RPG: Microbial Virulence Induction Enhancement by Plant CellWall Oligiosaccharides

这是一项针对女性的研究计划拨款。为了了解低聚糖在病原体和植物中的作用，从而控制植物疾病，破译生物间信号识别的细胞机制，我们将研究低聚糖对细菌毒力功能的增强作用。这种增强将作为一个模型系统，支持进一步追求真菌的毒力功能。先前的研究表明，植物细胞壁含有一种聚半乳糖醛酸酶抑制剂蛋白（PGIP），它可以识别和抑制真菌聚半乳糖醛酸酶（PG）， PG和PGIP的结合可以减少果胶的分解，从而形成3到20个单位长的低聚糖。这些低聚糖已被证明是植物细胞防御反应的诱导剂，在农杆菌中，类似的低聚糖已被认为是植物酚类物质诱导毒力的有效增强剂。本研究评估了梨和番茄PGIPs对细菌PGs的抑制作用，并确定了PGIP表达量升高的转基因番茄植株对农杆菌感染的敏感性。此外，还将鉴定可用于增强细菌毒力基因表达的低聚糖。本基金概述的研究结果将为在真菌中寻找负责诱导和增强毒力调节的细菌基因的同源物提供基础。为了能够理解在感染期间微生物病原体和植物细胞之间交换的信号，我们将分析糖聚合物对细菌功能的影响，使其能够感染植物细胞。已知这些糖聚合物是在植物细胞壁中的蛋白质PGIP遇到一种酶PG时形成的，真菌利用这种酶进入被感染的植物细胞内部。已知糖聚合物在植物细胞中引发反应，可以减缓感染过程，但它们也被认为可以增强细菌植物病原体的感染功能。由于对真菌感染植物所需的功能控制知之甚少，我们将首先描述糖聚合物在细菌病原体感染过程中的作用，然后在更复杂的真菌感染中寻找类似的功能。我们需要了解这两种类型的病原体和植物的功能，以便控制由这些病原体引起的植物疾病，并破译生物之间交流的基本机制。

This is a research planning grant for women. To be able to understand functions in pathogens and plants so that plant diseases can be controlled and cellular mechanisms for signal recognition between organisms can be deciphered, we will investigate enhancement of bacterial virulence functions by oligosaccharides. This enhancement will serve as a model system supporting further pursuit of virulence functions in fungi. Previous work has shown that plant cell walls contain a polygalacturonase inhibitor protein (PGIP) that recognizes and inhibits fungal polygalacturonases (PG) and that the association of PG and PGIP results in reduced breakdown of pectin so that oligosaccharides three to twenty units long are formed. These oligosaccharides have been shown to be inducers of defense responses in the plant cells and in Agrobacteria similar oligosaccharides have been suggested to be potent enhancers of virulence induction by plant phenolics. This research assesses the inhibition of bacterial PGs by pear and tomato PGIPs and determines the susceptibility to Agrobacteria infection of transgenic tomato plants expressing elevated amounts of PGIP. Furthermore, oligosaccharides optional for the enhancement of bacterialvirulence gene expression will be identified. The results from the studies outlined in this grant will provide the basis for the search in fungi for homologues to bacterial genes responsible for the regulation of virulence induction and enhancement. To be able to understand the signals that are exchanged between a microbial pathogen and a plant cell during infection, we will analyze the effect that sugar polymers have on the functions in a bacteria that allow it to infect the plant cells. These sugar polymers are known to be formed when a protein in the wall of the plant cell, PGIP, encounters an enzyme, PG, that fungi deploy in order to reach the interior of the plant cell being infected. The sugar polymers are known to trigger responses in plant cells that can slow the infection process, but they also have been suggested to enhance the infection functions in bacterial plant pathogens. Since little is known about the control of functions that fungal plant pathogenes need in order to infect plants, we will first describe the effects of the sugar polymers in the infection process by bacterial pathogens and then look for similar functions in the more complex fungal infections. We need to understand functions in both types of pathogens and in the plants in order to exercise control over plant diseases caused by these pathogens and in order to decipher basic mechanisms of communication between organisms.