Plant microbiota dysbiosis and the Anna Karenina Principle.

Microorganisms are associated with all plants, recently leading to the hologenome concept. We reviewed the assembly processes of plant microbiota and analyzed its structure during the emergence of dysbioses. In particular, we discussed the Anna Karenina Principle (AKP) based on Leo Tolstoy's assertion applied to plant microbiota: 'All healthy microbiota are alike; each disease-associated microbiota is sick in its own way.' We propose the AKP to explain how stochastic processes in plant microbiota assembly due to several external stressors could lead to plant diseases. Finally, we propose the AKP to conceptualize plant dysbioses as a transitory loss of host capacity to regulate its microbiota, implying a loss of function that leads to a reduction of the host's fitness.