THIS PROPOSAL SEEKS TO UNDERSTAND THE INTERACTION OF THE ACTIN CYTOSKELETON GRAVITY AND ROOT GROWTH..SPECIFIC GOALS TO BE ACCOMPLISHED IN THE REMAINING FUNDING PERIOD ARE: (1) CHARACTERIZE AUTONOMIC.STRAIGHTENING IN MAIZE ROOTS IN RESPONSE TO BRASSINOLIDE- AND LATRUNCULIN B-INDUCED ACTIN.DISRUPTION. THIS WILL BE ACCOMPLISHED BY ANALYSIS OF ROOT GROWTH ON THE CLINOSTAT AND RANDOM.POSITIONING MACHINE AND THE MONITORING OF ACTIN DISTRIBUTION USING IMMUNOCYTOCHEMISTRY AND.PATTERNS OF GENE EXPRESSION USING QPCR. (2) EVALUATE ROOT GROWTH OF SELECTED ARABIDOPSIS ACTIN.SINGLE AND DOUBLE MUTANTS AND OF PEROXIDASE MUTANTS ON MICROGRAVITY SIMULATORS. THIS WILL BE.ACCOMPLISHED BY GROWING PLANTS ON CLINOSTATS AND THE RANDOM POSITIONING MACHINE BOTH AT THE.UNIVERSITY OF WISCONSIN-MADISON AND AT KENNEDY SPACE CENTER AND FOLLOWING GROWTH DYNAMICS.AND ACTIN CYTOSKELETON DYNAMICS USING IMAGE ANALYSIS.