**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** THIS PROPOSAL ADDRESSES A MAJOR CHALLENGE THAT CURRENTLY LIMITS THE GROWTH OF LIGNOCELLULOSIC FEEDSTOCK FOR BIOFUEL AND BIOENERGY. SPECIFICALLY, LIGNOCELLULOSIC BIOENERGY CROPS ARE INTENDED TO BE GROWN ON MARGINAL LANDS, WHERE POOR, INTERMITTENT, AND/OR SPATIALLY HETEROGENEOUS RESOURCES CAN COMPROMISE FEEDSTOCK YIELD AND QUALITY. NITROGEN IS A MAJOR FACTOR THAT LIMITS YIELD AND DEGRADES FEEDSTOCK QUALITY ON MARGINAL LANDS. THEREFORE, SUCCESSFUL AND EFFICIENT CULTIVATION OF BIOENERGY CROPS ON MARGINAL LANDS WILL ENTAIL DEVELOPING VARIETIES THAT CAN SUSTAIN HIGH BIOMASS YIELD AND QUALITY UNDER A BROAD RANGE OF NITROGEN CONDITIONS.IMPROVING BIOMASS PRODUCTIVITY UNDER LOW NITROGEN CONDITIONS HAS PROVEN TO BE A DIFFICULT TASK. THIS IS MAINLY DUE TO THE COMPLEXITY OF THE RESPONSES TO NITROGEN, WHICH INVOLVES VARIOUS TISSUES, ORGANS, AND PROCESSES. COORDINATION OF THESE MULTIPLE LEVELS OF RESPONSE IS CHALLENGING. USING ACTIVATION TAGGING WE HAVE DISCOVERED THE POPLAR RED NAC (RN) TRANSCRIPTION FACTOR (TF) THAT COORDINATELY REGULATES SEVERAL OF THESE RESPONSES. THIS PROPOSAL AIMS TO:1. ELUCIDATE THE MECHANISMS UNDERLYING RN-REGULATED PROCESSES USING MOLECULAR APPROACHES THAT CAN UNRAVEL THE FINE SCALE OF THE RN-ASSOCIATED MECHANISM.2. UNDERSTAND THE CONTEXT OF RN FUNCTION AT THE ORGAN AND ORGANISMAL LEVEL USING RECIPROCAL GRAFTING AND PHYSIOLOGICAL APPROACHES.3. CHARACTERIZE THE FIELD PERFORMANCE OF RN-MODIFIED TRANSGENICS IN A MULTI-YEAR FIELD TRIAL.THE KNOWLEDGE THAT THIS PROPOSAL GENERATES CAN SIGNIFICANTLY CONTRIBUTE TO TECHNOLOGICAL INNOVATIONS ENABLING TOOLS FOR MANIPULATION OF BIOMASS PRODUCTIVITY UNDER LOW NITROGEN CONDITIONS IN BIOENERGY AND AGRICULTURAL CROPS.