Microbiome and Exudates of the Root and Rhizosphere of Brachypodium distachyon, a Model for Wheat

Abstract

The rhizosphere microbiome is regulated by plant genotype, root exudates and environment. There is substantial interest in breeding and managing crops that host root microbial communities that increase productivity. The eudicot model species Arabidopsis has been used to investigate these processes, however a model for monocotyledons is also required. We characterized the rhizosphere microbiome and root exudates of Brachypodium distachyon, to develop it as a rhizosphere model for cereal species like wheat. The Brachypodium rhizosphere microbial community was dominated by Burkholderiales. However, these communities were also dependent on how tightly they were bound to roots, the root type they were associated with (nodal or seminal roots), and their location along the roots. Moreover, the functional gene categories detected in microorganisms isolated from around root tips differed from those isolated from bases of roots. The Brachypodium rhizosphere microbiota and root exudate profiles were similar to those reported for wheat rhizospheres, and different to Arabidopsis. The differences in root system development and cell wall chemistry between monocotyledons and eudicots may also influence the microorganism composition of these major plant types. Brachypodium is a promising model for investigating the microbiome of wheat.

Lost in diversity: the interactions between soil‐borne fungi, biodiversity and plant productivity

“…This finding suggests that niche differentiation over depth occurs among fungi (Jumpponen et al ., ; Unterseher et al ., ; Mujic et al ., ). Future work should reveal whether this depth differentiation is associated with decreased root biomass (Mueller et al ., ; Ravenek et al ., ), altered root exudation profiles (Kawasaki et al ., ) or differences in abiotic conditions (e.g. organic matter content; Cong et al ., ) across depths.…”

Feed Your Friends: Do Plant Exudates Shape the Root Microbiome?

“…Similarly, lateral roots are associated with distinct microbial communities, differing between tips and bases, as well as between different types of lateral root [14].…”

“…Sugars constitute a significant fraction of exudates, and are a main carbon source for microbes [ 6 3 7 _ T D $ D I F F ] [14,42]. Interestingly, many more sugar uptake than release systems have been described.…”

“…The success of microbial colonization of the rhizosphere depends on several aspects, such as chemotaxis, substrate specificity, competitiveness, and cooperativeness. [14,16,72,88], an environment distant from the more natural settings of plant microbiome studies. Furthermore, novel technologies enabling high-throughput screening of putative transporters against possible substrates are needed to reveal the impact of the respective substrates on the rhizobiome and, in turn, on plant health.…”

“…), compared with their respective wild relatives [5,[8][9][10][11]. Interestingly, not all plants have a rhizobiome distinct from bulk soil: some species, such as maize and lotus (Lotus japonicus) [12][13][14][15], have assembled a distinct rhizobiome, whereas other species, such as arabidopsis and rice, assembled a rhizobiome similar to bulk soil [3,5,7]. The former species display a strong, and the latter a weak rhizosphere effect ( Figure 1, Key Figure).…”