Working group session:
Functional Genomics
Presentation type:
oral
Authors:
Tuttle, John; Robertson, Dominique; Haigler, Candace
Presenter:
Tuttle, John
Correspondent:
Tuttle, John
Abstract:
A virus-induced gene silencing (VIGS) system developed from the Cotton leaf crumple geminivirus (CLCrV) is effective in vegetative cotton tissues, but it had not been tested in the most economically important part of the plant—cotton fiber. A CLCrV:GFP reporter construct revealed GFP fluorescence in the ovule vasculature but not the fiber. This raised the possibility that the CLCrV-derived silencing signal might not be expressed in cotton fiber, making fiber gene silencing dependent on translocation of siRNAs from adjacent tissues. To test this possibility, we inoculated a cotton line expressing 35S:GFP with CLCrV:GFP and showed that GFP fluorescence was reduced in the fiber from 7 to 20 days post anthesis (DPA). Unlike sectored vegetative silencing, GFP silencing within locules appeared uniform and was correlated with silencing in the adjacent boll wall. Reduced GFP transcript was verified by qRT-PCR at 12, 15, and 20 DPA. Since transgenes are typically more easily silenced, the CLCrV-VIGS system was also used to silence the endogenous cell wall loosening gene, α-expansin1 (GhEXP1), resulting in 8.8% shorter fiber compared to controls. Analysis by qRT-PCR showed reduced GhEXP1 transcript at 16 DPA but not at 12 DPA. Since cotton fibers are symplastically isolated at about 10 to 15 DPA, CLCrV-VIGS of endogenous genes may be hindered during this period. Characterizing the silencing dynamics in this economically important plant cell provides a guide for future VIGS experiments in cotton fiber. For research support we thank NSF (Grant # IOS1025947) and Cotton Inc. (Cary, NC).