A Seedling Growth Inhibition Assay to Measure Phytocytokine Activity

The study of immunomodulatory peptides, both of exogenous and endogenous origin, attracted increasing attention over the last years. Numerous methods are widely used to study the sensitivity of plants to peptide elicitation, ranging from measuring early to late induced responses. Seedling growth inhibition is a prominent and easy-to-measure output induced by prolonged peptide treatment. Here, we describe a robust Arabidopsis thaliana seedling growth inhibition experiment that can be used to measure the direct growth-inhibitory effect of peptides, exemplified by RAPID ALKALINIZATION FACTOR 23 (RALF23) treatment. We also show how the assay can be used to assess the modulatory effect of peptide co-treatment on microbe-associated molecular pattern (MAMP)-triggered seedling growth inhibition, exemplified by GOLVEN 2 (GLV2)`s effect on flagellin (flg22)-induced seedling growth inhibition.