My lab focuses on the regulation of organogenesis in plants, using the roots of Arabidopsis thaliana as a model system. Plant root systems are developmentally plastic, and respond to environmental conditions by adding lateral roots to the system at appropriate locations. We characterized lateral root formation in detail, and showed that there are several developmental stages that can be independently regulated in root organogenesis. Our studies defined a putative nitrate transporter as a component of a signaling pathway coordinating lateral root initiation with nutritional cues, demonstrating for the first time that nutrient transporters in plants may have signaling roles independent of nutrient transport. We also identified sugars in the shoot as a critical long-distance regulator of lateral root development post-emergence. This finding suggests that root system development is coordinated with shoot system development via the system movement of sucrose in the phloem. This is consistent with our recent finding that correct development of the phloem and phloem delivery to the root tip is essential for lateral root formation and subsequent growth. Recently, we extended our studies to the process of root and shoot regeneration from cultured root explants. Regeneration originates from the same cells that give rise to lateral roots, and we have demonstrated a role for Polycomb proteins in the ease of trans-differentiation of these root cells to shoot cells.
Roycewicz, P. and Malamy, J.E. (2012) Dissecting the effects of nitrate, sucrose and osmotic potential on Arabidosis root and shoot system growth in laboratory assays. Phil. Trans. Royal. Soc. B. Philos Trans R Soc Lond B Biol Sci. 367(1595):1489-500. (PubMed)
Ingram, P.A., Dettmar, J., Helariutta, Y. and Malamy, J.E. (2011) Arabidopsis Lateral Root Development 3 is essential for early phloem development and function, and hence for normal root system development. Plant Journal 68:455-67. (PubMed)
Macgregor, D.M., Deak, K.I., Ingram, P.A. and Malamy, J.E. (2008) Root architecture in Arabidopsis grown in culture is controlled by sucrose uptake in the aerial tissues. Plant Cell 20, 2643-2660. (PubMed)
Fitz Gerald, J.N., Lehti-Shiu, M.D., Ingram, P.A., Deak, K.I., Biesiada, T., and Malamy, J.E. (2006) Identification of quantitative trait loci that regulate Arabidopsis root system size and plasticity. Genetics 172: 485-498. (PubMed)
Little, D., Rao, H., Oliva, S., Daniel-Vedele, F., Krapp, A., and Malamy, J.E. (2005) The putative high-affinity nitrate transporter NRT2.1 represses lateral root initiation in response to nutritional cues. Proc. Natl. Acad. Sci. USA 102, 13693-13598. (PubMed)
Deak, K.I. and Malamy, J.E. (2005) Osmotic regulation of root system architecture.
Plant J. 43, 17-28. (PubMed)
Nawy, T., Lee, J.Y., Colinas, J., Wang, J.Y., Thongrod, S.C., Malamy J.E., Birnbaum K., and Benfey, P.N. (2005) Transcriptional Profile of the Arabidopsis Root Quiescent Center. Plant Cell 17, 1908-1925. (PubMed)
Malamy, J.E. and Ryan, K.S. (2001) Environmental regulation of lateral root initiation in Arabidopsis thaliana. Plant Physiology 127, 899-909. (PubMed)
Malamy, J.E. and Benfey, P.N. (1997) Analysis of SCARECROW expression using a rapid system for assessing transgene expression in Arabidopsis roots. Plant J. 12, 957-963. (PubMed)
Malamy, J.E. and Benfey, P.N. (1997) Organization and cell differentiation in lateral roots of Arabidopsis thaliana. Development 124, 33-44. (PubMed)