LAUSR

BACKGROUND Tubulin, the target site of dinitroaniline herbicides, is encoded by small gene families in plants. To better characterize the target-site resistance mechanisms to dinitroaniline herbicides in the globally important weedy species Lolium rigidum, attempts to amplify and sequence α-tubulin transcripts were made. RESULTS Four α-tubulin isoforms (TUA1, TUA2, TUA3 and TUA4) were identified in L. rigidum. Variations in numbers and sequences of transcripts encoding these α-tubulin proteins were found in individuals of the two L. rigidum populations examined. Within and among populations, differences in 5' and 3' untranslated region of cDNA in TUA3 and TUA4 were identified. Furthermore, a novel double mutation, Arg-390-Cys+Asp-442-Glu, in the TUA3 transcript was identified that has the potential to confer dinitroaniline resistance. CONCLUSION This research reveals the complexity of the α-tubulin gene family in individuals/populations of cross-pollinated weedy species L. rigidum, and highlights the need for a better understanding of the molecular architecture of tubulin gene families for detecting resistance point mutations. Although TUA4 is the commonly expressed α-tubulin isoform containing most frequently reported resistance mutations, other mutant tubulin isoforms may also play a role in conferring dinitroaniline resistance. This article is protected by copyright. All rights reserved.