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. THIS PROJECT IS IN ALIGNMENT WITH P2 ONE.OF THE HIGHEST PRIORITY RECOMMENDATIONS OF THE SPACE BIOLOGY RESEARCH FOCUS ON PLANT AND.MICROBIAL BIOLOGY AS OUTLINED IN THE DECADAL SURVEY REPORT "TO ANALYZE PLANT GROWTH AND.PHYSIOLOGICAL RESPONSES TO THE MULTIPLE STIMULI ENCOUNTERED IN SPACE FLIGHT ENVIRONMENTS".