GmERF54, an ERF Transcription Factor, Negatively Regulates the Resistance of Soybean to the Common Cutworm (Spodoptera litura Fabricius)

Soybean is attacked by various herbivorous insect pest species during the whole course of its life cycle in the field. It is important for soybean production to improve insect resistance by identifying and utilizing soybean endogenous insect-resistant genes. The ethylene-responsive transcription factor (ERF) plays a significant role in plant biotic and abiotic stresses; however, few studies focus on its role in insect resistance in soybean. Here, based on our previous common cutworm (CCW)-induced soybean transcriptome data, a soybean ERF gene GmERF54 was cloned, which responded to CCW feeding. Transcriptional analysis revealed that GmERF54 was ubiquitous in all soybean tissues and was expressed differently in insect-resistant and insect-susceptible soybean cultivars. RNA interference of GmERF54 increased the resistance to CCW, while the overexpression of GmERF54 decreased the resistance to CCW in transgenic soybean hairy roots compared with their controls. GmERF54 was localized to the nucleus, had transcriptional activation activity, and interacted with AP2/ERF GmPLT2. Several putative hormone response elements were predicted in the promoter sequence of GmERF54. Four putative elements were only found in the GmERF54 promoter sequence of insect-resistant cultivar Wanxianbaidongdou (WX), but not in the insect-susceptible cultivar Nannong 99-10 (99-10). GmERF54 promoter sequences of WX and 99-10 were cloned into the pCAMBIA1381z vector containing the beta-glucuronidase (GUS) gene to generate GmERF54(WX):GUS and GmERF54(99-10):GUS recombinant vectors, respectively. GUS staining of soybean hairy roots containing GmERF54(WX):GUS and GmERF54(99-10):GUS showed that GmERF54 was induced by CCW attack and both MeJA (methyl jasmonate) and IAA (indole-3-acetic acid) treatments. Alleles in insect-resistant and insect-sensitive cultivars responded to these inductions differently. Overall, our results reveal that GmERF54 may be involved in the regulation of soybean resistance to CCW.