Cytoskeleton and Root Hair Growth

Root hairs are long tubular outgrowths of root epidermis cell that form to increase the root surface in order to assist in the uptake of water and nutrients from soil. Root hair development consists of two distinct processes: root hair initiation and tip growth. During both events, the dynamic organization of the cytoskeleton translates local signaling events into a focused growth response that is critical during root hair growth. Microtubules are primarily important for maintenance of the direction of tip growth. The actin cytoskeleton, on the other hand, is crucial for the selection of the root hair initiation site and maintenance of tip growth. The unique cytoskeletal organization found in growing root hairs controls the polar delivery of membranes to the apex in order to enlarge the cell unidirectionally. Signaling factors, such as calcium and reactive oxygen species, are instrumental in maintaining polarity of the cytoskeleton, vesicle trafficking, and ultimately root hair growth. Interestingly, these regulatory factors are interdependent upon each other, so that an elaborate set of feedback loops forms that results in a stable self-organized cell polarity.