Nanoselenium Enhanced Wheat Resistance to Aphids by Regulating Biosynthesis of DIMBOA and Volatile Components

12 Aphids are one of the most destructive insects in many cultivated plants including 13 wheat, which can cause significant yield loss and damage the quality of agricultural 14 products. Therefore, it is essential to control the occurrence of aphids during wheat 15 growth. Previous studies reported the alterations in the resistance of wheat to pests induced by several external factors such as nutrients in soils and nano-carbonaceous 17 materials. In this study, nanoselenium (nano-Se) was sprayed on wheat leaves at 18 several concentration levels (1.0, 5.0, and 20 mg/L). Nano-Se (5.0 mg/L) could 19 significantly reduce Sitobion avenae number (36%) compared with the control. The 20 foliar application of nano-Se was found to enhance the antioxidation capacity by 21 reducing MDA concentration and increasing GSH-Px, CAT, GSH, Pro and VE 22 concentrations. Phenylpropane pathway was activated after the application of nano- 23 Se, with significantly increasing apigenin and caffeic acid concentrations. The high- 24 level expression of the related genes ( TaBx1A , TaBx3A , TaBx4A, TaASMT2, and 25 TaCOMT ) induced the increasing melatonin concentration by 88.6% and DIMBOA 26 concentration by 64.3%. Different ratios of the secondary metabolites to nano-Se 27 were conducted to examine the effects on wheat resistance to the Sitobion avenae . 28 The results revealed the combination of nano-Se and melatonin can achieve the best 29 overall performance by reducing the Sitobion avenae infection by 52.2%. The results 30 from this study suggest that the coordinative applications nano-Se and melatonin 31 combination could be more effectively improve the wheat resistance to aphids via 32 promotion of volatile organic compound synthesis and modulation in phenylpropane 33 and indole metabolism pathways.


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Wheat (Triticum aestivum L.) is one of the most widely grown grain crops in the 39 world. It could be vulnerably attacked by various herbivores during the process of 40 growth. Aphids are common agricultural spines suck pests, which have a relatively 41 short reproduction cycle hence large population. They directly ingest the nutrients 42 present in plant phloem screen, and can act as the transmission vector of plant viral 43 diseases [1]. These activities can seriously affect the crop yields and the quality of 44 grains [2]. Pesticides are the most widely used to control aphids; however, the overuse 45 of chemical pesticides could lead to potential environmental contamination and 46 damage ecosystem services [3]. Integrated pest management has been strategically 47 adopted to control aphids with biological controls including insect-resistant varieties, 48 crop rotation [4], natural enemy [5], and RNA interference, in many cases they fail to 49 achieve satisfactory performance due primarily to short persistence and high costs [6]. 50 Therefore, it is urgent to develop green, safe, and ecologically reasonable methods for 51 the prevention and control of aphids. Sitobion avenae F and beetles [9]. Many allelopathic substances such as 2,4-59 dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) is commonly found in 60 wheat, corn, and other gramineous crops in response to environmental changes [10]. Helicoverpa armigera growth in tomato plants [14]. 70 Selenium is the main component in the antioxidant enzyme glutathione 71 peroxidase (GSH-Px) and plays an important role in oxidative defense [15]. Zhang  This study aimed to investigate the potential mechanism of the enhanced 108 resistance of wheat to aphids after foliar application of nano-Se. Changes in 109 antioxidant ability and the concentration of flavonoids, phenolic compounds, 110 phytohormone and VOCs were measured in the wheat seedlings. The optimal 111 proportions and composition of these metabolites, as well as the amount of nano-Se 112 application, were examined based on the defense of wheat plants to Sitobion avenae. 113 It is concluded that the combination of nano-Se and melatonin could be involved in 114 the resistance mechanism mainly by regulating the VOCs, phenylpropane, and indoles 115 alkaloid pathways.

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The nano-Se (50-78 nm) applied in this study was characterized and reported in our 127 previous study [31]. The plant experiment was separated into four groups including 128 three levels of nano-Se treatment (5, 10, and 20mg/L) and the controls. These four 129 treatments each had five duplicates.     Table S1. quadrupole). Acetonitrile and formic acid water (contain 1% formic acid) were used as 183 mobile phases A and B for isocratic elution, respectively. The injection volume was 5μL 184 and the flow rate was 0.2 mL/min. Other optimized information was applied in Table   185 S1.

Analysis of flavonoids and phenolic acid compounds 187
Briefly [31], wheat leaves (100mg) were ground to the powder in liquid nitrogen.

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They were added 1mL water (containing 60% ethanol) in a centrifuge tube. The solution 189 was used ultrasound for 30min at 30℃ and then centrifuged for 5min at 12000rpm. The  Table S2 and Table S3.  The inhibitory effects of nano-Se on S. avenae growth are presented in Table 1. As can be seen in Figure 6A, four kinds of samples can separate. There was a 307 significant difference among the four treatments based on the results of fingerprint 308 similarity analysis, and collaboration of Se and MT was the greatest.

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For convenient comparison, the top view is shown in Figure 6B Figure 7B. The row in Figure 7B represents all the signal 323 peaks from a specific sample, and the column represents the signal intensity of a 324 specific VOC in different wheat samples. In addition, the numbers in the Figure   325 represent the uncertainty of the identified substances in the migration spectrum 326 library. The specific VOCs related to aphid resistance were plotted against the 327 treatment of nano-Se, MT, and their combination as well as the control ( Figure 7C).

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The infestation of aphids in plants can cause huge damage to crop production.  (Table 1). This could be due 337 to the mechanism that nano-Se could promote the synthesis of flavones, phenolic  interact to regular and enhance plant resistance to insects [44]. It has been 398 demonstrated that the ROS and hormonal signaling were integrated to respond to 399 insect herbivores [45]. Silicon could also regulate the biosynthesis of phytohormones 400 (JA, SA and IAA) and reduce the concentration of ROS; these two processes together 401 enhance plant resistance to herbivorous insects [46]. In our study, nano-Se could found to regulate flavonoids and carotenoid biosynthesis as well [49], promote the 411 synthesis of amino acids, organic acids and sugars, and enhance the plant resilience 412 under biotic (fungi, bacteria, and insects) and abiotic (heat, cold, drought, and salt) 413 stresses [50]. DIMBOA is an allelochemical and can react with glucose to enhance 414 resistance to aphids by promoting the callose deposition in maize [51].   (Table S1) (Table S2); HPLC-MS/MS parameters of phenolic acids (Table S3)