UMBC An Honors University in Maryland
UMBC Biological Sciences
Contact Information

Location: BS 415
Phone: 410-455-5972

Location: BS 411/412
Phone: 410-455-2263

Projects
Lu Group
Investigating mechanisms of disease resistance in Arabidopsis thaliana

Upon pathogen infection, plants activate an array of defense responses, including reprogramming the expression of thousands of genes. However, a major challenge in the field is to determine which genes regulate defense as opposed to being diagnostic for infection. In order to discover novel defense genes, we performed a high throughput genetic screen, based on the unique Arabidopsis mutant called accelerated cell death 6-1 (acd6-1). ACD6 encodes a membrane protein with ankyrin repeats and was shown to be a major determinant of fitness in Arabidopsis (Lu et al., 2003; Todesco et al.). acd6-1 is a gain-of-function mutant that demonstrates constitutive defense, severe cell death, and extreme dwarfism and accumulates high levels of salicylic acid (SA), the key defense signaling molecule (Rate et al., 1999; Lu et al., 2003). Interestingly, second site mutations disrupting SA accumulation and/or SA signaling suppress the small size of acd6-1, suggesting that acd6-1-conferred dwarfism is inversely correlated with its defense levels (Lu et al., 2009). Therefore, the size change of acd6-1 can be used as a convenient readout in a large-scale screen of acd6-1 suppressors (sups), which may harbor mutations disrupting important defense genes. In addition, we have also exploited this unique feature of acd6-1 in elucidating functional relationships among components in defense signaling networks (Ng et al., 2011).

Figure panel A: ACD6 protein structure and the acd6-1 mutant.

Figure panel B: the size of acd6-1 is sensitized to the change of defense levels. 


Selected references
  1. Lu, H., Rate, D.N., Song, J.T., and Greenberg, J.T. (2003). ACD6, a novel ankyrin protein, is a regulator and an effector of salicylic acid signaling in the Arabidopsis defense response. Plant Cell 15, 2408-2420.
  2. Lu, H., Salimian, S., Gamelin, E., Wang, G., Fedorowski, J., LaCourse, W., and Greenberg, J.T. (2009). Genetic analysis of acd6-1 reveals complex defense networks and leads to identification of novel defense genes in Arabidopsis. Plant J 58, 401-412.
  3. Ng, G., Seabolt, S., Zhang, C., Salimian, S., Watkins, T.A., and Lu, H. (2011). Genetic dissection of salicylic acid-mediated defense signaling networks in Arabidopsis. Genetics, in press.
  4. Rate, D.N., Cuenca, J.V., Bowman, G.R., Guttman, D.S., and Greenberg, J.T. (1999). The gain-of-function Arabidopsis acd6 mutant reveals novel regulation and function of the salicylic acid signaling pathway in controlling cell death, defenses, and cell growth. Plant Cell 11, 1695-1708.
  5. Todesco, M., Balasubramanian, S., Hu, T.T., Traw, M.B., Horton, M., Epple, P., Kuhns, C., Sureshkumar, S., Schwartz, C., Lanz, C., Laitinen, R.A., Huang, Y., Chory, J., Lipka, V., Borevitz, J.O., Dangl, J.L., Bergelson, J., Nordborg, M., and Weigel, D. (2010). Natural allelic variation underlying a major fitness trade-off in Arabidopsis thaliana. Nature 465, 632-636.