Glyphosate Resistance in <i>Eleusine indica</i>: Involvement of <i>CYP71AK44</i> in Addition to <i>EPSPS</i> Gene Overexpression

Intensive application of glyphosate has resulted in resistance evolution in many weed populations, including <i>Eleusine indica</i>. This study characterized glyphosate resistance and investigated the underlying mechanisms in a glyphosate-resistant population (R-JX) of <i>E. indica</i> from China. The R-JX population was 8.5 times resistant to glyphosate relative to the glyphosate-susceptible population (SA). Point mutations were not observed in the target gene 5-enolypyruvyl-shikimate-3-phosphate synthase gene (<i>EPSPS</i>). However, the expression level and copy number of <i>EPSPS</i> were 8.8 times and 15.2 times, respectively, greater in R-JX than that in the SA population. Pre-application of the P450 inhibitor lowered the resistance level to glyphosate from 8.5 times to 3.6 times in the R-JX population. RNA-Seq and RT-qPCR revealed that the <i>CYP71AK44</i> gene was consistently upregulated in R-JX and five other glyphosate-resistant populations. Rice calli and seedlings overexpressing <i>CYP71AK44</i> showed glyphosate resistance. In conclusion, overexpression of the target <i>EPSPS</i> plus <i>CYP71AK44</i> collectively contributes to glyphosate resistance in these <i>E. indica</i> populations.