Effects of Jasmonic Acid, Ethylene, and Salicylic Acid Signaling on the Rhizosphere Bacterial Community of Arabidopsis thaliana

Plant-Microbe Interactions, Institute of Environmental Biology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
Molecular Plant-Microbe Interactions (Impact Factor: 3.94). 04/2011; 24(4):395-407. DOI: 10.1094/MPMI-05-10-0115
Source: PubMed


Systemically induced resistance is a promising strategy to control plant diseases, as it affects numerous pathogens. However, since induced resistance reduces one or both growth and activity of plant pathogens, the indigenous microflora may also be affected by an enhanced defensive state of the plant. The aim of this study was to elucidate how much the bacterial rhizosphere microflora of Arabidopsis is affected by induced systemic resistance (ISR) or systemic acquired resistance (SAR). Therefore, the bacterial microflora of wild-type plants and plants affected in their defense signaling was compared. Additionally, ISR was induced by application of methyl jasmonate and SAR by treatment with salicylic acid or benzothiadiazole. As a comparative model, we also used wild type and ethylene-insensitive tobacco. Some of the Arabidopsis genotypes affected in defense signaling showed altered numbers of culturable bacteria in their rhizospheres; however, effects were dependent on soil type. Effects of plant genotype on rhizosphere bacterial community structure could not be related to plant defense because chemical activation of ISR or SAR had no significant effects on density and structure of the rhizosphere bacterial community. These findings support the notion that control of plant diseases by elicitation of systemic resistance will not significantly affect the resident soil bacterial microflora.

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    • "Hence, there is evidence that during the early stages of colonization both arbuscular mycorrhizal (AM) and Rhizobium species locally suppress SA signaling (García-Garrido and Ocampo, 2002; Stacey et al., 2006), suggesting that defense phytohormones normally act to inhibit microbial survival in the root. Indeed, culture-dependent studies in A. thaliana have demonstrated a significantly lower load of culturable bacteria in rhizospheres of plants with either defective JA signaling or, conversely, constitutive SA production (Doornbos et al., 2011). Beyond defense phytohormones, other immune outputs have also been implicated by recent studies. "
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    • "A rhizosphere community may be altered by changes in root exudate composition leads the changes in nutritional status. On other hand, Doornbos et al. (2011) concerned over the effects of plant genotype on rhizosphere bacterial community structure and found no relationship to plant defense because chemical activation of induced systemic resistance (ISR) or systemic acquired resistance (SAR) had no significant effects on density and structure of the rhizospheric community resultant none effect on the resident soil bacteria. Most common bacteria in the ecology of rhizosphere includes Actinoplanes, Agrobacterium , Alcaligens, Amorphosporangium, Arthrobacter, Azospirillum, Azotobacter, Bacillus, Paenibacillus, Burkholderia, Cellulomonas, Enterobacter, Erwinia, Flavobacterium, Gluconacetobacter, Microbacterium, Micromonospora, Pseudomonas , Rhodopseudomonas, Rhizobia, Serratia, Streptomyces, Xanthomonas, etc., as stated by several workers (Kloepper et al. 1989; Tang 1994; Okon and Labandera-Gonzalez 1994; Glick et al. 1999; Mayak et al. 2001; Tahmatsidou et al. 2006; Aslantas et al. 2007; Lee et al. 2008; Pedraza et al. 2010). "
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    • "studies. Further, although culture-dependent and -independent studies do not show a consistent impact of JA signaling on phyllosphere or root microbiome composition (Kniskern et al., 2007; Doornbos et al., 2011; Santhanam et al., 2014), recent massive parallel sequencing studies identified ethylene signaling contributions to A. thaliana phyllosphere microbiome composition (Bodenhausen et al., 2014). Together, these results represent the start of controlled experiments taking advantage of isogenic mutants in A. thaliana to understand how phytohormones might impact the composition of plant-associated microbial communities. "
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