Plant Growth-Promoting Microorganisms (PGPMs) in Plant Tissue Culture: Roles in Regeneration, Metabolism, and Acclimatization

Abstract

Plant tissue culture offers a controlled platform for biodiversity conservation, clonal propagation, and the production of bioactive compounds; however, the exclusion of natural microbial partners limits morphogenesis, aerial and root system development, and acclimatization success. Biotization with Plant Growth-Promoting Microorganisms (PGPMs) has emerged as a strategy to re-establish functional plant-microbe interactions disrupted by axenization. This review compiles advances on PGPMs in plant tissue culture, emphasizing their roles in regeneration, secondary metabolism, and acclimatization, while identifying prospects for applied biotechnology. PGPMs influence phytohormone profiles, nutrient acquisition, and defense pathways, thereby improving rhizogenesis, shoot morphogenesis, and acclimatization performance. Molecular evidence indicates that PGPMs modulate hormonal signaling and nutrient assimilation pathways, providing a mechanistic basis for these beneficial effects. Studies demonstrate that endophytic bacteria, rhizobacteria, actinomycetes, and mycorrhizal fungi can enhance regeneration efficiency and promote stress tolerance in vitro. Despite these advances, the specificity of microbial strains, colonization dynamics, and long-term stability of plant-microbe associations remain poorly resolved. Standardized inoculation protocols combined with integrative multi-omics approaches will enable the rational design of host-specific microbial consortia and accelerate the translation of PGPM-based biotization into reproducible and scalable micropropagation systems.