HARNESSING RHIZOBIAL REGULATION MECHANISMS DURING LEGUME SYMBIOSIS TO IMPROVE SYNCOM PERFORMANCE IN SUSTAINABLE AGRICULTURE

Abstract

Global food security is threatened by the effects of climate change on agriculture, a key driver of economy and prosperity. The use of curated synthetic microbial communities (SynComs) in sustainable agriculture as a way to improve plant resilience in the face of external stressors is a promising solution to this problem. However, due to our limited understanding of long-term microbe-plant interactions, implementing SynComs in agricultural field settings is challenging. In this sense, the research we propose aims to bridge the knowledge gap of gene regulation mechanisms in bacteria under symbiotic relations with the soybean legume. Here, we focus our attention on a microbe with previously established nitrogen fixation enhancement potential in SynComs: the Bradyrhizobium elkanii (B. elkanii) rhizobium. Building on the findings of recent research, we utilise a strain-specific transcriptomics pipeline to isolate B. elkanii transcripts from the soybean root microbiome. This way, we will establish a set of transcription factors (TFs) showing exclusive gene upregulation in functional nitrogen-fixing plant nodules. These results will be integrated in vivo, assessing the regulators’ functional roles by phenotyping corresponding CRISPR-dCas9 knockdown mutants for nitrogen fixation and growth promotion in soybean plants. At last, we set out to explore the regulators’ mechanistic functionalities by identifying gene sequences and residues linked to evolutionary selective pressure. A rational mutagenesis strategy will then be employed to engineer the TFs for improved DNA binding affinity and stability, paving the way for a more resilient impact of microbes within SynComs. If successful, the research showcased in this proposal could represent a stepping stone towards more efficient SynCom consortia, ultimately ensuring sustainable agricultural practices and future-proof food security.