Independent regulation of Plasmodium falciparum rif gene promoters

Rosana Beatriz Duque Araujo,Tatiane Macedo Silva,Diego Alonso,Gabriela Fernandes Leite,Paulo Eduardo Martins Ribolla,Gerhard Wunderlich,Charlotte Sophie Kaiser

doi:10.1038/s41598-018-27646-0

Rosana Beatriz Duque Araujo, Tatiane Macedo Silva + Show 5 more

Open Access

https://doi.org/10.1038/s41598-018-27646-0

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Abstract

All Plasmodium species express variant antigens which may mediate immune escape in the vertebrate host. In Plasmodium falciparum, the rif gene family encodes variant antigens which are partly exposed on the infected red blood cell surface and may function as virulence factors. Not all rif genes are expressed at the same time and it is unclear what controls rif gene expression. In this work, we addressed global rif transcription using plasmid vectors with two drug resistance markers, one controlled by a rif 5′ upstream region and the second by a constitutively active promoter. After spontaneous integration into the genome of one construct, we observed that the resistance marker controlled by the rif 5′ upstream region was expressed dependent on the applied drug pressure. Then, the global transcription of rif genes in these transfectants was compared in the presence or absence of drugs. The relative transcript quantities of all rif loci did not change profoundly between strains grown with or without drug. We conclude that either there is no crosstalk between rif loci or that the elusive system of allelic exclusion of rif gene transcription is not controlled by their 5′ upstream region alone.

Highlights

The infection with one of the five Plasmodium species which cause malaria in humans still is a challenge for the public health predominantly in underdeveloped countries
In order to test if rif genes are expressed in a coordinated way as var genes[33], we created bicistronic plasmids similar to those used by Voss[7] or Witmer[31] and colleagues
Reinforces that “A”-grouped rif 5′ ups, encoding antigens which are potentially associated with the infected red blood cell surface, are not influenced by an artificially activated “A” type rif 5′-ups

Summary

Introduction

The infection with one of the five Plasmodium species which cause malaria in humans still is a challenge for the public health predominantly in underdeveloped countries. Still more elusive is what determines that a var locus and its associated histone modifications switch from an active to a silent state or vice versa Another major variant gene family which is found in human or primate Plasmodium species and in murine species is the pir (Plasmodium interspersed repeat) gene family[15], and the biological function of gene products from this family is not well understood. PCR results showing amplification with forward hDHFR and forward bsd primers (in red) over the backbone of the transfection plasmid (positive for the untransfected plasmid (2) as well as the gDNA from the PF3D7_0200700 5′ rif ups transfected strain).

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