Defense hormones modulate root microbiome diversity and composition in tomato

Abstract

Plant roots live closely associated with soil microbes. Understanding how roots defend against pathogenic microbes while associating with non-pathogenic microbes is critical to using root microbiomes for successful outcomes. The aim of this study was to determine the contribution of the plant defense hormones ethylene (ET), jasmonic acid (JA), and salicylic acid (SA) to the tomato root microbiome. We used 16S rRNA amplicon sequencing to examine the root microbiome of four tomato genotypes defective in three hormone pathways. We found that ET and SA pathways, but not JA, were critical for root endosphere microbial alpha (α)-diversity. Root endosphere communities of ACD, deficient in a precursor of ET, and the SA-deficient NahG transgenic, had significantly less α-diversity than wild-type tomatoes. NahG and ACD root endosphere enrichment profiles were similar and driven by two taxa. In NahG, ACD, and in a panel of 24 wild-type tomatoes, the abundance of these two taxa was correlated with lower root endosphere α-diversity. The abundance of these taxa was also moderately negatively correlated with the level of SA in roots. Our results suggest that SA and ET pathways contribute to tomato root endosphere diversity by modulating the abundance of specific bacterial taxa.

Combination of Bacillus and Low Fertigation Input Promoted the Growth and Productivity of Chinese Cabbage and Enriched Beneficial Rhizosphere Bacteria Lechevalieria

“…A previous study has shown that PGPBs can activate induced systemic resistance via salicylic acid- or jasmonic acid (and ethylene)-dependent signaling pathways to improve plant resistance against drought or salinity [ 84 ]. The distinction might be ascribed to the level of drought stress inducing different hormones and exudates in cabbage roots that reshape the bacterial communities [ 85 ]. Correlation analysis showed that the contents of indole-3-acetic acid and salicylic acid were related to the abundance of some actinomycetes in the rhizosphere under low-fertigation conditions, but the correlation was insignificant ( Figure 6 C).…”

Microbiome-Mediated Strategies to Manage Major Soil-Borne Diseases of Tomato

“…Endosphere communities of tomato associated with degradation of the ET precursor 1-aminocyclopropane-1-carboxylic acid (ACC). [166,167] Cytokinin (CK)…”

Hormones as go‐betweens in plant microbiome assembly

“…In fact, the taxonomic profile at‐large of bacterial endosphere communities appears to be strongly driven by SA accumulation/insensitivity, as revealed by several immune signalling mutant genotypes (Lebeis et al ., 2015 ). Similarly, endosphere communities of tomato ( Solanum lycopersicum ) plants constitutively degrading the ET precursor 1‐aminocyclopropane‐1‐carboxylic acid (ACC) showed a reduced alpha diversity compared to wild‐type plants (French et al ., 2019 ).…”

“…These mutants maintain their ability to synthesise SA and in fact may have elevated levels of SA under some conditions (Rayapuram and Baldwin, 2007 ). The SA‐associated alpha diversity reduction that was observed in root endospheres extended into the rhizosphere (Hein et al ., 2008 ; Doornbos et al ., 2011 ) while constitutive degradation of SA reduced alpha diversity in the endosphere but not rhizosphere of tomato or Arabidopsis (Doornbos et al ., 2011 ; French et al ., 2019 ). Moreover, direct SA application affected microbes in bulk soil indicating SA plant signalling‐independent effects on microbial communities (Lebeis et al ., 2015 ).…”