The English grain aphid (Sitobion avenae F.) is one of the most important and destructive pests in wheat production worldwide. Lipoxygenase (LOX) is a key rate-limiting enzyme in the bio-synthesis pathway of jasmonate and methyl jasmonate in plants and animals. This enzyme is essential for plant growth and for biotic and abiotic stresses response. In this study, the TtLOX gene from wheat (Triticum turgidum) was isolated and characterized, and its conserved domains, phylogenetic relationship and subcellular localization were investigated. As a 2787-bp open reading frame (ORF) gene, TtLOX was predicted to encode a protein of 928-amino acid. TtLOX transcription was up-regulated in response to aphid feeding; the expression of TtLOX in wheat leaves was significantly higher in Lanmai, an aphid-resistant variety, than in Poland 305, an aphid-sensitive variety. In contrast, TtLOX expression was down-regulated both in individuals treated with methyl-jasmine (MeJA) and in individuals with the TtLOX gene silenced by barley stripe mosaic virus (BSMV). The aphid numbers on the MeJA treated plants and on the TtLOX gene-silenced plants were higher than that on the control plants. These results suggest that the TtLOX gene may have potential as a target gene for controlling Sitobion avenae in wheat.
Clip cages are commonly used to confine aphids or other small insects to a single leaf when conducting plant–small insect interaction studies; however, clip cages are usually heavy or do not efficiently transmit light, which has an impact on leaf physiology, limiting their application. Here, simple, lightweight, and transparent modified clip cages were constructed using punched clear plastic cups, cut transparent polyvinyl chloride sheets, nylon organdy mesh, and bent duck-bill clips. These cages can be clipped directly onto dicot leaves or attached to monocot leaves with bamboo skewers and elastic bands. The weight, production time, and aphid escape rates of the modified clip cages were 3.895 ± 0.004 g, less than 3 min, and 2.154 ± 0.323%, respectively. The effects of the modified clip cage on the growth, development, and reproduction of the English grain aphid (Sitobion avenae Fabricius) in comparison with the whole cage were studied. The biochemical responses of wheat (Triticum aestivum) to the cages were also investigated. No significant differences were observed in the life table parameters, nymph mortality, and adult fecundity in S. avenae confined to clip cages and whole cages, but the clip cages were more time efficient than whole cages when conducting life table studies. Moreover, the hydrogen peroxide accumulation, callose deposition, and cell necrosis in wheat leaves covered by empty clip cages and empty whole cages were similar, and significantly lower than treatments where the aphids were inside the clip cage. The results demonstrate that the modified clip cages had negligible effects on the plant and aphid physiology, suggesting that they are effective for studying plant–small insect interactions.
The grain aphid Sitobion avenae (Fabricius) is one of the most destructive pests of wheat (Triticum aestivum). Deployment of resistant wheat germplasm appears as an excellent solution for this problem. Elite bread wheat cultivars only have limited resistance to this pest. The present study was carried out to investigate the potential of the tetraploid wheat (Triticum turgidum) variety Lanmai, which showed high resistance to S. avenae at both seedling and adult plant stages, as a source of resistance genes. Based on apterous adult aphids’ fecundity tests and choice bioassays, Lanmai has been shown to display antixenosis and antibiosis. Suppression subtractive hybridization (SSH) was employed to identify and isolate the putative candidate defense genes in Lanmai against S. avenae infestation. A total of 134 expressed sequence tags (ESTs) were identified and categorized based on their putative functions. RT-qPCR analysis of 30 selected genes confirmed their differential expression over time between the resistant wheat variety Lanmai and susceptible wheat variety Polan305 during S. avenae infestation. There were 11 genes related to the photosynthesis process, and only 3 genes showed higher expression in Lanmai than in Polan305 after S. avenae infestation. Gene expression analysis also revealed that Lanmai played a critical role in salicylic acid and jasmonic acid pathways after S. avenae infestation. This study provided further insights into the role of defense signaling networks in wheat resistance to S. avenae and indicates that the resistant tetraploid wheat variety Lanmai may provide a valuable resource for aphid tolerance improvement in wheat.
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