Manipulation of tomato root cells by Brg11, a TALE-like protein of the bacterial pathogen Ralstonia solanacearum

植物病原细菌将效应蛋白注入宿主细胞，宿主细胞操纵关键的细胞过程以促进疾病。因此，效应器可以作为分子探针来揭示植物与微生物相互作用的未知关键成分。我们研究了Brg11，这是一种效应蛋白，存在于许多广泛寄主的青枯病菌菌株中。Brg11在转录水平上激活了精氨酸脱羧酶(ADC)基因在所有寄主植物中的表达，这表明ADC蛋白促进了青枯病菌的毒力。ADC蛋白是多胺生物合成的限速酶，多胺是一类具有两个或更多氨基的代谢物，存在于所有三个生命王国中。青枯菌可以提高宿主PA水平，而细菌病原菌丁香假单胞菌则故意降低宿主PA水平。值得注意的是，PA水平的升高抑制了紫丁香的植物生长，但不抑制青枯病菌的生长。这些观察表明，青枯病菌Brg11诱导宿主细胞中PA水平升高，以抑制微生物生态位竞争对手的生长。我们将在细胞和分子水平上研究PA诱导的宿主细胞的变化。总体而言，这些研究将更好地了解植物PA水平如何影响宿主与微生物的相互作用。

Plant-pathogenic bacteria inject effector proteins into host cells that manipulate key cellular processes to promote disease. Thus, effectors can serve as molecular probes to uncover yet unknown key components of plant-microbe interactions. We study Brg11, an effector protein that is present in numerous strains of the broad-host pathogen Ralstonia solanacearum. Brg11 was found to transcriptionally activate expression of arginine decarboxylase (ADC) genes across all of its host plants, suggesting that ADC proteins promote virulence of R. solanacearum. ADC proteins are rate-limiting enzymes in the biosynthesis of polyamines (PAs), a class of metabolites with two or more amino groups that exist throughout all three kingdoms of life. While R. solanacearum was found to boost host PA levels, strains of the bacterial pathogen Pseudomonas syringae deliberately reduce host PA levels. Notably, elevated PA level inhibit in planta growth of P. syringae but not of R. solanacearum. These observations suggest that R. solanacearum Brg11 induces elevated PA levels in host cells to inhibit growth of microbial niche competitors. We will investigate PA-induced changes in host cells at the cellular and molecular level. Overall, these studies will provide a better understanding of how plant PA levels affect host-microbe interactions.