Putting the squeeze on PDs – a role for RETICULONS in primary plasmodesmata formation
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Primary plasmodesmata (PD) arise at cytokinesis when the new cell plate forms. During this process, fine strands of endoplasmic reticulum (ER) are laid down between enlarging Golgi-derived vesicles to form nascent PD, each pore containing a desmotubule, a membranous rod derived from the cortical ER. Little is known about the forces that model the ER during cell-plate formation. Here we show that members of the reticulon (RTNLB) family of ER-tubulating proteins may play a role in formation of the desmotubule. RTNLB3 and RTNLB6, two RTNLBs present in the PD proteome, are recruited to the cell plate at late telophase, when primary PD are formed, and remain associated with primary PD in the mature cell wall. Both RTNLBs showed significant co-localisation at PD with the viral movement protein of tobacco mosaic virus, while super-resolution imaging (3D-SIM) of primary PD revealed the central desmotubule to be labelled by RTNLB6. FRAP studies showed that these RTNLBs are mobile at the edge of the developing cell plate, where new wall materials are being delivered, but significantly less mobile at its centre where PD are forming. A truncated RTNLB3, unable to constrict the ER, was not recruited to the cell plate at cytokinesis. We discuss the potential roles of RTNLBs in desmotubule formation.
Knox , K , Wang , P , Kriechbaumer , V , Tilsner , J , Frigerio , L , Sparkes , I , Hawes , C & Oparka , K 2015 , ' Putting the squeeze on PDs – a role for RETICULONS in primary plasmodesmata formation ' Plant Physiology , vol 168 , no. 4 , pp. 1563-1572 . DOI: 10.1104/pp.15.00668
Copyright © 2015 American Society of Plant Biologists. All rights reserved.
This work was supported by grant BB/J004987/1 from the British Biotechnology and Biological Sciences Research Council (BBSRC) to K.O and C.H and by The Leverhulme Trust (F/00 382/G) to C.H.