# Control of Macromolecular Traffic Through Plasmodesmata

> **NIH NIH R01** · STATE UNIVERSITY NEW YORK STONY BROOK · 2020 · $380,409

## Abstract

PROJECT SUMMARY
 Perhaps one of the most intriguing, yet least studied, aspects of macromolecular
transport is traffic through intercellular connections. These connections are termed tunneling
nanotubes (TNTs) in mammals and plasmodesmata (Pd) in plants. Whereas both mammalian
and plant viruses utilize cell-to-cell transport pathways, the first such capability was identified for
plant viruses, the transport of which via Pd represents a conceptual paradigm for intercellular
traffic of macromolecules. Tobacco mosaic virus (TMV), whose Pd transport is mediated by its
movement protein (MP), is used as tool to study the mechanisms of this transport.
 Pd transport comprises 3 sequential pathways (that remain obscure even 35 years after
identification of MP as the first Pd-moving protein): targeting to Pd, gating of Pd, and inactivation
of the Pd-gating factor to prevent further interference with intercellular communication. This
work focuses on these processes, using the following model: (1) In the cytoplasm, MP Pd
localization signal (PLS) interacts with SYTA, a synaptotagmin that mediates contacts between
the ER and plasma membrane (PM), and MP Pd-gating domain (PDG) interacts with ANK,
another plant factor required for viral movement. (2) SYTA directs MP to PM and (3) hands MP
to a Pd-associated protein PDLP4, resulting in Pd localization. (4) ANK (or ANK-MP complex)
activates Pd-associated ß-1,3 glucanase (PBG), which (5) relaxes the Pd callose sphincter and
elevates permeability. (6) MP then is destabilized by the ubiquitin/proteasome system.
 Aim 1. Mapping protein interactions in Pd targeting and gating. It is known that MP PLS
interacts with SYTA and PDLP4, and MP PGD interacts with ANK, which, in turn, interacts with
PBG. But it is not known whether these interactions occur in a single complex with all or some
of these proteins, or whether they are mutually exclusive. These interactions will be mapped in
vitro, in yeast, and in planta to define the functional pathway for MP targeting to Pd in
preparation for their gating. Aim 2. Pd gating mechanism. The hypothesis will be tested that MP
redirects ANK from the cytoplasm to Pd, where ANK (or ANK-MP complexes) activates PBG
and gates Pd. These experiments will define the functional pathway for MP gaiting of Pd. Aim 3.
UPS-mediated down-regulation of MP. Challenge with viruses or bacteria induces expression of
the plant defense-related F-box protein VBF. Among its pathogen-encoded substrates, VBF
recognizes MP. The hypothesis will be tested that VBF targets MP to proteasomal degradation
via the SCFVBF pathway. The expected outcomes of the proposed research will define basic
concepts and molecular pathways that underly intercellular transport of macromolecules.

## Key facts

- **NIH application ID:** 9995495
- **Project number:** 5R01GM050224-23
- **Recipient organization:** STATE UNIVERSITY NEW YORK STONY BROOK
- **Principal Investigator:** VITALY H CITOVSKY
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $380,409
- **Award type:** 5
- **Project period:** 1994-01-01 → 2022-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9995495

## Citation

> US National Institutes of Health, RePORTER application 9995495, Control of Macromolecular Traffic Through Plasmodesmata (5R01GM050224-23). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9995495. Licensed CC0.

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