Piecing Together the Agrobacterium Type IV Secretion System Involved In DNA Transfer to Plants

农杆菌是一种土壤细菌，具有将DNA从细菌转移到植物细胞中的天然能力，并在植物细胞中整合到植物基因组中。科学家们利用这种能力，利用感兴趣的DNA对植物进行基因工程。虽然已经阐明了转变途径中的许多步骤，但仍然存在一个主要问题。DNA是如何从细菌中转运到植物中的？农杆菌DNA转运体属于一类进化上保守的转运体，称为IV型分泌系统（T4SS）。T4SS参与i)细菌交配，ii)致病菌感染植物和动物宿主时蛋白质毒素的输出。农杆菌T4SS含有12种蛋白；长期目标是了解这12种蛋白质如何建立T4SS结构和功能。这项研究将首先确定哪些蛋白质相互作用，从而密切接触。这种方法定义了哪些蛋白质对位于通道的入口，而不是通道的外部或内部，并导致t4ss装置组装的模型。其次，遗传策略将证实这些预测模型。最后，该研究将利用晶体学和生物信息学确定单个T4SS蛋白的3D结构。因此，这些研究将为T4SS提供一个确切的结构。这项基础研究将在医学和农业方面影响社会。关于T4SS的结构信息对于开发疾病治疗方法至关重要，这些治疗方法可以破坏将毒素转移到易感宿主的细菌中的转运蛋白功能。此外，对T4SS的理解可能允许对农杆菌中的转运体进行修饰，以提高其对植物转化的有效性。

Agrobacterium is a soil bacterium with the natural ability to transfer DNA from the bacterium into the plant cell where it integrates into the plant's genome. Scientists co-opt this ability, allowing the genetic engineering of plants, with DNA of interest. While many steps in the transformation pathway have been elucidated, a major question remains. How is DNA transported out of the bacterium and into the plant? The Agrobacterium DNA transporter belongs to a growing class of evolutionarily conserved transporters, called type IV secretion systems (T4SS). T4SS are involved in i) bacterial mating, and ii) protein toxin export when pathogenic bacteria infect plant and animal hosts. The Agrobacterium T4SS contains 12 proteins; the long-term goal is to understand how these 12 proteins establish T4SS architecture and function. The research will first determine which proteins interact with each other, and thus are in close contact. This approach defines which pairs of proteins reside at the entrance, versus the exterior or interior of the channel, and leads to models for the assembly of theT4SS apparatus. Second, genetic strategies will confirm these predicted models. Finally, the research will determine the 3D structure of individual T4SS proteins using crystallography and bioinformatics. Thus, these studies will provide an exact structure for the T4SS. This basic research will impact society in medicine and agriculture. Structural information on the T4SS is essential to allow the development of disease treatment therapies that disrupt transporter function in bacteria that transfer toxins to susceptible hosts. Moreover, an understanding of T4SS may allow modification of the transporter in Agrobacterium to increase its effectiveness for plant transformation.