Research Summary:
We are studying how the stimuli of light and gravity alter patterns of plant development. In our studies of light-induced responses we have found that ectoapyrase, an enzyme whose expression is strongly regulated by the photoreceptor phytochrome, can modulate the levels of extracellular ATP [eATP], and that, surprisingly, changes in [eATP] can influence hormone transport, the growth of plant cells and organs (including pollen tubes, root hairs, hypocotyls, roots and leaves), wound responses, and toxin resistance in Arabidopsis and other plants. This indicates that eATP, which is a physiological regulator in animals, also influences plant growth and development, and we are investigating how this happens. For our gravitational studies we are using two model systems, Arabidopsis and spores of the fern Ceratopteris richardii. In Arabidopsis we are using genetic approaches to evaluate the role of annexins, which mediate the secretion of wall materials to growing points of cells, in gravitropic growth. In Ceratopteris spores, where gravity directs polarity development, we are using microarrays to compare the pattern of gene expression in space-flown vs. earth-grown cells, so as to identify genes needed for early stages of the spore’s graviresponse, and we using a Micro-Electro-Mechanical system (MEMS) to document very rapid changes in the transport activity of calcium channels and pumps that are directed by gravity.