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The subcellular response during rhizobial infection in leguminous root hairs. (A) Fluorescence image of a 7-day-old nodule of Medicago with an IT in a curled root hair. Actin is pseudocolored in green, and rhizobia and ITs are magenta. Scale bars, 140 mm. (B) Curled root hair with an intact IT. Scale bar, 24 mm. (C) Rhizobia or purified Nod factors induce the expression of associated genes by directly binding Nod factors and Nod factor receptors, including nodulation pectate lyase (NPL), symbiosis-specific PME1 (SyPME1), SYMBIOTIC FORMIN 1 (SYFO1), membrane-associated flotillin 4 (FLOT4), and plantspecific remorin SYMREM1. Meanwhile, the microtubule and actin cytoskeleton in the tip of root hairs become transiently fragmented before recovering to guide IT initiation and elongation. The infectosome complex (VPY-LIN-EXO70H4-RPG) localizes to the IT tip and is required for maintaining IT polar growth by controlling secretion and vesicle trafficking. Cytoskeleton-associated proteins regulate the arrangement of the host cytoskeleton to guide the root-hair nucleus migration and IT elongation.
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The legume–rhizobium symbiosis represents the most important system for terrestrial biological nitrogen fixation on land. Efficient nitrogen fixation during this symbiosis depends on successful rhizobial infection and complete endosymbiosis, which are achieved by complex cellular events including cell-wall remodeling, cytoskeletal reorganizations,...
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Context 1
... leguminous plants, root hairs detect specific rhizobial signaling molecules known as Nod factors. The WMC continuum then responds transiently to the Nod factors, facilitating the subsequent intracellular invasion by rhizobia ( Figure 2). (C) Rhizobia or purified Nod factors induce the expression of associated genes by directly binding Nod factors and Nod factor receptors, including nodulation pectate lyase (NPL), symbiosis-specific PME1 (SyPME1), SYMBIOTIC FORMIN 1 (SYFO1), membrane-associated flotillin 4 (FLOT4), and plantspecific remorin SYMREM1. ...
Context 2
... genes Nap1 (Nckassociated protein 1) and Pir1 (121F-specific p53-inducible RNA), which encode proteins that are likely involved in the assembly of F-actin filaments, control the initiation and subsequent progression of ITs. Loss of function of Nap1 or Pir1 results in short root hairs characterized by transverse or web-like actin filaments, which lead to defects in IT-dependent root colonization (Yokota et al., 2009). ACTIN-RELATED PROTEIN COMPONENT 1 (ARPC1), which encodes a subunit of the major actin nucleator ARP2/3 complex, regulates rhizobial intracellular colonization in roots by altering actin arrangements in L. japonicus root hairs ( Hossain et al., 2012). ...
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