Expression of vesicular transport genes in avisicular cells of microsporidia Paranosema (Antonospora) locustae

Abstract

The long-term adaptation of microsporidia, a large group of fungi-related protozoa, to the intracellular lifestyle has resulted in a drastic minimization of the parasite cell. An ultrastructural analysis shows that the Golgi complex of microsporidia Paranosema (Antonospora) grylli and P. locustae appears as branching networks of thin tubules. These tubular networks are connected with the endoplasmic reticulum, plasma membrane, and forming polar tube, but have no vesicles. Vesicles were not found, even with the use of ultrafast cryofixation and membrane fusion/uncoating inhibition techniques. However, it was found that microsporidia genome has a number of genes involved in vesicular transport. In this study we used RT-PCR to analyze the content of mRNA transcripts encoding β and β′-subunits of COPI coatomer complex, Sec13 and Sec31 subunits of COPI, SNARE-protein synaptobrevin and syntaxin-like member of SFT family in P. locustae at intracellular stages of development. The expression level of these genes was comparable to that of the gene that encodes alternative oxidase, an enzyme engaged in the core metabolism of microsporidia. Moreover, the application of polyclonal antibodies raised against the recombinant COPII subunit Sec13 expressed in E. coli revealed the association of protein with membranes and its accumulation in spores and at stages of intracellular development. The presence of components of vesicular transport machinery in avesicular microsporidia cells requires their functional analysis.