Search

Background: Potato seed tubers are colonized and inhabited by soil-borne microbes, that can affect the performance of the emerging daughter plant in the next season. In this study, we investigated the intergenerational inheritance of microbiota from seed tubers to next-season daughter plants under field condition by amplicon sequencing of bacterial and fungal microbiota associated with tubers and roots, and tracked the microbial transmission from different seed tuber compartments to sprouts. Results: We observed that field of production and potato genotype significantly (P < 0.01) affected the composition of the seed tuber microbiome and that these differences persisted during winter storage of the seed tubers. Remarkably, when seed tubers from different production fields were planted in a single trial field, the microbiomes of daughter tubers and roots of the emerging plants could still be distinguished (P < 0.01) according to the production field of the seed tuber. Surprisingly, we found little vertical inheritance of field-unique microbes from the seed tuber to the daughter tubers and roots, constituting less than 0.2% of their respective microbial communities. However, under controlled conditions, around 98% of the sprout microbiome was found to originate from the seed tuber and had retained their field-specific patterns. Conclusions: The field of production shapes the microbiome of seed tubers, emerging potato plants and even the microbiome of newly formed daughter tubers. Different compartments of seed tubers harbor distinct microbiomes. Both bacteria and fungi on seed tubers have the potential of being vertically transmitted to the sprouts, and the sprout subsequently promotes proliferation of a select number of microbes from the seed tuber. Recognizing the role of plant microbiomes in plant health, the initial microbiome of seed tubers specifically or planting materials in general is an overlooked trait. Elucidating the relative importance of the in

Despite the numerous benefits plants receive from probiotics, maintaining consistent results across applications is still a challenge. Cultivationindependent methods associated with reduced sequencing costs have considerably improved the overall understanding of microbial ecology in the plant environment. As a result, now, it is possible to engineer a consortium of microbes aiming for improved plant health. Such synthetic microbial communities (SynComs) contain carefully chosen microbial species to produce the desired microbiome function. Microbial biofilm formation, production of secondary metabolites, and ability to induce plant resistance are some of the microbial traits to consider when designing SynComs. Plant-associated microbial communities are not assembled randomly. Ecological theories suggest that these communities have a defined phylogenetic organization structured by general community assembly rules. Using machine learning, we can study these rules and target microbial functions that generate desired plant phenotypes. Well-structured assemblages are more likely to lead to a stable SynCom that thrives under environmental stressors as compared with the classical selection of single microbial activities or taxonomy. However, ensuring microbial colonization and long-term plant phenotype stability is still one of the challenges to overcome with SynComs, as the synthetic community may change over time with microbial horizontal gene transfer and retainedmutations.Here, we explored the advances made in SynCom research regarding plant health, focusing on bacteria, as they are the most dominant microbial form compared with other members of the microbiome and the most commonly found in SynCom studies.

Competition for iron is an important factor for microbial niche establishment in the rhizosphere. Pathogenic and beneficial symbiotic bacteria use various secretion systems to interact with their hosts and acquire limited resources from the environment. Bacillus spp. are important plant commensals that encode a type VII secretion system (T7SS). However, the function of this secretion system in rhizobacteria–plant interactions is unclear. Here we use the beneficial rhizobacterium Bacillus velezensis SQR9 to show that the T7SS and the major secreted protein YukE are critical for root colonization. In planta experiments and liposome-based experiments demonstrate that secreted YukE inserts into the plant plasma membrane and causes root iron leakage in the early stage of inoculation. The increased availability of iron promotes root colonization by SQR9. Overall, our work reveals a previously undescribed role of the T7SS in a beneficial rhizobacterium to promote colonization and thus plant–microbe interactions.

Iron (Fe) plays a central role in the vital processes of a plant. The Fe status of a plant influences growth and immunity, but it also dictates interactions of roots with soil microbiota through the production of Fe mobilizing, antimicrobial fluorescent phenolic compounds called coumarins. To adapt to low Fe availability in the soil, plants deploy an efficient Fe deficiency response. Interestingly, this Fe deficiency response is hijacked by root-colonizing microbes in the root microbiome to establish a mutually beneficial relationship. In this chapter, we describe how we cultivate plants and microbes to study the interaction between plants, beneficial rhizobacteria, and the plant’s Fe deficiency response. We describe (a) how we study activity and localization of these responses by assessing gene-specific promoter activities using GUS assays, (b) how we visualize root-secreted coumarins in response to Fe deficiency and colonization by beneficial rhizobacteria, and (c) how we prepare our samples for metabolite extraction and reverse-transcriptase quantitative PCR to analyze the expression of marker genes.

Hyaloperonospora arabidopsidis (Hpa) is an obligately biotrophic downy mildew that is routinely cultured on Arabidopsis thaliana hosts that harbour complex microbiomes. We hypothesized that the culturing procedure proliferates Hpa-associated microbiota (HAM) in addition to the pathogen and exploited this model system to investigate which microorganisms consistently associate with Hpa. Using amplicon sequencing, we found nine bacterial sequence variants that are shared between at least three out of four Hpa cultures in the Netherlands and Germany and comprise 34% of the phyllosphere community of the infected plants. Whole-genome sequencing showed that representative HAM bacterial isolates from these distinct Hpa cultures are isogenic and that an additional seven published Hpa metagenomes contain numerous sequences of the HAM. Although we showed that HAM benefit from Hpa infection, HAM negatively affect Hpa spore formation. Moreover, we show that pathogen-infected plants can selectively recruit HAM to both their roots and shoots and form a soil-borne infection-associated microbiome that helps resist the pathogen. Understanding the mechanisms by which infection-associated microbiomes are formed might enable breeding of crop varieties that select for protective microbiomes.

Insect herbivores are amongst the most destructive plant pests, damaging both naturally occurring and domesticated plants. As sessile organisms, plants make use of structural and chemical barriers to counteract herbivores. However, over 75% of herbivorous insect species are well adapted to their host’s defenses and these specialists are generally difficult to ward off. By actively antagonizing the number of insect eggs deposited on plants, future damage by the herbivore’s offspring can be limited. Therefore, it is important to understand which plant traits influence attractiveness for oviposition, especially for specialist insects that are well adapted to their host plants. In this study, we investigated the oviposition preference of Pieris butterflies (Lepidoptera: Pieridae) by offering them the choice between 350 different naturally occurring Arabidopsis accessions. Using a genome-wide association study of the oviposition data and subsequent fine mapping with full genome sequences of 164 accessions, we identified WRKY42 and AOC1 as candidate genes that are associated with the oviposition preference observed for Pieris butterflies. Host plant choice assays with Arabidopsis genotypes impaired in WRKY42 or AOC1 function confirmed a clear role for WRKY42 in oviposition preference of female Pieris butterflies, while for AOC1 the effect was mild. In contrast, WRKY42-impaired plants, which were preferred for oviposition by butterflies, negatively impacted offspring performance. These findings exemplify that plant genotype can have opposite effects on oviposition preference and caterpillar performance. This knowledge can be used for breeding trap crops or crops that are unattractive for oviposition by pest insects.