In-Situ Metabolomic Analysis of Setaria viridis Roots Colonized by Beneficial Endophytic Bacteria

Journal Article · 06 December 2019 · Molecular Plant-Microbe Interactions

DOI: https://doi.org/10.1094/MPMI-06-19-0174-R · OSTI ID:1602752

Agtuca, Beverly J.  ^[1]; Stopka, Sylwia A. ^[2]; Tuleski, Thalita R.  ^[3]; do Amaral, Fernanda P. ^[1]; Evans, Sterling ^[1]; Liu, Yang ^[1]; Xu, Dong ^[1]; Monteiro, Rose Adele ^[4]; Koppenaal, David W. ^[5]; Paša-Tolić, Ljiljana ^[5]; Anderton, Christopher R. ^[5]; Vertes, Akos ^[2]; Stacey, Gary  ^[1]

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1. Univ. of Missouri, Columbia, MO (United States)
2. George Washington Univ., Washington, DC (United States)
3. Univ. of Missouri, Columbia, MO (United States); Federal Univ. of Paraná, Curitiba (Brazil)
4. Federal Univ. of Paraná, Curitiba (Brazil)
5. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)

Over the past decades, crop yields have risen in parallel with increasing use of fossil-fuel derived nitrogen (N) fertilizers, but with concomitant negative impacts on climate and water resources. There is a need for more sustainable agricultural practices, and biological nitrogen fixation (BNF) could be part of the solution. A variety of nitrogen-fixing, epiphytic and endophytic plant growth promoting bacteria (PGPB) are known to stimulate plant growth. However, compared to the rhizobium-legume symbiosis, little mechanistic information is available as to how PGPB affect plant metabolism. Therefore, we investigated the metabolic changes in roots of the model grass species Setaria viridis upon endophytic colonization by Herbaspirillum seropedicae SmR1 (fix⁺) or a fix^- mutant strain (SmR54), compared to uninoculated roots. Endophytic colonization of the root is highly localized and, hence, analysis of whole root segments dilutes the metabolic signature of those few cells impacted by the bacteria. Therefore, we utilized in situ laser ablation electrospray ionization mass spectrometry (LAESI-MS) to sample only those root segments at or adjacent to the sites of bacterial colonization. We report netabolites involved in purine, zeatin, and riboflavin pathways were significantly more abundant in inoculated plants while metabolites indicative of nitrogen, starch, and sucrose metabolism were reduced in roots inoculated with the fix^- strain or uninoculated, presumably due to N limitation. Interestingly, compounds, involved in indole-alkaloid biosynthesis were more abundant in the roots colonized by the fix^- strain, perhaps reflecting a plant defense response.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: AC05-76RL01830
• OSTI ID: 1602752
• Report Number(s): PNNL-SA-145863
• Journal Information: Molecular Plant-Microbe Interactions, Vol. 33, Issue 2; ISSN 0894-0282
• Publisher: APS Press - International Society for Molecular Plant-Microbe InteractionsCopyright Statement
• Country of Publication: United States
• Language: English