Submitted to: Insect Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2015
Publication Date: 5/28/2015
Publication URL: http://handle.nal.usda.gov/10113/60962
Citation: Shelby, K., Perera, O.P., Snodgrass, G.L. 2015. Expression profiles of Astakine-like transcripts in the tarnished plant bug, Lygus lineolaris, exposed to fungal spores of Beauveria bassiana. Insect Molecular Biology. 24(4):480-490. DOI:10.1111/imb.12175.
Interpretive Summary: Astakines are small proteins that were originally characterized in crustaceans as signaling molecules involved in regulating circadian rhythm and hematopoiesis. Astakines are analogous to cytokines, a broad category of cell signaling molecules found in vertebrates. Three astakine-like proteins (LlAst-1, LlAst-2, and LlAst-3) were identified in the tarnished plant bug, an important pest of cotton in the southern United States. In this study, messenger RNA sequences of the three astakine-like proteins were characterized and expression patterns of these three proteins in different tissues, at different times of the day, and during the course of infection of the plant bugs by a pathogenic fungus was studied. Highest levels of the LlAst1 and LlAst-2 were observed in the fat body while Ast3 was highest in the legs. The expression levels fluctuated between day and night. LLAst-1 levels in plant bugs infected with the pathogenic fungus increased significantly in 24-48 hours post inoculation, while the levels of LlAst-2 and LlAst-3 decreased with the progression of the fungal infection. Compared to mid-day, high expression levels of LlAst-1 were observed at 6 pm and midnight samples of both males and females and remained high at 6 am in males. LlAst-3 had different expression patterns in males and females. Role these astakine-like sequences play in immunity to pathogens is discussed.
Technical Abstract: Astakines are hematopoietic cytokines originally isolated from crustaceans. We identified three astakine-like transcripts in the tarnished plant bug, LlAst-1, LlAst-2, and LlAst-3, containing prokineticin domains. Quantitative real-time PCR demonstrated variation in expression patterns of astakines in different tissues and between sexes. Relative expression levels of LlAst-1was highest in the fat bodies of females, while LlAst-2 expression was highest in the fat bodies of both males and females. LlAst-3 expression was higher in male legs compared to the female legs, but lower in all other tissues. Infection with the entomopathogenic fungus Beauveria bassiana slightly elevated LlAst-1 expression 48 hrs post infection in both males and females. In contrast, the expression of LlAst-2 and LlAst-3 were not significantly changed in males and females. Compared to 12 noon, LlAst-1 level was higher in both sexes at 6 pm and midnight. By 6 am LlAst-1 level in females was significantly reduced while that in males remained high. LlAst-2 and -3 had highest relative expression levels in females at midnight but were significantly lower than in males at midnight and in both sexes at 6 pm and 6 am. This is the first report of expression of astakine-like cytokines from insects.