Department of Plant Pathology, University of Wisconsin-Madison, U.S.A.
Analytical Instrumentation Center, School of Pharmacy, University of Wisconsin-Madison.
Mol Plant Microbe Interact. 2020 Mar;33(3):462-473. doi: 10.1094/MPMI-08-19-0218-R. Epub 2020 Jan 9.
The xylem-dwelling plant pathogen changes the chemical composition of host xylem sap during bacterial wilt disease. The disaccharide trehalose, implicated in stress tolerance across all kingdoms of life, is enriched in sap from -infected tomato plants. Trehalose in xylem sap could be synthesized by the bacterium, the plant, or both. To investigate the source and role of trehalose metabolism during wilt disease, we evaluated the effects of deleting the three trehalose synthesis pathways in the pathogen: TreYZ, TreS, and OtsAB, as well as its sole trehalase, TreA. A quadruple / mutant produced 30-fold less intracellular trehalose than the wild-type strain missing the trehalase enzyme. This trehalose-nonproducing mutant had reduced tolerance to osmotic stress, which the bacterium likely experiences in plant xylem vessels. Following naturalistic soil-soak inoculation of tomato plants, this triple mutant did not cause disease as well as wild-type . Further, the wild-type strain out-competed the trehalose-nonproducing mutant by over 600-fold when tomato plants were coinoculated with both strains, showing that trehalose biosynthesis helps overcome environmental stresses during infection. An (trehalose-6-phosphate synthase) single mutant behaved similarly to Δ in all experimental settings, suggesting that the OtsAB pathway is the dominant trehalose synthesis pathway in
木质部驻留植物病原体在细菌性萎蔫病期间改变宿主木质部汁液的化学成分。二糖海藻糖在所有生命领域的应激耐受中都有牵连，在感染的番茄植物汁液中丰富。木质部汁液中的海藻糖可能由细菌、植物或两者共同合成。为了研究萎蔫病中海藻糖代谢的来源和作用，我们评估了删除病原体中三种海藻糖合成途径（TreYZ、TreS 和 OtsAB）以及其唯一的海藻糖酶 TreA 的影响。与缺失海藻糖酶的野生型菌株相比，四重 / 突变体的细胞内海藻糖产量减少了 30 倍。这种不产生海藻糖的突变体对渗透压胁迫的耐受性降低，而细菌在植物木质部导管中可能会经历这种胁迫。在对番茄植物进行自然土壤浸泡接种后，这种三重突变体的发病情况不如野生型严重。此外，当番茄植物同时接种两种菌株时，野生型菌株的竞争优势超过 600 倍，表明海藻糖生物合成有助于在感染过程中克服环境压力。海藻糖-6-磷酸合酶（trehalose-6-phosphate synthase）的单突变体在所有实验设置中的表现与 Δ 相似，表明 OtsAB 途径是 中的主要海藻糖合成途径。
