Two storage hexamerins from the beet armyworm Spodoptera exigua: Cloning, characterization and the effect of gene silencing on survival

Abstract

BackgroundIn insects, hemocyanin superfamily proteins accumulate apparently to serve as sources of amino acids during metamorphosis, reproduction and development. Storage hexamerins are important members of the hemocyanin superfamily. Although insects possess storage hexamerins, very little is known about the character and specific functions of hexamerin 1 and storage protein 1 in insect development.ResultsTo gain insight into the function of storage proteins in insects, cDNAs for two storage proteins were cloned from the fat body of Spodoptera exigua. S. exigua hexamerin 1 (SeHex) cDNA contained an open reading frame of 2124 nucleotides encoding a protein of 707 amino acids with a predicted molecular weight of 82.12 kDa. S. exigua storage protein 1 (SeSP1) cDNA contained an open reading frame of 2256 bp encoding a protein of 751 amino acids with a predicted molecular weight of ~88.84 kDa. Northern blotting analyses revealed that SeHex mRNA is expressed in the fat body, cuticle, midgut and Malpighian tubules and SeSP1 in fat body, Malpighian tubules and tracheae. SeHex and SeSP1 mRNAs were expressed in fat body at different levels from first instar larvae to pupae, with expression was much lower from first instar larvae to first-day fifth instar larvae. SeHex transcript expression was high in fat body of wandering larvae (pre-pupae) and steadily decreased to the seventh pupal day. SeSP1 transcript expression was high in fat body of wandering larvae, 2-day-old fifth instar larvae and 2-, 4- and 7-day-old pupae. SeHex and SeSP1 mRNAs levels were expressed lower than control on the condition of starvation at 12 h. Of insects injected with SeHex and SeSP1 dsRNA, 38.7% and 24.3% survived to 204 h after treatment, respectively. This was significantly lower than in the controls groups.ConclusionsThese findings provide new data on the tissue distribution, expression patterns and the function in starvation of storage proteins. RNA interference results revealed that storage protein genes are key in metamorphosis, reproduction and insect development. The results for SeHex and SeSP1 interference reveal that a potential method to control this pest is to disrupt the regulation of storage proteins.

A novel hexamerin with an unexpected contribution to the prophenoloxidase activation system of the Chinese oak silkworm, Antheraea pernyi

“…Further investigations on the tissue distribution revealed that Ap-hexamerin was also expressed at a non-negligible level in the epidermis and Malpighian tubule but rarely detected in the midgut and haemocytes under physiological conditions (Figure 2b-d). This result coincides with that of hexamerin in the beet armyworm, Spodoptera exigua, in which hexamerin was detected in the fat body, Malpighian tubule, cuticle, and midgut (Tang et al, 2010). Recently, two studies on honeybees showed the intranuclear localization of hexamerins in sexual organs, probably functioning as nucleolus proteins in developing and mature (Martins & Bitondi, 2016;Martins, Anhezini, Dallacqua, Simoes, & Bitondi, 2011).…”

“…Most of the storage proteins are identified as hexamerins, a group of respiratory hemocyaninderived proteins that lost the ability to transport oxygen (Burmester, 2002;Telfer & Kunkel, 1991). A number of hexamerins have been identified in arthropods (Burmester, 2015;Cristino et al, 2010;Cunha, Nascimento, Guidugli, Simoes, & Bitondi, 2005;Liang, Xie, & Luan, 2019;Martins & Bitondi, 2012;Pick, Hagner-Holler, & Burmester, 2008;Tsai, Chen, & Tsai, 2014), but research in recent decades has demonstrated that in addition to providing energy as storage proteins in the nonfeeding stage, hexamerins also take part in many other physiological processes, including egg production (Wheeler, Tuchinskaya, Buck, & Tabashnik, 2000), hormone transport (Ashfaq, Sonoda, & Tsumuki, 2007;Rao, Ningshen, Chaitanya, Senthilkumaran, & Dutta-Gupta, 2016), caste regulation (Hawkings, Calkins, Pietrantonio, & Tamborindeguy, 2019;Zhou, Tarver, Bennett, Oi, & Scharf, 2006), diapause (Spiliotopoulos, Gkouvitsas, Fantinou, & Kourti, 2007), and even immune responses (Fallon, Troy, & Kavanagh, 2011;Poopathi et al, 2014;Tang, Wang, & Zhang, 2010).…”

Transcriptional Analysis of The Adaptive Digestive System of The Migratory Locust in Response to Plant Defensive Protease Inhibitors

“…5). In contrast, knockdown of two important storage proteins, SeHex and SeSp1 in Spodoptera exigua resulted in increased mortality, suggested to be caused by a lack of nutritional reserves46. However, in this study, we only targeted the group of hexamerins that were upregulated in the gut after PI ingestion.…”

Silencing Abnormal Wing Disc Gene of the Asian Citrus Psyllid, Diaphorina citri Disrupts Adult Wing Development and Increases Nymph Mortality

“…RNAi experiments have been conducted on insects that belong to different taxonomic groups, particularly Holometabolous insects: Lepidopterans; Bombyx mori , Manduca sexta , Helicoverpa armigera [41], Spodoptera Exigua [23], [42] Plutella xylostella [26], dipterans; D. melanogaster , Bactrocera Dorsalis [43], and coleopterans; Diabrotica virgifera [44], [45]. Fewer studies have been carried out on Hemimetabolous insects: Isoptera; termite Reticulitermes flavipes [46], Orthoptera; Locusta migratoria [47] Gryllus bimaculatus [40]; Hemiptera and Homoptera; Rhodnius prolixus [48], Nilaparvata lugens [49], [50], Laodelphax striatellus [50], Bemisia tabaci [51] Bacterocera cockerelli [52] and Acyrthosiphon pisum [53].…”