The KCH Kinesin Drives Nuclear Transport and Cytoskeletal Coalescence to Promote Tip Cell Growth in Physcomitrella patens

Long-distance transport along microtubules (MTs) is critical for intracellular organization. In animals, antagonistic motor proteins kinesin (plus end directed) and dynein (minus end directed) drive cargo transport. In land plants, however, the identity of motors responsible for transport is poorly...

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Bibliographic Details
Published in:The Plant cell 2018-07, Vol.30 (7), p.1496-1510
Main Authors: Yamada, Moé, Goshima, Gohta
Format: Article
Language:English
Subjects:
Actin
Calponin
Coalescence
Coalescing
Crosslinking
Cytoskeleton
Destabilization
Dynein
Filaments
Genes
Genomes
Growth rate
Homology
Kinesin
Microtubules
Molecular motors
Mosses
Nuclear transport
Nuclei (cytology)
Nuclei (nuclear physics)
Physcomitrella patens
Proteins
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Summary:Long-distance transport along microtubules (MTs) is critical for intracellular organization. In animals, antagonistic motor proteins kinesin (plus end directed) and dynein (minus end directed) drive cargo transport. In land plants, however, the identity of motors responsible for transport is poorly understood, as genes encoding cytoplasmic dynein are absent in plant genomes. How other functions of dynein are brought about in plants also remains unknown. Here, we show that a subclass of the kinesin-14 family, KCH (kinesin with calponin homology domain), which can also bind actin, drives MT minus enddirected nuclear transport in the moss Physcomitrella patens. When all four KCH genes were deleted, the nucleus was not maintained in the cell center but was translocated to the apical end of protonemal cells. In the knockout (KO) line, apical cell tip growth was also severely suppressed. KCH was localized to MTs, including at the MT focal point near the tip of protonemal cells, where MT plus ends coalesced with actin filaments. MT focus was not stably maintained in KCH KO lines, whereas actin destabilization also disrupted the MT focus in wild-type lines despite KCH remaining on unfocused MTs. KCH had distinct functions in nuclear transport and tip growth, as a truncated KCH construct restored nuclear transport activity, but not tip growth retardation of the KO line. Thus, our study identified KCH as a long-distance retrograde transporter as well as a MT cross-linker, reminiscent of the versatile animal dynein.
ISSN:1040-4651
1532-298X
DOI:10.1105/tpc.18.00038