How protists contribute to plant growth and health: Exploring new interactions with the plant microbiome

The plant microbiome is a key determinant of plant fitness. Traditionally, research has focused on interactions involving a few microbial groups, such as bacteria and fungi, while other players, including protists, have been largely overlooked. Recently, protists have emerged as important regulators of plant microbiome diversity and functionality. Beyond providing direct ecological services, protists influence the structure of rhizosphere populations, promoting those with beneficial roles for plants. Emerging evidence further reveals that the regulatory effects of protists extend beyond the rhizosphere, shaping endophytic communities. As the importance of protists becomes increasingly evident, future crop production strategies must integrate their role as regulators of microbiome functionality and plant performance. • Protists play an important ecological role in diverse soil ecosystems. • Protists promote plant growth and health by modulating the soil microbiome. • New evidence suggests a more relevant role in shaping the plant endobiome.