Fig. 3: Genetic approaches to broaden the host range of
beneficial microbes. Microbe-derived effector proteins can be
engineered to block host defenses and initiate symbiosis (A). Genetic
engineering approach to recreate nodule organogenesis in non-legume
plants. The Myc-receptor, which recognizes AMF-produced Myc-factors, has
been engineered to perceive Nod factors by replacing the outer domain of
the receptor. This induces the formation of nodule-like structures by
activating a common symbiotic signaling pathway (CSSP) (B). Another
approach is to facilitate the association between nitrogen-fixing
microbes and cereals including rhizopine synthesis in plants such as
wheat and rice. Rhizopine is sensed by nitrogen-fixing bacteria via
biosensor plasmids that encode rhizopine-binding proteins and
rhizopine-dependent transcription factors (TF). These proteins drive the
downstream expression of genes encoding proteins required for nitrogen
fixation (C). Finally, the recruitment of root-associated microbiota is
dependent on host genetics. Genome wide association study mapping will
identify novel host genetic loci that control microbial selection to
facilitate breeding efforts to improve crop resilience (D).