N-dependent dynamics of root growth and nitrate and ammonium uptake are altered by the bacterium Herbaspirillum seropedicae in the cereal model Brachypodium distachyon

Abstract

N-fixation in cereals by root-associated bacteria is a promising solution to reducing chemical nitrogen fertilizer in agriculture. However, plant-bacterial responses are unpredictable across environments. We hypothesized that cereal responses to N-fixing bacteria are dynamic, depending on N supply and time. To quantify dynamics, the gnotobiotic, fabricated ecosystem (EcoFAB) was adapted to analyze N mass-balance, image shoot and root growth and measure gene expression of Brachypodium distachyon (Brachypodium) inoculated with N-fixing bacterium, Herbaspirillum seropedicae (Herbaspirillum). Phenotyping throughput of EcoFAB-N was 25-30 plants/h with open software and imaging systems. Herbaspirillum inoculation of Brachypodium shifted root and shoot growth, nitrate versus ammonium uptake, and gene expression with time; directions and magnitude depending on N availability. Primary roots were longer and root hairs shorter regardless of N, with stronger changes at low N. At higher N, Herbaspirillum provided 11% total plant N from sources other than seed or nutrient solution. The time-resolved phenotypic and molecular data, points to distinct modes of action: At 5 mM the benefit appears through N fixation; while at 0.5 mM the mechanism appears to be plant physiological, with Herbaspirillum promoting uptake of N from the root medium.Future work could fine-tune plant and root-associated microorganisms to growth and nutrient dynamics.

Reproducible growth ofBrachypodium distachyonin fabricated ecosystems (EcoFAB 2.0) reveals that nitrogen form and starvation modulate root exudation

“…The higher uptake of NH 4 relative to NO 3 for Brachypodium ( Fig. 2A ) was shown previously ( 38 ). The iN form drove bidirectional pH change in our spent medium ( Fig.…”

Multiomic Approaches Reveal Hormonal Modulation and Nitrogen Uptake and Assimilation in the Initial Growth of Maize Inoculated with Herbaspirillum seropedicae

“…The diazotrophic bacterium H. seropedicae, can affect the nitrogen metabolism of the plant host [ 25 , 26 , 48 , 49 , 50 ]. Using transcriptomic and proteomic approaches, this study allowed us to better understand how inoculation can modulate nitrogen acquisition and metabolism.…”

“…Five fresh roots of control and inoculated plants were scanned by a printer (Epson Expression 10000xL 1.8 v3. 49) to analyze the root system morphology to obtain images in the WinRhizo ® software (Regent Instruments Inc., Quebec, Canada). Analyzed parameters were: length, projected area, surface area, root volume, number of tips, and number of forks and crossings.…”

Rhizonet: Image Segmentation for Plant Root in Hydroponic Ecosystem

“…Biofuels represent renewable energy sources extracted from organic materials, such as plants or plant remnants, and can serve as an eco-friendly substitute for conventional fossil fuels 1 , 2 . Specifically, microbiomes play a pivotal role in nutrient cycling and the promotion of plant growth 3 , both of which are vital to the efficiency of bio-energy crop cultivation. Gaining insight into the plant roots can support research on the optimization of nutrient accessibility, improved nutrient absorption, and enhanced plant growth and biomass yield.…”