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Title: A PROTEIN WITH GROWTH FACTOR-LIKE ACTIVITY AND HOMOLOGY TO ALPHA-1-ACID GLYCOPROTEIN HAS BEEN IDENTIFIED IN TESTIS SHEATHS OF THE LEPIDOPTERAN, HELIOTHIS VIRESCENS

Author
item LOEB, MARCIA
item JAFFE, HOWARD - NATIONAL INST. OF HEALTH

Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/27/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: The Lepidopteran, Heliothis virescens, is very resistant to commonly used insecticides and often becomes established in cotton fields after more susceptible pests, such as the boll weevil, have succumbed to standard treatments. It has several generations a year, and migrates further north with each generation. Therefore one important aspect of study is to understand how the differentiation of its reproductive system is controlled in order to devise effective biocontrol measures. Regulatory factors are also of use in tissue culture systems where management of insect cell growth and development are being studied. We have identified a protein produced by the testes of H. virescens that induces cell division and differentiation of the male genital tract in tissue culture. It is identified as a form of alpha-1-acid glycoprotein, recognized as a blood protein in many animals. This protein is conserved in evolution, and may serve both insects and fetal vertebrates as a growth factor. This information will be used by other scientists to better design Lepidopteran control programs, and in tissue culture laboratories where differentiation is being studied

Technical Abstract: Early pupae of Heliothis virescens possess immature genital tracts with poorly developed epithelia and minute lumens. As 20-hydroxyecdysone (20HE) titers rise in the hemolymph, epithelial cells undergo mitosis and develop into large muscular organs with wide lumens, capable of propelling sperm from the testes down the tract. This occurs in vitro when genital tracts are cultured in medium containing 20- hydroxyecdysone and testis sheaths (Loeb 1991). In this work, immature testis sheaths were induced to synthesize the material that caused tract development; an aqueous extract of the testis sheaths was separated using polyacrylamide gel chromatography and RP-HPLC. The active material, a 53 KDa protein initiated lumen widening and tritiated thymidine incorporation. It was identified as bovine alpha-1-acid glycoprotein after digestion with endoproteinase Lys-C and sequencing of a fragment, (K)NVGVSFYADKPEVTQEQ.., that showed considerable homology to a similar portion of porcine and bovine alpha-1-acid glycoprotein. Extract prepared from testes incubated without bovine fetal calf serum also had duct widening activity. Commercially available bovine alpha-1-acid glycoprotein induced duct widening and thymidine incorporation as well. The data suggests that an alpha-1-acid glycoprotein produced by insect testis sheaths acts as a growth factor in insect genital tract development.