A dynamic rhizosphere interplay between tree roots and soil bacteria under drought stress
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Israel
Figures
Figure 1 with 2 supplements
Tree root recruitment of beneficial bacteria during drought and re-irrigation.
Bacterial dynamics in soil and rhizosphere around roots of irrigated and drought-exposed Cupressus sempervirens saplings. Root colonization (A): epifluorescence and bright-field images of drought …
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Figure 1—source data 1
Statistical analysis of bacterial growth.
- https://cdn.elifesciences.org/articles/79679/elife-79679-fig1-data1-v2.xlsx
Figure 1—figure supplement 1
Experimental system and climate.
(A) Each Cupressus sempervirens sapling was grown in a Rhizobox: a covered, transparent, container, allowing access to root sampling and exudates collection. (B) Diurnal changes in maximum (red) and …
Figure 1—figure supplement 2
Changes in soil water content (% v/v) in irrigated (blue) and drought-exposed (orange) saplings along the course of the experiment.
Vertical lines indicate the time points of specific interventions. Solid red and blue lines indicate irrigation cessation and re-irrigation, respectively. Dashed violet lines indicate the two …
Figure 2 with 1 supplement
Tree root exudates increase with bacterial inoculation for both the drought and irrigation treatments (A) and decrease with bacterial inoculation after rewetting the droughted trees (B).
Total organic carbon (TOC) in exudate solutions from roots of irrigated and drought-exposed Cupressus sempervirens saplings, with and without bacterial inoculations. Intact roots were incubated for …
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Figure 2—source data 1
Statistical analysis of gas exchange parameters and sapling biomass.
- https://cdn.elifesciences.org/articles/79679/elife-79679-fig2-data1-v2.xlsx
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Figure 2—source data 2
Statistical analysis of root exudates total organic carbon.
- https://cdn.elifesciences.org/articles/79679/elife-79679-fig2-data2-v2.xlsx
Figure 2—figure supplement 1
Drought stress effect on tree physiological parameters.
Leaf gas exchange dynamics of irrigated and drought-exposed Cupressus sempervirens saplings, with and without bacterial inoculations. Data points are means ± SE (n = 6) of (A) net assimilation; (B) …
Figure 3 with 1 supplement
Rhizosphere bacteria and drought induce systemic metabolic changes in root exudates.
Metabolic profiles of root exudate solutions from roots of irrigated and drought-exposed Cupressus sempervirens saplings, with and without bacterial inoculations. Intact roots were incubated for 48 …
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Figure 3—source data 1
Data and statistical analysis of root exudates polar metabolites.
- https://cdn.elifesciences.org/articles/79679/elife-79679-fig3-data1-v2.xlsx
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Figure 3—source data 2
Statistical analysis of root exudates semi-polar metabolites.
- https://cdn.elifesciences.org/articles/79679/elife-79679-fig3-data2-v2.xlsx
Figure 3—figure supplement 1
Semi-polar metabolic profiles of root exudate solutions from roots of irrigated and drought-exposed Cupressus sempervirens saplings, with and without bacterial inoculations.
Intact roots were incubated for 48 hr to collect exudates, which were analyzed by mass spectrometry. (A) Principal component analysis of the semi-polar metabolite profiles of exudates from exudates …
Figure 4 with 1 supplement
Specific metabolites in tree root exudates enhance bacterial growth.
Growth curves of Bacillus subtilis (left) and Pseudomonas stutzeri (right) in defined media with specific metabolites identified in root exudate blends of drought-exposed Cupressus sempervirens …
Figure 4—figure supplement 1
Growth curves of Bacillus subtilis (left) and Pseudomonas stutzeri (right) in defined media with specific metabolites identified in root exudate blends of drought-exposed Cupressus sempervirens saplings as exclusive carbon (A) or nitrogen (B) source.
Glycerol and monosodium glutamate (MSG) were used as controls for carbon and nitrogen sources, respectively. Root-derived metabolites are nicotinate, p-coumaric acid, and D-chiro-inositol. …
Figure 5
Leaf and soil elements respond to drought and bacterial inoculation.
Leaf elements (A) and soil phosphorous (B) of irrigated (blue shades) and drought-exposed and re-irrigated (brown shades) Cupressus sempervirens saplings, with and without bacterial inoculations. …
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Figure 5—source data 1
Statistical analysis of leaf elements.
- https://cdn.elifesciences.org/articles/79679/elife-79679-fig5-data1-v2.xlsx
Figure 6
Composite elemental distribution images of irrigated and drought-exposed leaves (A, B) and fine roots (C, D) of Cupressus sempervirens saplings.
