Year of Publication
Doctor of Philosophy (PhD)
Dr. Pradeep Kachroo
Infection of the resistant Arabidopsis ecotype Di-17 with Turnip Crinkle Virus (TCV) elicits hypersensitive response (HR), accompanied by increased expression of defense genes. HR to TCV is conferred by HRT, which encodes a coiled-coil (CC)-nucleotide-binding site (NBS)-leucine-rich repeat (LRR) class of resistance (R) protein. In contrast to HR, resistance requires HRT and a recessive locus designated rrt. Unlike most CC-NBS-LRR R proteins, HRT-mediated resistance is dependent on EDS1 and independent of NDR1. Resistance is also dependent on salicylic acid (SA) pathway and light. A dark treatment, immediately following TCV inoculation, suppresses HR, resistance and activation of a majority of the TCV-induced genes. To determine the genetic, molecular and biochemical basis of light-dependent defense pathway, we studied the role of various photoreceptors in HRT-mediated resistance to TCV, HRT protein levels and its localization. Interestingly, mutation in blue-light photoreceptors led to degradation of HRT via a proteasome-dependent pathway and resulted in susceptibility to TCV. Exogenous application of SA induced transcription of HRT, which restored HRT levels in some, but not all, mutant backgrounds. These results show that different photoreceptors function distinctly in maintaining post-transcriptional stability of HRT. In addition to photoreceptors, HRT also forms a complex with several other proteins, many of which participate in the RNA silencing pathway and are required for HRT-mediated resistance. Together, our results suggest that HRT forms a multi-protein complex and that HRT-mediated signaling involves reconstitution of this complex.
Jeong, Rae-Dong, "MOLECULAR, GENETIC AND BIOCHEMICAL CHARACTERIZATION OF RESISTANCE PROTEIN-MEDIATED SIGNALING AGAINST TURNIP CRINKLE VIRUS" (2011). University of Kentucky Doctoral Dissertations. 181.