Living inside plants: bacterial endophytes

As current research activities have focused on symbiotic or parasitic plant–microbe interactions, other types of associations between plants and microorganisms are often overlooked. Endophytic bacteria colonize inner host tissues, sometimes in high numbers, without damaging the host or eliciting strong defense responses. Unlike endosymbionts they are not residing in living plant cells or surrounded by a membrane compartment. The molecular basis of endophytic interactions is still not well understood. Several traits involved in the establishment of endophytes have been elucidated. Culture-independent methods for community analysis and functional genomic as well as comparative genomic analyses will provide a better understanding of community dynamics, signaling, and functions in endophyte–plant associations.

► Value of culture-independent methods to study endophyte community dynamics and functions.
► Functional genomic analyses reveal features required for endophytic establishment.
► Endophytes elicit weak defense responses in compatible plant–endophyte combinations.
► Comparative genome analyses elucidate endophyte characteristics.