Abstract
The evolution of herbicide-resistant weed species is a serious threat for weed control. Therefore, we need an improved understanding of how gene regulation confers herbicide resistance in order to slow the evolution of resistance. The present study analyzed differentially expressed genes after glyphosate treatment on a glyphosate-resistant Tennessee ecotype (TNR) of horseweed (Conyza canadensis), compared to a susceptible biotype (TNS). A read size of 100.2 M was sequenced on the Illumina platform and subjected to de novo assembly, resulting in 77,072 gene-level contigs, of which 32,493 were uniquely annotated by a BlastX alignment of protein sequence similarity. The most differentially expressed genes were enriched in the gene ontology (GO) term of the transmembrane transport protein. In addition, fifteen upregulated genes were identified in TNR after glyphosate treatment but were not detected in TNS. Ten of these upregulated genes were transmembrane transporter or kinase receptor proteins. Therefore, a combination of changes in gene expression among transmembrane receptor and kinase receptor proteins may be important for endowing non-target-site glyphosate-resistant C. canadensis.
Highlights
Weeds continue to evolve in agronomic ecosystems, in many cases, to become more weedy and a bane to farmers
The single nucleotide polymorphism or differential gene expression of enolpyruvylshikimate-3-phosphate synthase (EPSPS) has not been detected in two different high-throughput sequencing results of C. bonariensis [13,14]. These results indicated that EPSPS was unlikely to be a player in glyphosate resistance in C. bonariensis
The present study introduces novel differentially expressed genes in glyphosate-resistant and -susceptible C. canadensis biotypes (TN ecotype)
Summary
Weeds continue to evolve in agronomic ecosystems, in many cases, to become more weedy and a bane to farmers. Among the various commercial herbicides, glyphosate has been regarded as an effective chemical herbicide because of its relatively low environmental risk and economic cost [1]. Wide and intensive use of glyphosate has led to the appearance of glyphosate-resistant weeds. Since rigid ryegrass (Lolium rigidum) was reported from Australia as the first glyphosate-resistant weed [4], 38 weed species have evolved resistance to glyphosate worldwide [5]. The appearance of glyphosate-resistance among weeds impacts both weed control costs and crop yields [6]. Among glyphosateresistant weed species, horseweed (Conyza canadensis), and its congener, hairy fleabane (Conyza bonariensis), of the Asteraceae family, are regarded as more troublesome weeds because they have evolved to resist glyphosate [7]
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