The transcriptional mechanism behind Mimosa pudica leaf folding in response to mechanical disturbance.

Abstract

Main conclusions: Repeated stress in Mimosa pudica reduces photosystem efficiency, alters gene expression, shifting from flavonoid biosynthesis to stress resistance pathways, offering insights for sustainable plant stress defense strategies. Mimosa pudica is a plant known for its ability to fold leaves in response to mechanical disturbances, which serves as a visible phenotypic stress marker. Leaf folding response occurs with a timing and an intensity that vary depending on the stimulus. This adaptive behavior may function as a defense mechanism, helping plant resist herbivores and environmental stressors. In this study, we investigated the gene regulatory networks underlying M. pudica leaf closure following single and multiple mechanical disturbances (whole pot drops). Chlorophyll fluorescence was measured as fast phenotypic indicator of transient or permanent photochemical damage, and transcriptional responses were measured to identify the key genes regulating phenotypic changes after single or multiple drops. A progressive reduction of the quantum yield of PSII revealed a lower electron transport rate in leaves subjected to one or more drops, which may indicate the onset of energy shortage, potentially caused by limited ATP availability that constrains both leaf movement and photosynthesis. The transcriptomic profiles revealed larger differences when plants were subjected to multiple drops than to a single drop, with respect to unstressed controls. Interestingly, following a single drop, the majority of up-regulated genes were associated with the flavonoid biosynthetic pathway. After multiple drops, however, genes associated with biotic and abiotic stress resistance pathways were predominantly up-regulated. These findings provide new insights into the gene regulatory networks driving stress-induced movements in M. pudica leaves and lay the groundwork for developing sustainable strategies for plant stress defense.