Jocelyn E. Malamy

Plant root systems are developmentally plastic, and respond to environmental conditions by adding lateral roots to the system where and when they are needed. Using the model plant Arabidopsis, we characterized root system responses to various growth conditions, and demonstrated that lateral root formation is strongly repressed by osmotica and specific combinations of nutrients. The osmotic and nutrient cues used in our assays must trigger different signaling mechanisms in the root system, as one represses lateral root initiation while the other targets a later stage in lateral root formation. Forward and reverse genetic screens, expression profiling and quantitative genetic analyses based on both assays lead to identification of novel signaling pathways that are critical for the regulation of root system morphology. For example, 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 (Little et al., 2005). Analysis of natural variation in root system morphology identified QTLs that regulate intrinsic lateral root development programs (FitzGerald et al., 2006). Characterization of another mutant lead us to identify sucrose as a key regulator of lateral root formation (Macgregor et al., submitted). In the upcoming years, my lab will continue to focus on the signaling pathways that regulate of lateral root formation and its modulation by environmental cues. We will also apply our knowledge to agricultural problems, as the architecture of the root system determines the ability of many crop plants to survive harsh conditions such as water and nutrient stress.

Plant root systems are developmentally plastic, and respond to environmental conditions by adding lateral roots to the system where and when they are needed. Using the model plant Arabidopsis, we characterized root system responses to various growth conditions, and demonstrated that lateral root formation is strongly repressed by osmotica and specific combinations of nutrients. The osmotic and nutrient cues used in our assays must trigger different signaling mechanisms in the root system, as one represses lateral root initiation while the other targets a later stage in lateral root formation. Forward and reverse genetic screens, expression profiling and quantitative genetic analyses based on both assays lead to identification of novel signaling pathways that are critical for the regulation of root system morphology. For example, 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 (Little et al., 2005). Analysis of natural variation in root system morphology identified QTLs that regulate intrinsic lateral root development programs (FitzGerald et al., 2006). Characterization of another mutant lead us to identify...

Root system architecture in Arabidopsis grown in culture is regulated by sucrose uptake in the aerial tissues. Macgregor DR, Deak KI, Ingram PA, Malamy JE. (2008) Plant Cell. 20:2643-60.  

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. 

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. 

Deak, K.I. and Malamy, J.E. (2005) Osmotic regulation of root system architecture. Plant J. 43, 17-28  

Malamy, J. (2005) Intrinsic and environmental factors regulating root system growth. Plant, Cell and Env. 28, 67-77. 

Malamy, J. E. and Ryan, K. S. (2001). "Environmental regulation of lateral root initiation in Arabidopsis." Plant Physiol 127: 899-909.   PubMed Citation

Wysocka-Diller, J. W., Helariutta, Y., Fukaki, H., Malamy, J. E. and Benfey, P. N. (2000). "Molecular analysis of SCARECROW function reveals a radial patterning mechanism common to root and shoot." Development 127: 595-603.   PubMed Citation

Malamy, J. and Benfey, P. (1997) Down and out in Arabidopsis: lateral root formation. Trends in Plant Sci. 2: 390-396. 

Malamy, J. and Benfey, P. (1997) Organization and cell differentiation in lateral roots of Arabidopsis thaliana. Development 124: 33-44.  

Root system architecture in Arabidopsis grown in culture is regulated by sucrose uptake in the aerial tissues. Macgregor DR, Deak KI, Ingram PA, Malamy JE. (2008) Plant Cell. 20:2643-60.  

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. 

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. 

Deak, K.I. and Malamy, J.E. (2005) Osmotic regulation of root system architecture. Plant J. 43, 17-28  

Malamy, J. (2005) Intrinsic and environmental factors regulating root system growth. Plant, Cell and Env. 28, 67-77.