Elemental distribution images (heat maps; a single color per element) were created at 20 µm resolution and scan area of 500 µm with a copper target to detect Fe, Mn, Ca, K, and Cl, and molybdenum or …
Figure 7
A dynamic rhizosphere interplay between tree roots and soil bacteria under drought stress.
Leaf CO2 assimilation distributed across the tree tissues (1). Under soil drought, leaf gas exchange and tree growth were inhibited (2). Trees recruited root-associated bacteria through changes in …
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Figure 7—source data 1
Statistical analysis of leaf assimilation, root exudation, and their relationships.
- https://cdn.elifesciences.org/articles/79679/elife-79679-fig7-data1-v2.pdf
Tables
Table 1
Dynamic changes in selected metabolites across treatments (DB, drought and bacterial inoculation; D, drought; I, irrigation) and along the experiment (drought and recovery following re-irrigation).
t-Test results are for pairwise comparisons between the relative changes of a metabolite between two treatments. Significant values are in boldface. Log 2 fold changes of the metabolites are for …
| Metabolite | t-Test | Log 2 fold change | ||||
|---|---|---|---|---|---|---|
| Drought DB/D | Drought D/I | Drought DB/D | Drought D/I | Re-irrigation DB/D | Re-irrigation D/I | |
| 2,3-Dihydroxybenzoate | 0.013 | 0.759 | 0.12 | 0.01 | –0.02 | –0.07 |
| 3,4-Dihydroxymandelate | 0.675 | 0.010 | –0.04 | 0.19 | 0.07 | 0.14 |
| 3,5-Dimethoxyphenol | 0.048 | 0.040 | –0.06 | 0.05 | 0.01 | 0.07 |
| Citrulline | 0.065 | 0.005 | 0.33 | –0.44 | –0.10 | 0.19 |
| N-acetylserine | 0.043 | 0.029 | 0.14 | –0.13 | –0.02 | 0.06 |
| D-chiro-inositol | 0.040 | 0.008 | 0.23 | –0.16 | –0.05 | 0.09 |
| Quinate | 0.025 | 0.014 | 0.26 | –0.25 | –0.08 | –0.14 |
| Nicotinate | 0.039 | 0.011 | 0.05 | –0.03 | 0.02 | 0.02 |
| p-Coumaric acid | 0.227 | 0.001 | 0.13 | –0.21 | –0.04 | 0.06 |
Table 2
Soil properties from pots where saplings were grown under treatments of drought or irrigated with or without bacteria.
| (A) Soil chemistry: pH, electrical conductivity (EC), sodium absorption ratio (SAR), and minerals content (Cl, Na, Ca, Mg, N-NH4, N-NO3, K concentrations) | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Soil | Treatment | pH | EC(ds m–1) | Cl(mg kg–1) | Na(g L–1) | Ca(mg kg–1) | Mg (mg kg–1) | SAR(mg kg–1) | N-NH4 (mg kg–1) | N-NO3 (mg kg–1) | K of CaCl2 (mg kg–1) |
| Pre (n=3) | Pre (n=3) | 7.5±0.06 | 1.88±0.07 | 87.7±3.0 | 54.4±3.6 | 750.7±8.8 | 11.8±0.3 | 2.8±0.09 | 18.9±3.0 | 25.63±3.4 | 49.43±3.9 |
| Drought | With bacteria | 7.5 | 2.51 | 170.0 | 179.4 | 1209.9 | 17.2 | 7.2 | 23.8 | 3.7 | 39.6 |
| Drought | W/o bacteria | 7.7 | 2.64 | 188.9 | 80.7 | 1222.4 | 16.9 | 3.2 | 19.1 | 3.5 | 37.3 |
| Irrigated | With bacteria | 7.6 | 6.31 | 513.6 | 54.4 | 3358.5 | 49.2 | 1.3 | 37.2 | 2.5 | 42 |
| Irrigated | W/o bacteria | 7.5 | 6.27 | 544.7 | 191.1 | 2716.3 | 51.1 | 5.1 | 41.9 | 3.6 | 39.6 |
| (B) Physical structure: sand, silt, and clay content, calcite content (CaCO3) and soil porosity (SP). | |||||||||||
| Soil | Treatment | Sand % | Salt % | Clay % | CaCO2 | SP | |||||
| Pre (n=3) | Pre (n=3) | 9±3.46 | 19.67±2.08 | 71.33±5.51 | 3.67±1.15 | 37.33±2.08 | |||||
