Mechanisms of nutrient sensing and homeostasis in plants

Plants require light, carbon dioxide, water, and mineral nutrients to grow. While sunlight and carbon dioxide are usually plentiful, water and mineral nutrients are often limiting factors for plant growth, making irrigation and fertilizers the two most costly inputs for crop production and sustainable agriculture. However, reliance on fertilizers is not a long-term solution because both production and application of fertilizers cause pollution and threaten the sustainability of our environment.

An alternative strategy is to breed crops with high nutrient use efficiency, but this requires understanding how plants acquire and utilize each nutrient, which is the subject of this research project. Discoveries from the project will be applied to crop improvement through ongoing collaborations with international and USDA labs associated with the PI’s laboratory.

The research will have an additional impact on undergraduate and graduate education through courses the PI teaches at UC Berkeley and through independent research programs in the PI’s laboratory. The project will also enhance the outreach efforts that focus on local high schools to encourage students of underrepresented groups to become interested in biology.

The project will support diversity and broaden participation of disadvantaged individuals, including support of one researcher with a disability.

Membrane transport is important for mineral nutrient homeostasis at the cell and whole plant level. To thrive, plants have evolved intricate mechanisms that maintain mineral homeostasis at the cellular and whole-plant level despite constantly changing nutrient status in soil. The PI’s lab discovered the calcium response modules (CBL-CIPK) that form a signaling network for nutrient sensing.

New results indicate that plants also utilize a conserved nutrient sensor, TARGET OF RAPAMYCIN (TOR), to integrate the high potassium (K) nutrient status to initiate “growth mode” and suppress the low-K response by degrading the CBL-CIPK modules. In a reciprocal manner, low-K-induced activation of CBL-CIPK network represses TOR activity and switch plants to “adaptation mode”, establishing a conceptual framework on how plants adapt to the changing nutrient status in the soil.

The same CBL-CIPK network activates sequestration of magnesium (Mg) into vacuole in response to high-Mg, providing a possible mechanism for integrating different nutrients cues. The recent discovery of Mg-transporters responsible for Mg-sequestration into (and remobilization out of) the vacuole set the stage for connecting the CBL-CIPK modules to the Mg-transporters, constructing a molecular relay from high Mg status in the serpentine soils (the signal), to the activation of CBL-CIPK modules (the signaling), and Mg sequestration into the vacuole (the response).

The specific objectives of this project are: 1. To identify the mechanisms by which the dual CBL-CIPK pathways are activated by low-K status; 2. To identify the events leading to K-induced activation of TOR and inactivation of CBL-CIPK network; and 3.

To dissect the CBL-CIPK pathway that governs Mg fluxes across the tonoplast. The research will benefit from the unique expertise of PI’s group in the model plant systems that are amenable to patch-clamp and cell biology analysis in combination with genetic and biochemical 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.