AS KEY COMPONENTS OF BIOREGENERATIVE LIFE-SUPPORT SYSTEMS PLANTS WILL BE EXPOSED TO MULTIPLE STRESSES ASSOCIATED WITH SPACEFLIGHT. EXPERIMENTS CARRIED OUT IN SPACE HAVE DRAMATICALLY IMPROVED OUR UNDERSTANDING OF PLANT RESPONSES TO MICROGRAVITY. IN TURN THIS NOVEL KNOWLEDGE HAS ALLOWED THE DESIGN OF BETTER CULTURING METHODS THAT ENABLE PLANT DEVELOPMENT AND REPRODUCTION IN SPACE. YET TO DESIGN EVEN BETTER GROWTH STRATEGIES AND DEVELOP OPTIMIZED GENOTYPES FAVORABLE TO PLANT GROWTH AND PRODUCTIVITY DURING SPACEFLIGHT WE NEED TO BETTER UNDERSTAND THE MOLECULAR MACHINERY THAT CONTRIBUTE TO THE PERCEPTION OF AND RESPONSE TO GRAVITY AND/ OR MICROGRAVITY. UNFORTUNATELY THE LARGE COST ASSOCIATED WITH SPACE EXPERIMENTATION AND LIMITED ACCESSIBILITY TO THE RESOURCES NEEDED FOR SUCH EXPERIMENTATION LIMIT OUR ABILITY TO ACQUIRE THIS NEW KNOWLEDGE. CONSEQUENTLY UTILIZATION OF DEVICES THAT MIMIC MICROGRAVITY IS VIEWED AS A VIABLE ALTERNATIVE. THE 2D-CLINOSTAT HAS OFTEN BEEN UTILIZED FOR THIS PURPOSE. BY CONSTANTLY CHANGING THE ORIENTATION OF BIOLOGICAL SPECIMENS RELATIVE TO GRAVITY THESE DEVICES PREVENT GRAVITY-VECTOR DETECTION THEREBY TRIGGERING BEHAVIORAL RESPONSES THAT ARE SIMILAR TO THOSE EXPRESSED UNDER TRUE MICROGRAVITY. THE 2D-CLINOSTAT HAS OFTEN BEEN USED TO ESTIMATE THE SENSITIVITY OF PLANT ORGANS TO DIFFERENT DOSES OF GRAVI-STIMULATION. IN THIS CASE LOW DOSES OF GRAVI-STIMULATION ARE PROVIDED AT THE BEGINNING OF THE EXPERIMENT. STIMULATED SEEDLINGS ARE SUBSEQUENTLY CLINOROTATED FOR 4-5 HOURS ALLOWING FOR A CURVATURE TO DEVELOP IN RESPONSE TO THE INITIAL STIMULUS. YET THE DATA DERIVED FROM THESE ANALYSES ARE LIKELY TO BE SIGNIFICANT ONLY IF THE CLINOROTATION DOES NOT INTRODUCE ARTIFACTS OF ITS OWN. IN EXPERIMENTS INVOLVING ARABIDOPSIS THALIANA SEEDLINGS WE PREVIOUSLY OBSERVED A STRONG CLINOSTAT EFFECT ON ROOT SKEWING ON HARD AGAR SURFACES. FOLLOW-UP EXPERIMENTS INVOLVING BRACHYPODIUM DISTACHYON CONFIRMED A CLEAR IMPACT OF LOW-SPEED CLINOROTATION ON DIRECTIONAL ROOT-TIP BENDING. THESE EXPERIMENTS ALSO SUGGESTED AN IMPORTANT ROLE FOR THE FIRST CYCLE OF CLINOROTATION IN SETTING UP A SPECIFIC DIRECTION OF GRAVISTIMULATION AS LONG AS IT IS PROVIDED FOR A SUFFICIENTLY LONG TIME PERIOD. THE GENERAL OBJECTIVE OF THIS RESEARCH PROJECT WILL BE TO INVESTIGATE THE EFFECT OF LOW SPEED CLINOROTATION ON BRACHYPODIUM ROOT GROWTH. SPECIFIC OBJECTIVES INCLUDE: AIM 1: DEVELOP HIGH THROUGHPUT TIME-LAPSE IMAGING TO DESCRIBE THE DEVELOPMENT OF B. DISTACHYON ROOT CURVATURE RESPONSES TO CLINOROTATION AT HIGH SPATIO-TEMPORAL RESOLUTION; AIM 2: USE TRANSGENIC B. DISTACHYON SEEDLINGS THAT EXPRESS AUXIN-LEVEL AUXIN-FUNCTION AND AUXIN-EFFLUX CARRIER REPORTERS TO INVESTIGATE THE EFFECT OF CLINOROTATION ON AUXIN DISTRIBUTION AND SIGNALING ALONG THE ROOT TIP AND ON THE DISTRIBUTION OF AUXIN TRANSPORTERS BETWEEN FLANKS OF CLINOROTATED ROOT TIPS; AIM3: USE A COMBINATION OF GENOME WIDE ASSOCIATION STUDY (GWAS) AND RNA SEQ STRATEGIES TO IDENTIFY CANDIDATE GENES THAT MAY CONTRIBUTE TO ROOT-TIP RESPONSE TO CLINOROTATION AND USE REVERSE GENETICS TO INVESTIGATE THE ROLE(S) OF SUCH CANDIDATES AND OF GRAVITROPISM-RELATED GENES IN THE PROCESS. OVERALL THIS PROJECT WILL IMPROVE OUR UNDERSTANDING OF HOW LOW-SPEED CLINOROTATION AFFECTS ROOT GROWTH BEHAVIOR. WHILE OUR OBSERVATIONS SUGGEST A NEED FOR GREATER CAUTION IN USING A LOW-SPEED 2D CLINOSTAT AS A MICROGRAVITY-MIMIC SYSTEM THEY ALSO SUGGEST A NOVEL METHOD TO INVESTIGATE THE MOLECULAR MECHANISMS THAT CONTRIBUTE TO GRAVITY SENSING IN PLANTS ONE OF THE MAIN OBJECTIVES OF THE SPACE BIOLOGY PROGRAM. THIS PROJECT WILL INTRODUCE UNDERGRADUATE STUDENTS TO THE IDIOSYNCRASIES OF SCIENTIFIC RESEARCH IN SPACE BIOLOGY WHILE ALSO PUTTING A STRONG EMPHASIS ON UNDERGRADUATE AND K-12 EDUCATION AND PUBLIC OUTREACH.