RUI: The Translocation Mechanism of Nanomaterials in Plants

Nanomaterials, materials made up of structures ranging from 1-100 nanometers, are used worldwide in various sectors including medicine, agriculture, and industry. These materials are highly reactive in the environment and interact with elements available in soil and water, affecting their bioavailability for plants and microorganisms. The small size of metal-based nanomaterials results in a high rate of their uptake by living organisms including plants.

The impact of nanomaterials on living organisms and their toxicity level depends on various factors including their size, concentration, and type, as well as the exposed organism. Studies on the fate of nanomaterials in the environment have reported the potential of plants to accumulate nanomaterials. However, the exact mechanism of nanomaterials uptake and their fate in plants is not well understood.

Nanomaterials accumulated in plants can enter the human body through direct consumption of plants or through the food chain. Therefore, it is important to understand how they interact with plants to further protect public health and improve sustainable agricultural practices. This research project investigates the fate of the commonly used metal-based nanomaterial, silver nanoparticles, in plants and their interaction with essential plant nutrients such as potassium, magnesium, and zinc.

This will involve a series of molecular, physiological, and analytical studies to understand the form and the site of accumulation of silver nanoparticles in plants, in addition to their impact on membrane transporters. The PI will mentor undergraduate and master’s students during the study and provide educational and research opportunities for underrepresented minorities in STEM fields including women, first-generation college students, and people of color.

To improve public awareness about nanomaterials and their fate in plants, a three-dimensional model will be created based on the results of this study and will be displayed in a local science museum.

Nanomaterials are used worldwide in various sectors including medicine, agriculture, and industry. Silver nanoparticles are a common form of metal-based nanomaterials. These materials can be oxidized in the environment and be transformed into the ionic form, which is more interactive and toxic than the particulate form.

Silver nanoparticles, in either particulate or ionic form, impact plant physiology and metabolism at various levels including the membrane transporters and electrical potential, which subsequently affects plant water absorption and nutrient translocation. Silver nanoparticles are not needed for plant growth and there is not a membrane transporter specifically designated for silver nanoparticles to enter cells.

However, since plants can translocate and accumulate these nanoparticles in their tissues, there must be a transporter that allows these materials to pass across the membrane. Plasma membrane aquaporin and potassium channels are among the possible transporters for silver nanoparticles. Once these nanoparticles are taken up by plants, their presence in inter- and intra- cellular spaces changes the electrochemical potential of cells.

To provide equilibrium, the expression of several membrane transporters including proton ATPase, and cation and anion channels can be impacted. This in turn affects the movement of essential nutrients and water across the membrane, turgor pressure, and cytosolic and apoplastic pH level. These series of events can impact the structure of xylem cells and subsequently bioaccumulation and translocation of essential nutrients and water in plants.

Due to the role of aquaporins in the translocation of water, maintaining turgor pressure, and potentially transporting silver nanoparticles across the membrane, in this study tomato (Lycopersicon esculentum) and mutant for aquaporin PIP1 will be exposed to silver nanoparticles in order to determine the mechanism of translocation of these nanoparticles in plants and their interaction with plant essential nutrients. This project will include a series of analytical, molecular, and morphological analyses to achieve these aims, including the concentration, form, and site of silver nanoparticles accumulation in plants, the effects of their exposure on membrane transporters, and the impact of their exposure on vascular tissues.

Results will provide information in understanding the fate of nanomaterials in plants and to efficiently use plants for phytoremediation approaches.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.