Unravelling the Bacterial Community Composition of Valerianella locusta, A Cold-Tolerant Plant

Low temperatures greatly affect plant growth. In addition to the development of its own protection mechanisms, plants may rely on microorganisms to help them cope with cold. Because Valerianella locusta (lamb's lettuce) is a cold-adapted plant, it represents an interesting plant to understand how cold affects the root bacteriome. By means of amplicon sequencing of 16S ribosomal RNA genes, we identified the taxa forming the main cold root bacteriome of lamb's lettuce. The analysis of the root microbiome of a naturally growing V. locusta population and the study of the changes in the root microbiome of cultivated V. locusta grown under cold and ambient conditions allowed us to detect four cold-responsive families, of which Oxalobacteraceae presented the strongest shift under chilling temperatures. Moreover, the plant genotype had a small but significant effect on the response of the root bacteriome to cold. Finally, several bacterial candidates were discovered that may possibly alleviate the effect of low temperatures on plant fitness; namely, Massilia ASV2, Flavobacterium ASV5 and ASV11, or Acidovorax ASV20. However, currently, only 10 cold-enriched isolates could be obtained in cultivation, of which Flavobacterium R-83141; Polaromonas R-83176, R-83177, and R-83175; and Acidovorax R-83129 were able to increase either the root, shoot, or total fresh weight of a cold-sensitive ecotype of Arabidopsis thaliana (Cvi-0). Our results provide an overview of the taxa forming the root microbiome of this species and of the compositional shift that occurs under cold temperature treatment, demonstrating the impact of low temperatures on the composition of the root microbiome.Copyright (c) 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.