Transgenic Expression Of A Functional Fragment Of Harpin Protein HPA1 In Wheat Induces The Phloem-Based Defense To English Grain Aphid

As one of the most important staple crop, wheat is grown in about 40 countries around the world. With the world economy and the rapid growth of the population, we need to increase the production of the wheat. But there are various factors seriously affected the yield and quality of wheat, such as adverse environmental conditions, plant diseases and insect pests. Aphids are the important pests on wheat crops, which not only can injure wheat leaves, stems and the tender ears that can affect the growth and yield of wheat, but also can spread a variety of virus disease, causing severe damage to wheat.According to previous studies, HrpNEa is a multifunctional elicitor, stimulating different signaling pathways and also inducing the hypersensitive cell death and resistance to pathogens and insects. In this research, we obtained the transgenic Hpal 10-42 wheat. We studied the effects of the expression of Hpal 10-42 to English grain aphid and discussed the signal pathways involved into. 1A Hpal fragment induces resistance to aphids in wheatIn this experiment, we got six transgenic wheat (#1-#6) and studied the phloem defense to English grain aphid. According to the results, the expression of Hpal10-42 can reduce the aphid colonization. We also tested the expression of PP2-A and GSL. We found that the expression of PP2-A and three GSL(GSL2, GSL10, GSL12) were higher when a small amount of aphids feeding on. We also analyzed the feeding activities of aphids and callose deposition. According to the EPG monitoring for six hours, the time that aphids feeding on transgenic wheat was shorter when compared with control. Also the proportions of closed sieve plate pores were significantly greater in Y16:Hpal10-42 lines than in the Y16 plant. We also found the Hpal10-42 expression increases grain yield of wheat in the presence of a small amount of aphid infestation. 2 Hpal10-42-induced phloem-based defense is regulated by ethylene signalingAs a multiple functional elicitor, HrpNEa can stimulate different signaling pathways. According to the this study, the expression of Hpal 10-42 can activated the ethylene signal pathway, indicating that EIN2 participated in the phloem-based defense. We found the higher expression of EIN2, PP2-A and GSL10 in transgenic wheat, but they are lower when the ethylene signaling inhibitor AgNO3 or 1-MCP used. The feeding time of phloem was longer and the proportions of closed sieve plate pores were lower when the ethylene signaling inhibitor used. It proved that ethylene signaling participated in the regulation of phloem-based defense. We also found an interesting phenomenon that the total length of root is longer and the branches of root are higher, it may be referred to the regulation of ethylene signaling.Summary remarksThe transgenic Hpal 10-42 wheat was first obtained, and we discussed the expression of Hpal 10-42 whether can affect the feeding activities. The mechanism of phloem-based defense was also discussed. All that can help us to research the molecular mechanisms of aphid resistance and get the higher yield of wheat.