During the evolution of complex biological organisms important events occurred that led to the integration of physiological and developmental processes at the organismal level. An important component here was the origin of signaling networks that recognize and transmit information relating to environmental inputs. For example, in the plant kingdom, a signaling system evolved to coordinate floral induction with the environmental input of day length. In this project, experiments will be performed to develop a more detailed understanding of the molecules that move through the plant?s vascular system to transmit the florigenic signal that reprograms the shoot apical meristem into an inflorescence meristem, which then proceeds to form flowers. These studies will involve a range of experimental techniques and will require an integration of project objectives from the biochemical and molecular to the cellular, physiological, genetic and whole-plant levels. The project will address the following specific objectives: (a) elucidate the mechanism by which FLOWERING LOCUS T (FT), the florigenic signaling molecule, enters the vascular system, (b) establish the controls that operate to ensure delivery of FT to apical tissues where flowers can be formed and (c) investigate the mechanism(s) that controls the delivery of FT to these target tissues. Development of a comprehensive understanding of the molecular events that operate to control the long-distance transmission of FT will advance our understanding of the principles for inter-organ signaling through the plant?s non-circulatory vascular system. The Broader Impacts of the project are as follows. The knowledge generated from the project should provide a foundation for the discovery and characterization of additional proteins that serve as long-distance signaling agents for other abiotic and biotic inputs. In addition, flowering plants serve as a major component of the world?s food source. In terms of societal benefits, new insights into the florigenic signaling network should lead to the development of crops having novel control over flowering. Finally, the junior scientists who will receive training under this project will serve as a cadre of trained experts to contribute to the further discovery of long-distance signaling molecules. Such systems could be involved in plant defense and nutrient acquisition; control over these processes will contribute to world food security.
Modern agriculture is geared towards the production of food, fiber and renewable energy. To ensure food security for a projected 9 billion global inhabitants, the plant biology community is faced with the challenge of increasing yields for such staple crops as corn, rice, wheat, etc. These grains, along with the fruits that provide basic nutritional needs essential for human health and wellbeing, are the products of flowers. Thus, to achieve the goal of food security it is fundamentally important that the scientific community develops a thorough understanding of the mechanism(s) employed by plants to regulate floral development. Many plant species utilize day length as an environmental input to control the signaling processes that regulate when flowers are produced. In these plants, a mobile signal, termed ‘florigen,’ is generated within the leaves that perceive this day length or photoperiodic input signal. Florigen was recently identified to be a small protein that moves through the plant vascular system and, upon its entry into the plant apex, functions to reprogram the cells of the apex to generate floral organs. With support provided by this NSF grant, we have used a combination of approaches, including genetics, genomics, molecular, cellular and biochemical methods to investigate the molecular machinery employed by the plant to deliver this long-distance signaling florigenic protein. Novel insights afforded by this research can be used to engineer control over the timing of floral initiation with the goal of enhancing the yield potential of a wide range of crop species.
