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Transcriptomic analysis reveals the transcription factors involved in regulating the expression of EPSPS gene, which confers glyphosate resistance of goosegrass (Eleusine indica)
ZHANG Chun, YU Chao-jie, ZHANG Tai-jie, GUO Wen-lei, TIAN Xing-shan
2021, 20 (8): 2180-2194.   DOI: 10.1016/S2095-3119(21)63682-1
Abstract169)      PDF in ScienceDirect      
Glyphosate inhibits the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) and overexpression of the EPSPS gene is one of the molecular mechanisms conferring glyphosate resistance in weeds.  A regulatory sequence of EPSPS gene was isolated previously, and an alteration in its 5´-untranslated region (UTR) pyrimidine (Py)-rich stretch element is involved in the regulation of EPSPS expression in glyphosate-resistant (GR) Eleusine indica.  However, the transcription factors involved in this regulatory sequence remain to be elucidated.  In this study, we investigated the regulatory network of EPSPS overexpression associated genes in a GR E. indica population by RNA-seq.  The differentially expressed transcript analyses revealed that glyphosate treatment caused an increase in the expression of 2 752 unigenes and a decrease in the expression of 4 025 unigenes in the GR E. indica, compared to the glyphosate-susceptible (GS) E. indica.  Among them, 1 373 unigenes were identified to be co-expressed with the EPSPS gene in GR E. indica.  GO and KEGG pathway analyses showed that the up-regulated unigenes were mainly enriched in chloroplasts and associated with the shikimate biosynthesis pathway, chlorophy II and peroxisome metabolism processes.  Notably, the expression of a Shikimate kinase which catalyzed the conversion of Shikimate to Shikimate 3-phosphate (S3P, a substrate of EPSPS), was also up-regulated.  Eight transcription factors were identified as likely to be involved in the regulation of the EPSPS expression, and three of them (ARF2, ARF8 and BPC6) showed more binding sites because of a (CT)n insertion of the 5´-UTR Py-rich stretch element in GR.  However, the yeast one-hybrid assay illustrated that ARF8 and BPC6 could bind to the 5´-UTR Py-rich stretch element of wild type EPSPS, but could not bind to the mutated form.  Our data suggests that the transcriptional regulation of EPSPS expression is complex and was significantly altered in GR E. indica.  These discoveries provide new references for further study of the EPSPS overexpression mechanism that endows glyphosate resistance. 
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Alleles contributing to acetyl coenzyme A carboxylase (ACCase) resistance in keng stiffgrass (Pseudosclerochloa kengiana) populations from China
YUAN Guo-hui, GUO Wen-lei, DU Long, LIU Wei-tang, LI Qi, LI Ling-xu, WANG Jin-xin
2017, 16 (01): 125-134.   DOI: 10.1016/S2095-3119(16)61452-1
Abstract666)      PDF in ScienceDirect      
Keng stiffgrass is a grass weed that affects wheat-rice cropping systems in China.  The extensive reliance on acetyl coenzyme A carboxylase (ACCase)-inhibiting herbicides has resulted in keng stiffgrass developing resistance to these herbicides.  The objective of this research was to evaluate the resistance level of the putative resistant keng stiffgrass populations to ACCase-inhibiting herbicides and to identify their molecular resistance mechanism.  Whole-plant dose-response experiments demonstrated that SD-4 (R), SD-11 (R), and JS-25 (R) populations were highly resistant to fenoxaprop, clodinafop, and fluazifop, moderately resistant to diclofop, had low resistance to sethoxydim and pinoxaden, but were sensitive to clethodim.  Partial chloroplastic ACCase sequences showed that there were two copies of ACCase gene in keng stiffgrass, and all homoeologous genes were expressed.  The results of sequence analyses of the ACCase CT domain revealed an isoleucine-to-asparagine substitution at position 2041 in SD-4 (R) and SD-11 (R) populations, and a tryptophan-to-cysteine substitution at position 2027 in the JS-25 (R) population.  To our knowledge, this is the first report of Ile-2041-Asn and Trp-2027-Cys mutations in ACCase-resistant keng stiffgrass.  In addition, three robust (derived) cleaved amplified polymorphic sequence ((d)CAPS) markers have been developed to rapidly identify these mutations in the ACCase gene of keng stiffgrass.
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