Microtubule array formation during root hair infection thread initiation and elongation in the Mesorhizobium-Lotus symbiosis.
Nuclear migration during infection thread (IT) development in root hairs is essential for legume-Rhizobium symbiosis. However, little is known about the relationships between IT formation, nuclear migration, and microtubule dynamics. To this aim, we used transgenic Lotus japonicus expressing a fusion of the green fluorescent protein and tubulin-α6 from Arabidopsis thaliana to visualize in vivo dynamics of cortical microtubules (CMT) and endoplasmic microtubules (EMTs) in root hairs in the presence or absence of Mesorhizobium loti inoculation. We also examined the effect of microtubule-depolymerizing herbicide, cremart, on IT initiation and growth, since cremart is known to inhibit nuclear migration. In live imaging studies of M. loti-treated L. japonicus root hairs, EMTs were found in deformed, curled, and infected root hairs. The continuous reorganization of the EMT array linked to the nucleus appeared to be essential for the reorientation, curling, and IT initiation and the growth of zone II root hairs which are susceptible to rhizobial infection. During IT initiation, the EMTs appeared to be linked to the root hair surface surrounding the M. loti microcolonies. During IT growth, EMTs dissociated from the curled root hair tip, remained linked to the nucleus, and appeared to surround the IT tip. Lack or disorganized EMT arrays that were no longer linked to the nucleus were observed only in infection-aborted root hairs. Cremart affected IT formation and nodulation in a concentration-dependent manner, suggesting that the microtubule (MT) organization and successive nuclear migration are essential for successful nodulation in L. japonicus by M. loti.
Department of Life Science, International Christian University, 3-10-2 Osawa, Mitaka-shi, Tokyo, 181-8585, Japan, f.perrine-walker@latrobe.edu.au.
F M
FM
Perrine-Walker
M
M
Lartaud
H
H
Kouchi
R W
RW
Ridge
D021581:Active Transport, Cell Nucleus / Q000187:drug effects*; D017360:Arabidopsis / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins / Q000235:genetics; D006540:Herbicides / Q000494:pharmacology; D000070116:Lotus / Q000235:genetics / Q000382:microbiology*; D059128:Mesorhizobium / Q000254:growth & development*; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism*; D009946:Organothiophosphorus Compounds / Q000494:pharmacology; D055170:Plant Root Nodulation / Q000502:physiology; D018517:Plant Roots / Q000382:microbiology; D030821:Plants, Genetically Modified / Q000382:microbiology; D013559:Symbiosis; D014404:Tubulin / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D050257:Tubulin Modulators / Q000494:pharmacology
D006540:Herbicides; D009946:Organothiophosphorus Compounds; D014404:Tubulin; D050257:Tubulin Modulators; C549110:butamifos; D049452:Green Fluorescent Proteins