Unlike the situation seen in animals, much of plant development does not occur in the embryo, but rather, after the seed germinates and continues for the lifetime of the plant. All new growth initially is derived from a special region at the tip of the shoot and root called the meristem. Following elaboration of the primary root, plant root systems enlarge in two ways: first, by growing longer, and second, by forming branch roots, called lateral roots, which grow from the main root. Furthermore, plant roots do not form randomly, but are responsive to differences in the environment and intrinsic factors such as the chemical messengers, or hormones, that coordinate the plant's response. This study examines the effect of a plant hormone, Abscisic Acid (ABA), on the growth of meristems of both primary and lateral roots. Legume roots form an additional structure, a symbiotic root nodule, that results from an interaction with a beneficial bacterium, Rhizobium. The evolutionary origin of these nodules is unknown, but they appear to share some features with lateral roots. This project will examine the role of the M. truncatula LATD gene in the ABA response both in legume lateral roots and in nodules. The aims of the project are to clone and sequence the LATD gene and to determine its role in the ABA response of legume roots and nodules. These findings will lead to increased understanding of plant control of symbiotic nodules, hormone signaling in legumes, and the relationship of nodule formation to growth of the root system.
Broader Impacts: Legumes are an important part of the world's food supply. This project will examine how root system formation in legumes differs from that of other plants and may lead to improved agricultural practices. It will also contribute to the training of a postdoc, graduate student, and undergraduate researchers, as well as continuing outreach activities with a local elementary school, involving plant-based science experiments on root growth and the development of predictions based upon their experiments.
