plants Article Leaf Plasmodesmata Respond Differently to TMV, ToBRFV and TYLCV Infection Yaarit Kutsher, Dalia Evenor, Eduard Belausov, Moshe Lapidot and Moshe Reuveni *   Citation: Kutsher, Y.; Evenor, D.; Belausov, E.; Lapidot, M.; Reuveni, M. Leaf Plasmodesmata Respond Differently to TMV,ToBRFV and TYLCV Infection. Plants 2021, 10, 1442. https://doi.org/10.3390/ plants10071442 Academic Editor: Juan Antonio García Alvarez Received: 9 June 2021 Accepted: 12 July 2021 Published: 14 July 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Plant Science Institute, ARO, Volcani Center, 68 Hamakabim Rd, P.O. Box 15159, Rishon LeZion 7528809, Israel; yaarit@volcani.agri.gov.il (Y.K.); vhevenor@volcani.agri.gov.il (D.E.); eddy@volcani.agri.gov.il (E.B.); lapidotm@agri.gov.il (M.L.) * Correspondence: vhmoshe@agri.gov.il Abstract: Macromolecule and cytosolic signal distribution throughout the plant employs a unique cellular and intracellular mechanism called plasmodesmata (PD). Plant viruses spread throughout plants via PD using their movement proteins (MPs). Viral MPs induce changes in plasmodesmata’s structure and alter their ability to move macromolecule and cytosolic signals. The developmental distribution of a family member of proteins termed plasmodesmata located proteins number 5 (PDLP5) conjugated to GFP (PDLP5-GFP) is described here. The GFP enables the visual localization of PDLP5 in the cell via confocal microscopy. We observed that PDLP5-GFP protein is present in seed protein bodies and immediately after seed imbibition in the plasma membrane. The effect of three different plant viruses, the tobacco mosaic virus (TMV), tomato brown rugose fruit virus (ToBRFV, tobamoviruses), and tomato yellow leaf curl virus (TYLCV, begomoviruses), on PDLP5- GFP accumulation at the plasmodesmata was tested. In tobacco leaf, TMV and ToBRFV increased PDLP5-GFP amount at the plasmodesmata of cell types compared to control. However, there was no statistically significant difference in tomato leaf. On the other hand, TYLCV decreased PDLP5-GFP quantity in plasmodesmata in all tomato leaf cells compared to control, without any significant effect on plasmodesmata in tobacco leaf cells. Keywords: plant viruses; plasmodesmata; TYLCV; TMV; ToBRFV; tobacco mosaic virus; tomato yellow leaf curl virus; tomato brown rugose fruit virus 1. Introduction The dispersal of macromolecule and cytosolic signals throughout the plant depends on utilizing a unique intracellular apparatus called plasmodesmata (PD). A single plasmod- esma is a membrane-coated channel that traverses the cell walls, enabling the transport of molecules and communication between plant cells. The plasmodesmata’s outer membrane is part of the cell’s plasma membrane (PM), and the inner section is part of the endoplasmic reticulum (ER) network. Neighboring plant cells are therefore forming an intracellular domain that connects them directly. Although cell walls are permeable to small soluble proteins and other molecules, plasmodesmata allow direct, regulated, symplastic commu- nication between the cells [1]. Plasmodesmata are tubular, with a central membranous component, the desmotubule, a continuation of the ER lumen, with protein bridges to the plasma membrane that link the PD’s external borders. Macromolecules move between cells through the plasmodesmata within the desmotubule or in the gaps between the plasma membrane and the ER membrane in the plasmodesmata and can be mimicked artificially by selectively forming membrane pores [2]. Plant viruses spread cell-to-cell throughout the plant via PD [3]. Viruses encode movement proteins (MPs) to facilitate their flux through the plasmodesmata channel [4,5]. Tobamoviruses like tobacco mosaic virus (TMV) and tomato brown rugose fruit virus (ToBRFV) have a MP that in the case of TMV was shown to affect plasmodesmata [4,5] While in begomoviruses like tomato yellow leaf curl virus (TYLCV), which is used in this study, Plants 2021, 10, 1442. https://doi.org/10.3390/plants10071442 https://www.mdpi.com/journal/plants