Interactions of meristem-associated endophytic bacteria

Abstract

Generally, all endophytes should be considered as a community that interacts with other symbiotic organisms, such as mycorrhiza. Even though an endophyte may colonize the plant systematically, communities colonizing the plant shoots normally differ to a degree from the root-associated endophytes. Meristem-associated shoot endophytic bacteria are often found as contaminants in plant tissue cultures started from shoot tips (buds) or embryos. Whereas root endophytic bacteria are reasonably well studied with respect to location and interactions with the host, not much is known about endophytes associated with shoot meristems. Endophytic bacteria have been localized in the meristematic tissues of buds and flowers by in situ hybridization and transmission electron microscopy. Meristem-associated endophytes may share some growth-promoting traits with the root endophytes, but likely additional mechanisms of actions exist. For example, such endophytes can produce adenine derivatives that induce growth of the host tissue. These endophytes may also affect the plant development by various ways. Some of them can co-synthesize secondary metabolites together with the plant host. Many more mechanisms remain to be determined by methods such as genomics and metabolomics, which are valuable tools for characterizing the interactions between the plant and endophytic bacteria.