ARS | Publication request: Constitutive expression of viral suppressors of PTGS in sugarcane

Submitted to: Plant and Animal Genome Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: October 1, 2006
Publication Date: N/A

Technical Abstract: In our experience, transgenes are silenced by sugarcane at a high frequency. In many cases the silencing is via posttranscriptional gene silencing (PTGS). To understand more about PTGS in sugarcane we are studying the P0 protein of Sugarcane yellow leaf virus (SCYLV) which acts to suppress PTGS. One possible application of SCYLV P0 or other viral suppressors of PTGS would be to control transgene silencing. However, since PTGS can be critical to several important plant functions including regulation of endogenous genes, expression of viral suppressors may produce unacceptable side effects in transgenic plants. To explore these possibilities, we produced sugarcane transgenic lines which constitutively express one of four viral PTGS suppressors: SCYLV P0, HC-Pro from Sorghum mosaic virus, p25 from Potato virus X, and p38 from Turnip crinkle virus. Expression data from P0 and HC-Pro transgenic plants showed that those lines with the highest mRNA accumulation for an nptII transgene also had high levels of the suppressor mRNA. Expression of five sugarcane genes predicted to be regulated by miRNAs (Jones-Rhoades, et al.) was tested by qRT-PCR. For all five of these genes there were no consistent differences in HcPro transgenic lines as compared to WT sugarcane. For one of the miRNA-regulated genes, differences were observed in P0-expressing lines; however these differences do not correspond to expression levels of P0. This suggests the variation in endogenous gene expression is caused by other factors. Morphologically some suppressor lines are abnormal, but the frequency of these changes is similar for other (not expressing suppressors) sugarcane regenerated from tissue culture.