农业方面发挥作用。

Plants require sulfur for growth, but much of the sulfur in agricultural soils is present in a bound form ('sulfate esters') that can be used by some bacteria, but not directly by plants. Many of these bacteria live in close association with plant roots, forming dense communities on the root itself and in the soil immediately surrounding it (the 'rhizosphere'). They are actively nourished by the plant, which uses photosynthesis to produce sugars and amino acids that are released from the root to promote bacterial growth, and in return many of these root-associated bacteria promote plant growth by mobilizing mineral nutrients (including sulfur) from the soil for plant utilization. This interaction relies on a network of communication between plants and microbes, with specialist groups of bacteria responsible for certain functions in the soil, and the plant using specific signals to stimulate these bacteria to produce the nutrients it needs. This project will examine two main aspects of sulfur metabolism in the rhizosphere. First, we will investigate which bacterial families are important in promoting the release of bound sulfur from the soil for plants to use. Because many soil bacteria cannot be cultivated in the laboratory, we will start by establishing a database of sulfate ester utilization genes from cultivable soil bacteria that can metabolize sulfate esters. We will then use this database to investigate the overall microbial community in the rhizosphere of the three most important agricultural crops that are grown in the United Kingdom, wheat, barley and oilseed rape. This will provide vital new information to identify the most important bacterial species for sulfate ester metabolism in the rhizosphere of our major crops. To increase the predictive power of this data we will then validate these findings in the rhizospheres of the most commercially important cultivars of these crops, on field trial sites across the UK from Penzance to Aberdeen. Having identified the bacteria that are most active in soil sulfate ester metabolism, the next step is to characterize how plants control their activity. Our preliminary findings show that plants can promote the production of the most important bacterial enzyme for sulfate ester metabolism, arylsulfatase, and can also stimulate its activity once produced. The mechanisms by which these two processes occur will be investigated in a range of plants, including both crops and other species, by isolating the Arabidopsis protein that is responsible for stimulating arylsulfatase activity, and taking the first steps in elucidating how plant root exudates can override the normal bacterial control of arylsulfatase production. The results will provide new insights into how plants control nutrient cycling in the rhizosphere environment, with potential applications in promoting sustainable agriculture in the United Kingdom.