Myosin-driven transport network in plants is functionally robust and distinctive

Abstract

Directional transport of intracellular cargoes by cytoskeleton-based motors is one of the signature features of eukaryotic cells. It was proposed that the last common ancestor of eukaryotes possessed several prototype motor proteins, including evolutionarily related kinesins and myosins (1, 2). Among these, there was an ancient myosin lineage that includes extant class V myosins conserved in animals, fungi, and Amoebozoa, and closely related class XI myosins conserved in green algae and plants (3, 4). Together with other recent studies, the paper by Kurth et al. in PNAS (5) uncovers a brand new mechanism underlying intracellular transport of myosin cargoes. Most importantly, the Kurth et al. paper shows that the green branch of the tree of life has evolved a very dense and largely unique endomembrane transport network empowered by myosins XI.It is well recognized that long-range cargo transport is actin-centric in fungal and plant cells but mostly relies on microtubule-based motors in vertebrates (6, 7). The transport systems based on myosins V and XI exhibit remarkable variability in their functions and molecular organization in fungi and plants, respectively. First of all, myosin XI motors have much higher velocities, often greater than one order-of-magnitude faster, than myosin V (8

Myosin XI-K is involved in root organogenesis, polar auxin transport, and cell division

“…All six individual MyoB compartments studied so far (MyoB1, MyoB2, MyoB7, MyoB12, MyoB13, and MyoB14) are associated with rapidly moving endomembrane vesicles that are involved in driving cytoplasmic streaming which, in turn, carries passively moving organelles and other vesicular compartments including secretory and endocytic vesicles ( Peremyslov et al , 2013 , 2015 ; Kurth et al , 2017 ). Thus, the myosin-MyoB compartments appear to be specialized in driving cytosol dynamics including endomembrane trafficking ( Citovsky and Liu, 2017 ).…”

Myosin VIII and XI isoforms interact withAgrobacteriumVirE2 protein and help direct transport from the plasma membrane to the perinuclear region during plant transformation

“…The movement of molecules, vesicles, and organelles along actin filaments relies on the highly conserved myosin motors (Avisar et al, 2008b; Madison and Nebenfuhr, 2013; Ueda et al, 2015; Citovsky and Liu, 2017). Myosins have actin-binding, ATPase, and cargo binding domains, and these activities contribute to a wide range of physiological processes, including root hair growth, organelle motility, tip growth of pollen tubes, and gamete nuclear migration (Prokhnevsky et al, 2008; Peremyslov et al, 2010; Kawashima and Tachikawa, 2014; Madison et al, 2015).…”

Creativity comes from interactions: modules of protein interactions in plants

“…Other PB1 domain proteins in Arabidopsis that have been characterized include the PHOX proteins, implicated in interactions with myosin and the separation of plastids [147,148], and a family of putative kinases including HCR1 involved in the response to hypoxia [149]. To the best of our knowledge, there are no examples of proteins that contain multiple PB1 domains.…”