Non-nodulating plants are some of the most widely grown crops today. Exploiting their interactions with bacteria as plant growth promoters, could lead to more sustainable agriculture. Bacteria with genomic predisposition to nitrogen (N) fixation are of interest for reducing the environmental impact associated with N-fertilizers.Our work uses the cereal model Brachypodium dystachion and the bacteria Herbaspirillum seropedicae (Hs) 1 and Pseudomonas koreensis (Pk) 2. Brachypodium’s time-resolved physiological and molecular changes to the presence of a bacterium showed the plasticity of the plant system under bacterial modulation, at limiting N. The work was performed in easy to reproduce gnotobiotic systems, and integrated noninvasive plant phenotyping, elemental analysis, δ15N measurements, proteomics and lipidomics. In both cases we found recovery of N-deficiency symptoms about two weeks post-inoculation, with increased N content in inoculated plants. The association with Hs pointed to two modes of plant-microbe interaction (PMI) dependant on N availability, with indication of N-fixation at low N. Association with Pk resulted in decreased C in inoculated roots, indicating nutrient exchanges between Brachypodium and Pk. A trend toward decreased δ15N signatures did not fully confirm N-fixation by Pk, although Pk grew on N-free medium in vitro. Importantly, proteomic and lipidomic changes were detected in Brachypodium inoculated with Pk. Proteomic shifts were driven by both N availability and Pk, bringing central N metabolism proteins of low N inoculated plants to levels similar of high N plants. Lipidomic changes responded to N limitation alone.Thus, associative PMI offer multiple strategies to mitigate plant abiotic stress, and the potential molecular mechanisms will be discussed in this presentation.References 1. Kuang et al., (2022). Journal of Experimental Botany, vol 73, 5306–5321.2. Sanow et al., (2023). Molecular Plant-Microbe Interactions, vol 36, 536–548.
Borjana Arsova (Wed,) studied this question.