Grosvenorine

23889909

Background
Several eukaryotic parasites form cysts that transmit infection. The process is found in diverse organisms such as Toxoplasma, Giardia, and nematodes. In Entamoeba histolytica this process cannot be induced in vitro, making it difficult to study. In Entamoeba invadens, stage conversion can be induced, but its utility as a model system to study developmental biology has been limited by a lack of genomic resources. We carried out genome and transcriptome sequencing of E. invadens to identify molecular processes involved in stage conversion.

Results
We report the sequencing and assembly of the E. invadens genome and use whole transcriptome sequencing to characterize changes in gene expression during encystation and excystation. The E. invadens genome is larger than that of E. histolytica, apparently largely due to expansion of intergenic regions; overall gene number and the machinery for gene regulation are conserved between the species. Over half the genes are regulated during the switch between morphological forms and a key signaling molecule, phospholipase D, appears to regulate encystation. We provide evidence for the occurrence of meiosis during encystation, suggesting that stage conversion may play a key role in recombination between strains.

Conclusions
Our analysis demonstrates that a number of core processes are common to encystation between distantly related parasites, including meiosis, lipid signaling and RNA modification. These data provide a foundation for understanding the developmental cascade in the important human pathogen E. histolytica and highlight conserved processes more widely relevant in enteric pathogens.

The genome and transcriptome of the enteric parasite Entamoeba invadens, a model for encystation

Gretchen M Ehrenkaufer,#1 Gareth D Weedall,#2 Daryl Williams,2 Hernan A Lorenzi,3 Elisabet Caler,3 Neil Hall,corresponding author#2,4 and Upinder Singhcorresponding author#1,5

2013;

30078931

Restrictions on staple or cash crop exports are frequently imposed in developing countries to promote food security or industrial development. By diverting production to local markets, these policies tend to reduce prices and increase domestic supply of food or intermediate inputs in the short term, to the benefit of consumers or manufacturers, which make them attractive to policymakers. However, in the long term, export restrictions discourage agricultural production, which may ultimately negate the short-term gains. This study assesses the economy-wide effects of Malawi’s long-term maize export ban, which was only recently lifted, and a proposed oilseed export levy intended to improve food security and support local processing industries, respectively. We find that maize export bans only benefit the urban non-poor, while poor farmers’ incomes and maize consumption levels decline in the longer run. The oilseed export levy also fails to achieve its long run objectives: even when tax revenues are used to further subsidize food processors, their gains in value-addition are outweighed by declining agricultural value-addition. More generally, these results show that while export restrictions may have the desired outcomes in the short run, production responses may render the policies ineffective in the medium to long run. Ultimately, such restrictive policies reinforce a subsistence approach to agriculture, which is inconsistent with the stated economic transformation goals of many Sub-Saharan African countries.

Malawi, Export restrictions, Trade policy, CGE modelling

Achieving food security and industrial development in Malawi: Are export restrictions the solution?

Emerta Aragie,a Karl Pauw,b,⁎ and Valentina Pernechelea

2018 Aug;