Evolution of chloroplast transcript processing in Plasmodium and its chromerid algal relatives

Area of Science:

• * Molecular biology
• * Evolutionary biology
• * Parasitology

Background:

• * Apicomplexan parasites, like Plasmodium, evolved from algae and possess non-photosynthetic chloroplasts.
• * Recently discovered chromerid algae (Chromera velia, Vitrella brassicaformis) retain functional chloroplasts and photosynthesis.
• * Studying chromerids offers insights into apicomplexan origins and the loss of photosynthesis.

Purpose of the Study:

• * Characterize chloroplast transcript processing in chromerids and Plasmodium.
• * Investigate the role of 3' poly(U) tail addition in gene expression.
• * Explore the evolutionary implications for photosynthesis loss in apicomplexans.

Main Methods:

• * Comparative analysis of chloroplast transcript processing pathways.
• * Focus on 3' poly(U) tail addition in C. velia, V. brassicaformis, and P. falciparum.
• * Gene expression analysis and transcript abundance studies.

Main Results:

• * Chromerid chloroplasts preferentially add poly(U) tails to transcripts encoding photosynthetic electron transfer proteins.
• * This represents a novel, functionally-categorized chloroplast transcript processing pathway.
• * Plasmodium chloroplast transcripts lack polyuridylylation; chromerid poly(U) tails are linked to polycistronic precursor processing and high transcript abundance.

Conclusions:

• * Poly(U) tail addition in chromerids is a unique regulatory mechanism associated with photosynthesis gene expression.
• * The absence of this pathway in Plasmodium correlates with the loss of photosynthesis.
• * Alterations in chloroplast transcript processing machinery likely played a key role in the evolutionary transition from photosynthetic algae to parasitic apicomplexans.