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Marcela Pierce

Professor

Partners Building III 227

Bio

The vacuole is the major storage compartment in plant cells and has important implications for the nutritional value of agricultural crops. Our research is focused on identifying the molecular mechanisms that regulate the biogenesis of the vacuole and the delivery of tonoplast proteins to the vacuolar membrane. We use chemical and classical genetic approaches to characterize these mechanisms in the model plant Arabidopsis thaliana.

Plant vacuoles have additional functions in growth and development. Dynamics of vacuole fusion are also important for critical physiological functions such as the regulation of stomata closing during water deficit and gravitropism. Our lab is starting to elucidate molecular mechanisms of vacuole dynamics that may contribute to responses of plants to these environmental cues.

Courses Taught:

  • PB 780 Plant Molecular Biology (Fall)

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Education

Ph.D. Botany University of California 2003

B.S. Biology Universidad de los Andes, Colombia 1997

Area(s) of Expertise

Cell Biology, Vesicle Trafficking, Vacuole Biogenesis

Publications

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Grants

Date: 08/01/19 - 7/31/24
Amount: $1,005,876.00
Funding Agencies: National Science Foundation (NSF)

The plant vacuole is the most predominant organelle in plant cells, is essential, and can occupy up to 90% of the cell volume. Vacuole fusion is a dynamic process in cellular movements such as the opening of stomata. Stomata are pores on the leaf surface that regulate gas exchange and their movement can have large implications to carbon fixation, water loss and ultimately yield. Guard cell vacuoles are highly dynamic changing from a single large organelle in open stomata to a highly convoluted and sometimes fragmented vacuole in closed stomata. The proposed research will take advantage of available mutants with incomplete complements of SNARE and HOPS complexes to identify the rules that govern vacuole fusion control during stomata opening. An integrative systems biology approach combining genetics, biochemistry, quantitative microscopy and mathematical modeling will be used to develop a model of vacuole membrane dynamics during stomata movements.

Date: 02/17/20 - 6/30/24
Amount: $656,250.00
Funding Agencies: Game-Changing Research Incentive Program for Plant Sciences (GRIP4PSI)

Enabling the next generation of sustainable farms requires a paradigm shift in resource management of the two most critical agricultural inputs for food production: water and nitrogen (N) - based fertilizer. Inefficient management of these resources increases food production costs, decreases productivity, and impacts the environment. An integrated approach is needed to improve the sustainability and efficiency throughout the production chain. Emerging (bio)electrochemical (BEC) technologies offer alternatives to conventional, fossil-fuel intensive N fertilizer production. Recently our team has demonstrated two game-changing BEC technologies: 1) microbial conversion of nitrogen gas into ammonium, and 2) plasma generation of N species (e.g., nitrate, nitrite) and other reactive species in water for fertilization and anti-pathogen benefits. We will integrate these technologies to produce BEC, N-based fertilizer, and with advanced sensor and delivery systems, we will precisely supply fertilizers for sustainable precision agriculture. Our proposed approach focuses on the development of a novel “BEC fertigation on demand system” by using sensor-driven data and molecular analyses to investigate BEC fertigation impact on the plants’ growth, adaptation, and microbiome; its impact on food safety and quality, and its economic feasibility for on-farm deployment.

Date: 04/01/19 - 3/31/23
Amount: $299,922.00
Funding Agencies: National Science Foundation (NSF)

The aim of this exploratory EAGER is to generate the first plant-compatible inducible degron tool for inactivation of protein targets in plants. This system is urgently needed for analyses of cellular processes that are controlled by essential proteins, and to improve temporal resolution in protein knockdown experiments. Systems for the control of protein activity by protein degrons are revolutionizing animal and yeast cell biology, but they have so far been out of reach for plant biologists. The proposed system utilizes targeted ubiquitination and protein degradation via the proteasome and is inducible via a glucocorticoid receptor-Dexamethasome system. If successful, this system could be used to study the loss of any plant protein with high temporal resolution (e.g. within hours or minutes), which is not possible with any genetic tool available today. This system will also enable the characterization of essential proteins, for which the only genetic tool available today is induced RNA silencing. A fast, inducible system to control protein abundance in plants will be useful for plant biologists from any discipline to query the function of their favorite protein in real time.

Date: 10/29/18 - 10/28/22
Amount: $330,101.00
Funding Agencies: National Aeronautics & Space Administration (NASA)

This proposal will study the contribution f membrane contact sites to gravity sensing in Arabidopsis.

Date: 09/01/16 - 8/31/20
Amount: $539,132.00
Funding Agencies: National Science Foundation (NSF)

