Terri Lomax

Human space exploration requires technologies that enable human survival in extremely hostile environments. Advanced life support systems that enable a sustainable human presence in space and habitation of planetary surfaces need to supply food, purify air, potable water, and protection from extreme temperatures, radiation, and other environmental conditions. NASA?s Strategic Plan therefore outlines: ?NASA also will develop and test technologies for power and autonomous systems that can enable more afford¬able and sustainable space exploration by reducing both consumables launched from Earth and the risks for mission operations. A key component of sustainable life support systems will be plants. Plants provide food, regenerate O2, and purify water. However, plants are adapted to the environments they encounter on Earth, including a constant gravitational force of 1-g. Very little is known about their ability to survive, develop, produce food and seeds in environments with low gravitational forces like space, or lunar and Martian surfaces. This proposal outlines work to identify potential targets and mechanisms which will lead to the development of plants with increased stress tolerance, improved root growth, and enhanced overall crop performance in low gravity environments. Research: Plant growth, development and responses to environmental stresses are integrated processes. Endogenous developmental programs are modified to survive and adapt to changes in the physical and chemical environment. Recently it was discovered that small RNAs (sRNA, 18-24 nucleotides long) which are heritable and systemic, are key elements in regulating gene expression in response to biotic and abiotic changes. Several different classes of sRNAs have been identified that are part of a non-cell autonomous and phloem-mobile network of regulators affecting transcript stability, translational kinetics, and DNA methylation patterns responsible for heritable transcriptional silencing (epigenetic). Nothing is known about the role of sRNAs in plants in response to gravity, mechanical or other abiotic stresses that will be encountered in Bioregenerative Life Support (BLS) Systems. To make these BLS systems sustainable, plant growth and performance over several generations in extreme environments must be guaranteed to ensure crew survival. Our hypothesis is that gravity-regulated sRNA metabolism is essential for plant growth, performance, and robustness to other abiotic stresses. The proposed research focuses on the identification of gravity-regulated sRNA targets and the functional characterization of gravity regulated sRNA networks in other abiotic stress responses relevant to sustainable plant growth in extreme environments, including extraterrestrial habitats. This research will identify new potential targets and mechanisms to develop plants with increased stress tolerance to improve root growth and overall crop performance in low gravity environments. Education and Public Outreach: We remain committed to a comprehensive approach to the enhancement of science education at all levels and the public appreciation of science. We intend to build on our established strengths in this area to actively promote the education and public outreach goals of NASA. Relevance to the NASA mission: Understanding the molecular basis of adaptation and integration of abiotic stress responses in plants will enable us to generate plants that will tolerate environmental conditions beyond their adaptive range on Earth for closed-loop bioregenerative life support systems.

Research: Plants are sessile and have to adjust their growth and development to the conditions they encounter. The roots of most land plants grow down into the soil where they anchor the plant and take up water and nutrients. Soils vary widely in they physical and chemical composition. The overall direction of root growth follows the vector of gravity (positive gravitropism). However, when physical restrictions (i.e. compacted soil, rock) prevent the root from growing downwards, their ability to sense and respond to mechanical impedance allows the root to change their direction of growth (thigmotropism) and/or overall development and morphology (thigmomorphogenesis). In addition roots sense and respond to their chemical environment (water, nutrients) and adjust their capability of nutrient uptake to the specific conditions (nitrate, ammonium, phosphate, pH, sugars, organic N, ions, heavy metals). To maximize nutrient uptake and anchoring, plants have to sense and respond to their environment, and integrate these responses for optimal root growth. In the absence of sufficient force of gravity (ì-gravity environment), it has been observed that roots avoid growing into a semi-solid nutrient medium. This aversion could be a thigmotropic response where the root grows away from mechanical impedance that it could easily penetrate in a 1xg environment. Several components of the sensing and signal transduction cascades in response to gravity and mechanical stimulation have been identified. We have shown that the integration of both responses is based on a set of common and stress-specific signal transduction pathways leading to common and specific changes in gene expression. Very little is known about the regulation of gene expression in response to gravity stimulation, and no components for the mechano-specific signal transduction pathways have been identified today. Our work focuses on the identification of sensing components in the signal transduction pathway of root responses to gravitational and mechanical stimulation and how these responses are prioritized and integrated to regulate gene expression and directing root growth and development. Education and Public Outreach: We remain committed to a comprehensive approach to the enhancement of science education at all levels and the public appreciation of science. We intend to build on our established strengths in this area to actively promote the education and public outreach goals of NASA. Additionally, we plan to conduct an Advanced Life Support Roadmap workshop which will bring together key stakeholders in plant biology, horticulture, microbiology, aerospace, energy, civil engineering, food science, modeling and other disciplines to develop a strategic advanced life support technology roadmap for the Global Exploration Strategy. In the workshop will engender collaborations among researchers in the U.S. and abroad. Relevance to the NASA mission: Understanding the molecular basis of adaptation and integration of abiotic stress responses in plants should allow us to generate crop plants that will be able to tolerate abiotic conditions beyond their adaptive range on earth.

Introduction NC State University, a Research I Land Grant institution, participated in Phase I of the Ph.D. Completion Project as a member of a consortium with two other southern, Land Grant universities ? The University of Georgia (UGA) and The University of Florida (UFL). The three universities examined PhD completion/attrition and time to degree based on a conceptual model that identifies four conditions for optimal doctoral completion:1) the right people apply for doctoral study. 2) The right applicants are admitted as doctoral students. 3) Students and faculty form productive working relationships. 4) Students experience social support from fellow students. Participating programs at NC State included twelve programs in the sciences, engineering and mathematics (STEM disciplines) as follows: Chemistry (CH), Computer Science (CSC), Economics (ECO), Mathematics (MA), Microbiology (MB), Civil, Construction and Environmental Engineering (CE), Physics (PY), Psychology (PSY), Sociology (SOC), Botany (BO), Genetics (GN) and Chemical Engineering (CHE).