In a recent publication, Zhang et al. investigate the promoters of four genes for their potential hemocyte-specific activity in Bombyx mori. Their investigations have resulted tools and resources for those in the silk worm community that are interested in hemocyte biology.
Hemocytes play a vital role in an insect’s development and immunity but the ability for scientists to manipulate this tissue type only exists in a few species. Hemocytes have been well characterized in Drosophila; however, in other insect species the tools for studying hemocytes are minimal. This lack of genetic and molecular tools, such as hemocyte-specific enhancers or promoters, makes hematopoesis, hemocyte development and function difficult to study.
In this study the investigators identified candidate hemocyte-specific genes through micro array analyses involving various silk worm tissue-types specifically looking for genes that had exceptional expression in the hemolymph of the insect. Once the candidates were identified they were confirmed by qPCR. Four genes, Bmintβ2, Bmintβ3, BmCatO, and BmSw04862 were identified that met the criteria for being hemocyte-specific.
Identifying the regulatory regions of genes first required the investigators to obtain the full length gene sequences. Subsequently, the upstream promoter regions were cloned into a viral expression vector, AcNPV, regulating the expression of DsRed.
Remarkably, the investigators were able to demonstrate hemocyte-specific DsRed activity from their viral transfection experiments through RT-PCR, flow cytometry and florescence microscopy. Knowing their promoters worked, they then truncated the promoter regions used to identify the minimal promoter for activity. Of the four gene promoters originally tested three had displayed hemocyte-specific activity.
The hemocyte-specific promoters that have been characterized in this publication are a first step in unlocking the capability of manipulation of hemocytes in the silk worm.
Zhang, K., Yu, S., Su, J., Xu, M., Tan, P. et al., 2015 Identification and characterization of three novel hemocyte-specific promoters in silkworm Bombyx mori. Biochem Biophys Res Commun 461: 102-108doi: http://dx.doi.org/10.1016/j.bbrc.2015.03.176.