North Carolina State University faculty lack access to confocal microscopes that incorporate the latest technical advances for quantitative imaging, and this hampers their ability to provide valuable research training and education opportunities to undergraduate and graduate students and makes them less competitive in securing research funding. To train a well-prepared, knowledgeable workforce and to conduct world-class research, NCSU needs quantitative fluorescence microscopy applications such as 3-D Raster Image Correlation Spectroscopy and single molecule counting that cannot be accurately performed with existing equipment. In addition, NCSU has no super-resolution capability. The requested instrument will impact research and training programs across six NCSU colleges and numerous disciplines, including Cell and Molecular Biology, Biochemistry, Animal and Plant Developmental Biology, Plant Pathology, and Bio-Engineering, among others. The Zeiss LSM880 with Airyscan will enable NCSU faculty and students to 1) perform measurements with increased sensitivity and discrimination, 2) obtain fast temporal and spatial data, and 3) image live biological samples for longer times with reduced phototoxicity. The Zeiss LSM880 with Airyscan located within the Cellular and Molecular Imaging Facility (CMIF), a core research facility at NCSU, will provide training opportunities to students at all levels. In the past five years, 116 graduate students, 47 post docs, and 54 undergraduates as well as researchers from neighboring institutions (North Carolina Central University) and local industries have trained on the current confocal microscope, resulting in numerous publications and student poster presentations at international meetings and undergraduate research symposia. The new LSM880 with Airyscan will build on this success and expose students to state-of-the-art imaging applications. An innovative Light Microscopy Workshop will serve under-represented students from local Historically Black Colleges and Universities and a local women’s college.

Date: 07/02/13 - 7/01/18
Amount: $565,942.00
Funding Agencies: National Aeronautics & Space Administration (NASA)

A challenge to cultivation of plants in space is the effect of an altered magnitude of the force of gravity on plant growth and reproduction. If humans are to grow plants successfully in space, it is critical to understand how plants respond to changes in gravity, including the molecular mechanisms for perception and response. Plants respond to changes in gravity vector by alterations of plant growth and development, and this response is in part mediated by the endomembrane system. A critical role of the endomembrane system in the gravitropic response is well established as several protein trafficking mutants are agravitropic, however, the mechanisms by which endomembranes contribute to the perception and response to gravity stimulation are still unknown. Proper vacuole biogenesis seems to be a requirement for gravitropism, as the sedimentation of amyloplasts in shoot endodermal cells is impaired in mutants with defective vacuoles. However, the molecular mechanism for vacuolar control of amyloplast sedimentation has not been identified. This project seeks to identify mechanisms of vacuolar membrane fusion that are necessary for gravitropic perception.

Date: 02/01/13 - 1/31/17
Amount: $488,802.00
Funding Agencies: National Science Foundation (NSF)

The plant vacuolar membrane or tonoplast is essential for the storage of metabolites and hormones, the sequestration of ions and the maintenance of cellular turgor. All of these tonoplast functions are regulated by integral membrane proteins, and yet virtually nothing is known about the mechanisms for regulating the trafficking of membrane proteins to the tonoplast. To improve plant stress tolerance and ultimately increase the nutritional value of plants for human consumption, it is essential that we understand how to regulate vacuolar membrane biogenesis. Our hypothesis is that a Golgi-independent pathway for tonoplast protein trafficking is required for specific developmental processes such as vacuole maturation, and alterations in this pathway have profound effects on plant viability. In addition, we propose that phosphoinositides have a key role in homotypic fusion of tonoplast membranes and ultimately regulate the accumulation of tonoplast proteins in a large central vacuole. To test these hypotheses, we identified several impaired tonoplast trafficking (itt) mutants and small molecules that cause with defects in trafficking of a tonoplast protein. The specific aims of this project are: 1) To genetically dissect the Golgi-independent pathway for tonoplast-protein targeting. 2) To determine the role of phosphoinositides and VTI11 in tonoplast membrane fusion. 3) To identify the mechanism(s) for C834 inhibition of tonoplast-protein targeting.

Date: 07/01/10 - 6/30/13
Amount: $20,000.00
Funding Agencies: NCSU NC Space Grant Consortium

The plant response to gravitropic stimuli is in part mediated by the endomembrane system, as several protein trafficking mutants display an abnormal gravitropic response. Proper biogenesis of the plant vacuole seems to be a requirement for gravitropism, but the molecular mechanism for this interaction has not fully been identified. This project seeks to characterize the cross-talk between the gravitropic signaling and protein trafficking pathways by a chemical genetic approach. Several chemical inhibitors of gravitropism and/or protein trafficking to the vacuole have been identified previously. Our goal is to characterize the effects of a few these inhibitors at the cellular and physiological levels in order to gain insight into molecular mechanisms that are common to these two pathways.

Date: 02/15/10 - 1/31/12
Amount: $99,971.00
Funding Agencies: National Science Foundation (NSF)

The plant tonoplast is essential for the storage of metabolites and hormones, the sequestration of ions and the maintenance of cellular turgor. While these tonoplast functions are regulated by integral membrane proteins, virtually nothing is known about the mechanisms for regulating the trafficking of these proteins to the tonoplast. To improve plant stress tolerance and ultimately increase the nutritional value of plants for human and animal consumption, it is essential that we understand how to regulate vacuolar membrane biogenesis. We will use classical and chemical genetic approaches to characterize mechanism of trafficking of membrane proteins. Our specific aims are to: 1) Reveal critical proteins in the pathway by characterizing three mutants that are hypersensitive to Gravacin, a small chemical inhibitor of membrane biogenesis identified in a previous screen. 2) Identify mutants impaired in the targeting of tonoplast proteins. 3) Identify small inhibitors that induce mis-localization of the tonoplast marker. Both mutants and inhibitors will define the distinct pathways of membrane proteins to the vacuole. This research will have a major impact in our understanding of vacuole biogenesis and our ability to improve plants with enhanced vacuolar content.


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