Venugopal, Srivathsa , Chandra-Shekara, AC , Roy Barman, Subhankar , Kachroo, Aardra , Kachroo, Pradeep .
Plastidial oleic acid levels modulate defense signaling by regulating expression of resistance genes.
Oleic acid (18:1) is one of the major monounsaturated fatty acids of membrane glycerolipids and its biosynthesis is catalyzed by the soluble stearoyl-acyl-carrier-protein-desaturase (S-ACP-DES). We have previously shown that changes in the levels of 18:1 results in the alteration of salicylic acid- and jasmonic acid-mediated defense responses (1-3). This is evident in the Arabidopsis ssi2 mutant, which encodes a defective S-ACP-DES and consequently accumulates low levels of 18:1. Replenishing 18:1 levels results in restoration of wild-type-like signaling in the ssi2 mutant (1-4). Plants carrying low levels of 18:1 exhibit enhanced resistance to virulent pathogens, as well as R-gene specific resistance to viral (Turnip crinkle virus-TCV) and bacterial pathogens (5-6). The18:1-mediated signaling modulates defense by upregulating expression of multiple R genes (6). Normalizing 18:1 levels by second-site mutations restores R gene expression and pathogen resistance. Intriguingly, TCV inoculation does not activate the 18:1-regulated pathway in resistant plants, instead it results in the induction of several genes that encode 18:1-synthesizing isozymes. Consequently 18:1 levels in the plant remain constant during a resistance response to TCV. These data suggest that the 18:1-regulated pathway may be specifically targeted during pathogen infection and that alterations of 18:1 levels may serve as a novel strategy for promoting disease resistance.
1. Kachroo et al., (2003) Plant Cell 15, 2952
2. Kachroo et al., (2004) PNAS 101, 5152
3. Kachroo et al., (2005) Plant Physiol., 139, 1717
4. Kachroo et al., (2007) PMB, 63, 257
5. Chandra-Shekara et al., (2004) Plant J. 40, 647
6. Chandra-Shekara et al., (2007) PNAS, In press
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Pradeep Kachroo's lab
1 - University of Kentucky, Plant Pathology, Lexington, KY, 40546
2 - (Current Address) BioDiagnostics, River Falls, WI, 54022
Turnip Crinkle Virus
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM