PROJECT SUMMARY/ABSTRACT
Plasmodesmata (PD), plasma membrane-lined pores in the plant cell walls, allow trafficking of
small molecules, macromolecules, metabolites, signaling molecules and including hormones from
one plant cell to another. Several hormones have been found to traffic between cells via PD.
Interestingly, salicylic acid (SA), a plant defense hormone, does not traffic via PD but through the
apoplast. Nonetheless, SA is a critical hormonal signal that negatively regulates cell-to-cell
permeability in response to pathogen infection. Previous studies have shown SA to regulate PD
through regulated callose accumulation along the pores. A second effect of PD is to induce the
insertion of additional pores at existing PD leading to the formation of complex (branched) pores.
Because PD are very important for plant growth, development, and defense, we seek to
understand the molecular mechanisms involved in regulating PD function and formation. This
study will focus on investigating the cellular mechanisms of how SA regulates intercellular
trafficking by adjusting PD permeability. These studies will apply a combination of advanced
microscopic techniques and cell and molecular biology approaches to study how SA is connected
to PD transport in epidermal leaf tissues of Nicotiana benthamiana. The specific aims of the
research will determine the effects of SA alone or in combination with another defense hormone,
jasmonic acid, on PD structure and function. We will also investigate how the concentration of SA
and/or JA change PD permeability based on various times after exposure to the hormone (Aim
1); determine PD structure and the number of PD in SA-treated tissues relative to untreated
controls to examine hormone effects on PD formation (Aim 2); determine the effect of SA on
endocytosis and ER-PM contact sites as part of the process inserting new pores into existing cell
walls, (Aim 3). The results from this research will advance understanding of how hormones
influence intercellular trafficking and PD, and they will be of interest to basic plant scientists and
agricultural scientists.