Imara Perera

The biology of plant-microbe interactions is an exciting area of research that suffers from an under-representation of scientists from a number of demographic groups. We believe that an approach that focuses on problems that today������������������s college students are passionate about will attract a greater diversity of students to the discipline. Incorporating research opportunities in plant-microbe interactions that address questions surrounding climate change, global food security, and sustainability will draw in students of varying interests and disciplines and will inspire them to pursue research not only for practical applications, but also to answer basic biological questions in plant and microbial biology. Integrative Microbial and Plant Systems will engage students in cutting-edge research using molecular biology and computational tools, encompassing basic and applied issues in plant and microbial sciences. It will encourage students to examine and understand plant-microbe community systems as a whole using ����������������OMICs��������������� approaches and will go beyond traditional biotechnology by challenging the students to identify key mechanisms underlying plant-microbe interactions and to use this understanding to improve plant growth and development, particularly in response to environmental stressors.

Plants are a vital part of human life support systems for long-duration space flight and habitation. However, the space environment is not optimal for plant growth. Plants grown in space are subject to many unfamiliar stresses (in addition to the lack of gravity) and recent transcriptional profiling studies indicate that there are global changes in gene expression between space and ground controls. Post transcriptional regulation of RNA is emerging as an important mechanism of modulating gene expression under different environmental conditions. To date however, there have been no studies to examine the role of small regulatory RNAs in plant responses to the space environment. We propose to examine the transcriptional and post transcriptional mechanisms that regulate early seedling development in space and microgravity. Our hypothesis is that plant adaptation and response to the space environment will involve novel regulatory small RNAs. Our previous flight experiment ����������������Plant Signaling��������������� has revealed novel regulatory mechanisms and provides the foundation for further investigation and the proposed research. The long term goals are to understand the molecular mechanisms by which plants sense and adapt to changes in their environment and to characterize the regulatory networks that mediate these responses. This knowledge will be valuable for designing plants which are better able to withstand space flight, microgravity, and adverse environmental conditions.

Several carbon capture mechanisms have emerged in plant systems that provide unique advantages to plants depending on their environment. For example, while most plants use a C3 photosynthesis mechanism, C4 and CAM carbon capture mechanisms can increase water use efficiency or temperature tolerance. These advantages have been well-characterized in the atmospheric CO2 levels on Earth, but in enclosed human habitats such as those needed for long-term space flight, CO2 levels far exceed that of Earth���s atmosphere. Altered CO2 levels affect nutritional content and water use efficiency, but this research has used CO2 levels below that on enclosed human habitats. This proposed work would examine how high CO2 levels affect the plant physiology and nutritional content of edible microgreens that use different photosynthetic mechanisms: C3, C4, and CAM. We will monitor physiological characteristics and the nutritional profile across different CO2 levels for these microgreen species with C3, C4, and CAM photosynthesis. The combined effects of altered CO2 levels and other spaceflight relevant stresses such as water availability will be examined to understand if these different photosynthetic mechanisms can provide advantages to enhance plant productivity in space environments. These results would provide important baseline information on plant nutrition and performance that is needed for planning long-term space missions and thus would address the following objectives of the solicitation and NASA program goals: Decadal Survey- Priority 3: A systematic suite of plant biology experiments to elucidate mechanisms by which plants respond and adapt to spaceflight, and to facilitate their eventual use in Bioregenerative Life Support Systems; PB-1 How does gravity affect plant growth, development & metabolism (e.g. photosynthesis, reproduction, lignin formation, plant defense mechanisms) and PB-3 How can horticultural approaches for sustained production of edible crops in space be both improved and implemented (especially as related to water and nutrient provision in the root zone)?

Plants will be a crucial component for astronaut health and well-being during any long-distance spaceflight or colonization mission: as a source of food, for replenishing water and purifying air as well as physiological and psychological comfort. The challenge is to understand how plants respond to the spaceflight environment to enable plants to thrive in potentially hostile environments. As technologies have advanced for global gene expression, transcriptome level research has become an integral part of experiments and provides knowledge of gene expression resulting from the conditions of spaceflight. Steady state transcript abundance quantified by RNASeq is frequently used as measure of gene expression with the implicit assumption that transcriptional changes upon a treatment (such as a stress) are indicative of the downstream response. However, changes in mRNA abundance do not necessarily lead to corresponding changes in protein, and transcript and protein abundance are not highly correlated. The data from spaceflight experiments BRIC20 (PI Wyatt) and Plant Signaling (PI Perera) suggest that post-transcriptional regulation plays an integral role in gene expression differences between spaceflight and ground controls. The differential expression, abundance and phosphorylation of translational machinery in spaceflight leads to the obvious questions: What genes are being post transcriptionally regulated and by what mechanism(s)? To answer these questions, PIs Wyatt and Perera plan to combine expertise and resources to generate compatible multi-omics datasets and provide a comprehensive picture of transcriptional and post transcriptional regulation. This integrated approach will help answer fundamental questions regarding plant adaptation to spaceflight and this proposal is aligned with sub-topic PL-A of Appendix B. The novel datasets and analyses will address questions outlined in Research Emphasis 2 of the Space Biology Science Plan 2016-2025, specifically ����������������(a) Answer basic questions about how plants respond to changes in gravity and other environmental factors associated with spaceflight. And (b) Build on past plant research to provide a better understanding of physiological responses of plants to spaceflight, providing new knowledge that can facilitate the development of a bioregenerative life support system���������������. Analyses will also addresses Research Emphasis 4: molecular and cellular biology, specifically ����������������(a) Studies designed to determine how spaceflight alters gene expression at the transcriptomic, metabolomics and proteomics levels in the different tissues or cell types within the same organism, and how these changes impact the organism������������������s overall health during space travel���������������.

The circadian clock, an internal timekeeping mechanism, enables organisms to temporally organize their molecular and biochemical activities so that they are optimally timed with environmental conditions. Many environmental responses are gated by the circadian clock. Responses to environmental stimuli vary depending on the time of day or season that it is perceived by the organism. We examined microarray and RNA-Seq data sets available in GeneLab and found that components of the circadian clock are often identified as differentially expressed in response to gravity in multiple studies in Arabidopsis. This finding led us to investigate the potential for gating of gravitropic responses such as root bending. We observed that the time of day the stimulus is provided affects the magnitude of the gravitropic response. Further, this response is altered in a circadian clock mutant. Based on these findings we hypothesize that, like other environmental stimuli, the response to gravity is gated by the circadian clock. We propose to investigate if there is an integrated relationship between the circadian clock and gravity. First, we propose to determine if the time of day and year can impact the observed effects of microgravity indicating that these factors should be considered in all microgravity research. Secondly we will examine if microgravity affects circadian-regulated activities and the timing of all aspects of physiology and development.