The plant immune system in heterogeneous environments.

The plant immune system inhibits pathogen growth and contributes to shaping a healthy microbial community in the plant body. Plants must appropriately respond to both microbial signals and abiotic factors that are diverse in time and space, and thus, proper integration of these inputs at local and systemic levels is of crucial importance for optimal plant responses and fitness in nature. Here, we review our current knowledge of three properties of the plant immune system, resilience, tunability, and balance, which enable plants to deal with complex cocktails of environmental factors. We also discuss future challenges on the path towards a comprehensive understanding of the interactions between plant immunity and pathogenic, non-pathogenic, and beneficial microbes.