Plant Actin Biology

Abstract

Actin is a major component of the plant cytoskeleton. Filamentous actin (F‐actin) contributes to the maintenance of the internal architecture of the cell, drives cytoplasmic streaming (the movement of components around the cytosol) and contributes to the process of cell division. The biochemistry of plant actin has many similarities to that of yeast and animals, but has developed its own strategies and molecular machinery to organize actin filaments. F‐actin provides tracks for myosin molecular motors to transport organelles at high velocities and actin is required for specific stages of vesicle trafficking that underpin cell growth and development. The means by which plant cells control the nucleation of new actin filaments from G‐actin have diverged considerably from yeast and metazoans. The unique aspects of the plant actin cytoskeleton are likely to have arisen from a combination of the environmental challenges to a sessile multicellular existence and a complex evolutionary history. Key concepts The basic principles of actin biochemistry applicable to animals, fungi and protists are conserved in plants but there are a number of specific modifications as plants do not possess the full complement of animal actin‐binding proteins. Actin filaments in plants have to fulfil unique functions. Actin focuses on the expansion of tip growing cells, maintains cytoarchitecture and responds to the environment (e.g. polarizing in response to pathogen stimulation). During cell division actin filaments participate in all major plant‐specific arrays. A stationary cell is NOT a physically inactive cell. Actin cables are exploited for organelle transport. Actin‐based transport tends to dominate over microtubule‐based movement. Plants utilize the fastest known type V myosin (known in plants as type XI) within the eukaryote kingdom. Polymerization dynamics are thought to add to trafficking capabilities as low levels of antiactin drugs disrupt vesicle delivery and fusion during cell growth yet preserve myosin‐mediated transport. New proteins and new domain combinations have become established in plants to regulate the actin cytoskeleton in accordance with the unusual demands placed on them. Importantly, these radical adaptations should not be considered purely in terms of a response to a sedentary way of life as the fungal kingdom has achieved such a conversion using arguably less radical cytoskeletal solutions. Consequently the impact of other unique facets of plant evolutionary history and niches must be considered.

CARK3-mediated ADF4 regulates hypocotyl elongation and soil drought stress in Arabidopsis

“…Loss of AUX1 (auxin transporter AUXIN RESISTANT 1) leads to failure of actin reorganization in response to IAA treatment ( Arieti and Staiger, 2020 ). ADF4 modulates auxin distribution and transport through regulating the dynamics of actin filaments, which is required for cell expansion ( Deeks and Hussey, 2009 ; Jiang et al., 2020 ). Additionally, ABA receptors PYL8 (RCAR3) and PYL9 (RCAR1) could interact with the transcription factor PIF3 to regulate hypocotyl elongation ( Qi et al., 2020 ).…”

Actin filaments altered distribution in wheat (Triticum aestivum) “Bending Root” to respond to enhanced Ultraviolet-B radiation

“…Actin filaments are a wide spread structure in cells. They contribute to the maintenance of internal architecture of the cell, drive cytoplasmic streaming (the movement of components through the cytosol), and contribute to the process of cell division (Deeks and Hussey, 2001). Actin filaments shift their patterns to respond to certain exogenous factors, including enhanced UV-B radiation (Chen and Han, 2016).…”