Synthetic microbial community in pristine environment promotes the growth of the endangered plant Lilium tsingtauense.

BACKGROUND: Habitat fragmentation and degradation have led to the critical endangerment of numerous wild plant species. Although significant achievements in the conservation of endangered wild plants in various regions worldwide, the interaction mechanisms between these plants and their associated rhizosphere microorganisms have yet to be fully elucidated. RESULTS: Here, we present a communication model between the endangered wild plant Qingdao lily (Lilium tsingtauense) and its associated rhizosphere microorganisms. We isolated a rhizosphere fungus, Trichoderma longibrachiatum QDAU 0920, which effectively colonizes the roots of Qingdao lily and significantly promotes root growth. This growth enhancement is mediated by multiple plant hormones, with auxin playing a particularly prominent role. Further investigation revealed that a non-canonical AUX/IAA protein of the LtIAA16 may augment the transcriptional activation activity of LtARF22 by competitively interacting with LtIAA6, LtIAA17, and LtIAA11, thereby facilitating root growth in Qingdao lily. The growth-promoting effects of this interaction were subsequently validated in several other plant species, including tomato, pepper, corn, pumpkin, and cucumber. Notably, T. longibrachiatum QDAU 0920 forms synthetic microbial consortia (SynComs) in conjunction with other Trichoderma and Penicillium species. These SynComs consistently enhance the growth of Qingdao lily as well as other lily species such as L. lancifolium, Lilium 'Avalon Sunset', and Lilium 'Deliana'. CONCLUSION: Collectively, these findings underscore the considerable potential of native microorganisms in the development of plant growth-promoting agents and the conservation of endangered plant species. Video Abstract.