Department of Microbiology and Immunology, The University of British Columbia, Vancouver, Canada.
Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, USA.
mBio. 2018 Nov 6;9(6):e00433-18. doi: 10.1128/mBio.00433-18.
and related plant root ("rhizosphere")-associated species contribute to plant health by modulating defenses and facilitating nutrient uptake. To identify bacterial fitness determinants in the rhizosphere of the model plant , we performed a high-throughput transposon sequencing (Tn-Seq) screen using the biocontrol and growth-promoting strain sp. WCS365. The screen, which was performed in parallel on wild-type and immunocompromised plants, identified 231 genes that increased fitness in the rhizosphere of wild-type plants. A subset of these genes decreased fitness in the rhizosphere of immunocompromised plants. We hypothesized that these genes might be involved in avoiding plant defenses and verified 7 sp. WCS365 candidate genes by generating clean deletions. We found that two of these deletion mutants, Δ (encoding a putative diguanylate cyclase/phosphodiesterase) and Δ (encoding a putrescine aminotransferase), formed enhanced biofilms and inhibited plant growth. We found that mutants and induced pattern-triggered immunity (PTI) as measured by induction of an PTI reporter and /dependent inhibition of plant growth. We show that MorA acts as a phosphodiesterase to inhibit biofilm formation, suggesting a possible role in biofilm dispersal. We found that both putrescine and its precursor arginine promote biofilm formation that is enhanced in the mutant, which cannot break down putrescine, suggesting that putrescine might serve as a signaling molecule in the rhizosphere. Collectively, this work identified novel bacterial factors required to evade plant defenses in the rhizosphere. While rhizosphere bacteria hold the potential to improve plant health and fitness, little is known about the bacterial genes required to evade host immunity. Using a model system consisting of and a beneficial sp. isolate, we identified bacterial genes required for both rhizosphere fitness and for evading host immune responses. This work advances our understanding of how evasion of host defenses contributes to survival in the rhizosphere.
并且相关的植物根际（“根际”）相关物种通过调节防御和促进养分吸收来促进植物健康。为了鉴定模式植物根际中的细菌适应性决定因素，我们使用生物防治和促生长菌株 sp. WCS365 进行了高通量转座子测序（Tn-Seq）筛选。该筛选在野生型和免疫缺陷型植物上平行进行，鉴定出了 231 个在野生型植物根际中增加适应性的基因。这些基因中有一部分降低了免疫缺陷型植物根际中的适应性。我们假设这些基因可能参与避免植物防御，并通过生成清洁缺失验证了 7 个 sp. WCS365 候选基因。我们发现这些缺失突变体中的两个，Δ（编码一个假定的二鸟苷酸环化酶/磷酸二酯酶）和 Δ（编码腐胺氨基转移酶），形成了增强的生物膜并抑制了植物生长。我们发现突变体和诱导了模式触发免疫（PTI），如通过诱导 PTI 报告基因和 /依赖的植物生长抑制来测量。我们表明 MorA 作为磷酸二酯酶起作用以抑制生物膜形成，这表明在生物膜分散中可能起作用。我们发现腐胺及其前体精氨酸都促进了生物膜的形成，而在不能分解腐胺的突变体中增强了生物膜的形成，这表明腐胺可能在根际中作为信号分子发挥作用。总的来说，这项工作鉴定了在根际中逃避植物防御所需的新的细菌因子。虽然根际细菌有可能改善植物健康和适应性，但对于逃避宿主免疫所需的细菌基因知之甚少。使用由 sp. 和有益的分离株组成的模型系统，我们鉴定了既适应根际又逃避宿主免疫反应的细菌基因。这项工作增进了我们对逃避宿主防御如何有助于在根际中生存的理解。
