|Navarre, Duroy - Roy|
Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2005
Publication Date: 6/1/2006
Citation: Chandra-Shekara, A.C., Gupte, M., Navarre, D.A., Raina, R., Klessig, D., Kachroo, D. 2006. Light dependent hypersensitive response and resistance signaling against turnip crinkle virus in arabidopsis. Plant Journal. 45:320-334. Interpretive Summary: This work reveals that light is involved in the resistance of plants to viruses. Resistance to TCV OR TMV by Arabidopsis and tobacco respectively is influenced by light. Plants exposed to prolonged darkness prior to inoculation with plant viruses exhibited compromised hypersensitive response, increased lesion size and systemic spread of virus throughout the plant. Thus, a light-mediated pathway appears to play a key role in the generalized scheme of signaling events leading to HR and resistance. Further elucidation of this pathway should facilitate the development of disease resistant plants.
Technical Abstract: Resistance to turnip crinkle virus (TCV) in Arabidopsis ecotype Dijon (Di)-17 is conferred by the resistance gene HRT and a recessive locus rrt. Inoculation of TCV on Di-17 elicits a hypersensitive response (HR), which is accompanied by increased expression of the pathogenesis-related (PR) genes and high levels of salicylic acid (SA). We have previously shown that HRT-mediated resistance to TCV is dependent on SA-pathway and increased levels of SA confer enhanced resistance to TCV via upregulating the HRT gene. Here we show that HRT-mediated HR and resistance are dependent on light. A dark phase, immediately following TCV inoculation, suppresses both HR and resistance and suppresses induction of a majority of TCV-induced genes. However, absence of light does not affect either TCV-induced free SA levels or the expression of HRT. Interestingly, transgenic plants overexpressing HRT showed susceptibility but overexpression of HRT coupled to high levels of endogenous SA showed pronounced resistance in the dark. This was consistent with the observation that exogenous application of SA, in light and prior to TCV inoculation, partially overcomes a requirement for light. Light was also required for HR and resistance against N-gene-mediated HR and resistance to tobacco mosaic virus, suggesting that it is an important factor, which may be universally required during resistance signaling.