Abstract
Plant-microbe associations are thought to be beneficial for plant growth and resistance against biotic or abiotic stresses, but for natural ecosystems, the ecological analysis of microbiome function remains in its infancy. We used transformed wild tobacco plants (Nicotiana attenuata) which constitutively express an antimicrobial peptide (Mc-AMP1) of the common ice plant, to establish an ecological tool for plant-microbe studies in the field. Transgenic plants showed in planta activity against plant-beneficial bacteria and were phenotyped within the plants´ natural habitat regarding growth, fitness and the resistance against herbivores. Multiple field experiments, conducted over 3 years, indicated no differences compared to isogenic controls. Pyrosequencing analysis of the root-associated microbial communities showed no major alterations but marginal effects at the genus level. Experimental infiltrations revealed a high heterogeneity in peptide tolerance among native isolates and suggests that the diversity of natural microbial communities can be a major obstacle for microbiome manipulations in nature.
Highlights
Plants are surrounded by a vast and diverse community of soil bacteria, some of which are able to form close associations and important mutualistic relationships with plants (Hardoim et al, 2015; Müller et al, 2016)
We show that the seed specific peptide Mc-AMP1 from the common ice plant can be ectopically expressed in N. attenuata plants without altering morphology or growth performance of the transgenic plants
Despite the concerns that an unwary expression of Antimicrobial peptides (AMPs) for crop disease resistance engineering might disturb the native microbial flora, with unexpected ecological consequences for the plant, we found no evidence for growth or fitness related aberrations of AMP expression
Summary
Plants are surrounded by a vast and diverse community of soil bacteria, some of which are able to form close associations and important mutualistic relationships with plants (Hardoim et al, 2015; Müller et al, 2016). Most microbiota inhabit plants without producing symptoms, and despite the assumption of evolutional benefits of the plant’s holobiont, little is known about the ecological relevance of most plant-associated bacteria (Müller et al, 2016; Sánchez-Cañizares et al, 2017). Functional characterizations are usually limited to culturable bacteria, frequently used in gnotobiotic conditions or inoculated in titers higher than those of native soils and likely overestimating their real roles in nature (Haney et al, 2015). The reconstruction and establishment of artificial communities or microbial consortia refines this approach, but remains restricted to culturable bacteria (Vorholt et al, 2017)
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