Submitted to: International Journal of Plant Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 25, 2009
Publication Date: October 1, 2009
Citation: Kuykendall, L.D., Shao, J.Y., Trimmer, K.A. 2009. A nest of LTR retrotransposons adjacent the disease resistance-priming gene NPR1 in Beta vulgaris L. U.S. Hybrid H20. International Journal of Plant Genomics. 2009: Article ID 576742, 8 pages.
Interpretive Summary: New strategies for improving disease resistance, an agricultural trait of tremendous importance to profitability and sustainability, are being developed using results of plant genomics research. Scientists in the Molecular Plant Pathology Laboratory discovered two mobile genetic elements (MGEs) closely located near the disease resistance-priming gene NPR1 in sugar beet. MGEs may also control or negatively or positively influence the expression of nearby genes. Molecular genetics studies show that the two MGEs discovered in sugar beet are nearly identical to MGEs in cucumber, rice and sorghum. This information will contribute to developing genome manipulation technology using mobile DNA elements to improve plant disease resistance in various agricultural crops. It is very likely, therefore, that the discovery of MGEs that are very physically close to the disease resistance-priming gene will be useful to other plant molecular biologists working to improve disease resistance.
LTR_STRUC and LTR FINDER analyses of a sugar beet BAC, with the NPR1 disease resistance priming gene, identified two distinct LTR (long terminal repeats) retrotransposons. BvRTR1 has two ORFs: one encoding a Ty1/copia-like integrase and the other a hypothetical gene. RTR1 is 10,833 bp in length including 1,372 bp LTRs that share 99.3% identity. Based on BLASTn results, RTR1 shares about 98% nucleotide sequence identity with about 11 Kb DNA total from two fragments (DQ324026 and DQ374025) from BAC62, subcloned from Beta vulgaris chromosome 9. BvRTR2, another LTR retrotransposon identified in this study, encodes a complete and presumably active Ty3-gypsy-class polyprotein, as a single ORF with no introns. RTR2 has 2,561 bp LTR sequences with 100% identity, and about 10% of the 3’ end of the RTR2 LTRs aligned with 97% identity to pDVR2, belonging to a family of recognized Beta vulgaris repeated DNA sequences known to be dispersed over all 18 chromosomes.