Thigmomorphogenesis (from Ancient Greek θιγγάνω (thingánō) to touch, μορφή (morphê) shape, and γένεσις (génesis) creation) the phenomenon by which plants alter their growth and development in response to mechanical stimuli, exemplifies their remarkable adaptability to fluctuating environmental conditions.
From subtle forces such as wind or rain to deliberate touch, these stimuli trigger a cascade of cellular and molecular responses, shaping plant architecture to optimize survival and ecological fitness.
[2] At its core, thigmomorphogenesis involves the perception of mechanical forces by cellular mechanosensors, their transduction into biochemical signals, and subsequent changes in gene expression and hormone activity.
[3] This response integrates diverse molecular players, including mechanosensitive ion channels, receptor-like kinases, cytoskeletal elements, phytohormones, and transcription factors, which collectively drive both immediate and long-term morphological adaptations.
[4][5] The cytoskeleton, composed of microtubules and actin filaments, plays a vital role in plant mechanotransduction by linking mechanical stimuli to intracellular signaling cascades.
Disruption of microtubules using drugs like colchicine completely inhibits tendril coiling in Pisum sativum, demonstrating their essential role in responding to mechanical cues.
[6] The microtubule network interacts dynamically with the plasma membrane, influencing the activation of mechanosensitive ion channels (MSCs) and other proteins involved in signal transduction.
[3][6] While actin filaments are less directly involved in sensing mechanical stimuli, they are crucial for maintaining cellular integrity and facilitating localized growth responses.
[4] Together, the microtubule and actin networks provide a robust structural framework for the mechanotransduction machinery, ensuring efficient integration of external mechanical forces into the plant's developmental and physiological processes.
[1] Receptor-like kinases (RLKs), such as FERONIA (FER) and THESEUS1 (THE1), are critical components of the plant mechanosensory system, bridging extracellular mechanical stimuli with intracellular signaling.
[5] THE1, another RLK, specifically contributes to cell wall integrity signaling during mechanical stress by detecting cellulose biosynthesis defects and coordinating compensatory responses.
[7] These transmembrane proteins convert physical forces into ionic fluxes, most commonly involving calcium ions (Ca²⁺), which act as a universal second messenger in signal transduction pathways.
By gating Ca²⁺ influx, these channels facilitate downstream processes such as cytoskeletal rearrangements and hormone signaling that enable root growth under challenging conditions.
In species like Phaseolus vulgaris and Arabidopsis thaliana, mechanical stimulation induces enzymes involved in lignin biosynthesis, leading to thicker and more rigid stems.
By integrating mechanical signals with growth and defense pathways, plants achieve an optimal balance between structural reinforcement, stress tolerance, and resource allocation.