Cold-tolerant bacteria from alpine Rosaceae plants modulate transcriptional responses of apple and strawberry plantlets to freezing stress.

Introduction: Freezing stress is a frequent challenge in agricultural systems and represents one of the major abiotic constraints on fruit production in Rosaceae crops. Plant-associated microorganisms can support plant survival under cold stress conditions, but little is known about the transcriptional responses stimulated by cold-adapted bacteria in host plants under freezing stress. This study aimed to investigate transcriptional responses activated in apple and strawberry plantlets to freezing stress following the inoculation with two cold-tolerant bacteria isolated from alpine Rosaceae plants. Methods: Plantlets were treated with sterile 10 mM MgSO Results: Cold-tolerant bacteria isolated from alpine Rosaceae plants decreased electrolyte leakage in apple and strawberry plantlets exposed to freezing stress. Moreover, freezing stress caused distinct transcriptional responses between mock- and bacterium-inoculated plants, as well as between the two crops. In mock-inoculated apple plantlets, freezing stress downregulated transcripts related to amino acid metabolism, lipid metabolism, and secondary metabolism. In contrast, Discussion: The inoculation with