CaaX-Like Protease of Cyanobacterial Origin Is Required for Complex Plastid Biogenesis in Malaria Parasites

ABSTRACT Plasmodium parasites and related apicomplexans contain an essential “complex plastid” organelle of secondary endosymbiotic origin, the apicoplast. Biogenesis of this complex plastid poses a unique challenge requiring evolution of new cellular machinery. We previously conducted a mutagenesis...

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Autores principales:	Thomas R. Meister, Yong Tang, Michael J. Pulkoski-Gross, Ellen Yeh
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2020
Materias:	Plasmodium apicoplast apicoplast biogenesis CaaX protease postprenylation processing AMR4 Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/8f599106eaa848e9b991e452c8a1cad0
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spelling	oai:doaj.org-article:8f599106eaa848e9b991e452c8a1cad02021-11-15T16:19:08ZCaaX-Like Protease of Cyanobacterial Origin Is Required for Complex Plastid Biogenesis in Malaria Parasites10.1128/mBio.01492-202150-7511https://doaj.org/article/8f599106eaa848e9b991e452c8a1cad02020-10-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01492-20https://doaj.org/toc/2150-7511ABSTRACT Plasmodium parasites and related apicomplexans contain an essential “complex plastid” organelle of secondary endosymbiotic origin, the apicoplast. Biogenesis of this complex plastid poses a unique challenge requiring evolution of new cellular machinery. We previously conducted a mutagenesis screen for essential apicoplast biogenesis genes to discover organellar pathways with evolutionary and biomedical significance. Here we validate and characterize a gene candidate from our screen, Pf3D7_0913500. Using a conditional knockdown strain, we show that Pf3D7_0913500 depletion causes growth inhibition that is rescued by the sole essential product of the apicoplast, isopentenyl pyrophosphate (IPP), and results in apicoplast loss. Because Pf3D7_0913500 had no previous functional annotation, we name it apicoplast-minus IPP-rescued 4 (AMR4). AMR4 has an annotated CaaX protease and bacteriocin processing (CPBP) domain, which in eukaryotes typically indicates a role in CaaX postprenylation processing. Indeed, AMR4 is the only putative CaaX-like protease in Plasmodium parasites which are known to require protein prenylation, and we confirm that the conserved catalytic residue of AMR4 (E352) is required for its apicoplast function. However, we unexpectedly find that AMR4 does not act in a CaaX postprenylation processing pathway in Plasmodium falciparum. Instead, we find that AMR4 is imported into the apicoplast and is derived from a cyanobacterial CPBP gene which was retained through both primary and secondary endosymbiosis. Our findings suggest that AMR4 is not a true CaaX protease, but instead it performs a conserved, uncharacterized chloroplast function that has been retained for complex plastid biogenesis. IMPORTANCE Plasmodium parasites, which cause malaria, and related apicomplexans are important human and veterinary pathogens. These parasites represent a highly divergent and understudied branch of eukaryotes, and as such often defy the expectations set by model organisms. One striking example of unique apicomplexan biology is the apicoplast, an essential but nonphotosynthetic plastid derived from an unusual secondary (eukaryote-eukaryote) endosymbiosis. Endosymbioses are a major driver of cellular innovation, and apicoplast biogenesis pathways represent a hot spot for molecular evolution. We previously conducted an unbiased screen for apicoplast biogenesis genes in P. falciparum to uncover these essential and innovative pathways. Here, we validate a novel gene candidate from our screen and show that its role in apicoplast biogenesis does not match its functional annotation predicted by model eukaryotes. Our findings suggest that an uncharacterized chloroplast maintenance pathway has been reused for complex plastid biogenesis in this divergent branch of pathogens.Thomas R. MeisterYong TangMichael J. Pulkoski-GrossEllen YehAmerican Society for MicrobiologyarticlePlasmodiumapicoplastapicoplast biogenesisCaaX proteasepostprenylation processingAMR4MicrobiologyQR1-502ENmBio, Vol 11, Iss 5 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	Plasmodium apicoplast apicoplast biogenesis CaaX protease postprenylation processing AMR4 Microbiology QR1-502
spellingShingle	Plasmodium apicoplast apicoplast biogenesis CaaX protease postprenylation processing AMR4 Microbiology QR1-502 Thomas R. Meister Yong Tang Michael J. Pulkoski-Gross Ellen Yeh CaaX-Like Protease of Cyanobacterial Origin Is Required for Complex Plastid Biogenesis in Malaria Parasites
description	ABSTRACT Plasmodium parasites and related apicomplexans contain an essential “complex plastid” organelle of secondary endosymbiotic origin, the apicoplast. Biogenesis of this complex plastid poses a unique challenge requiring evolution of new cellular machinery. We previously conducted a mutagenesis screen for essential apicoplast biogenesis genes to discover organellar pathways with evolutionary and biomedical significance. Here we validate and characterize a gene candidate from our screen, Pf3D7_0913500. Using a conditional knockdown strain, we show that Pf3D7_0913500 depletion causes growth inhibition that is rescued by the sole essential product of the apicoplast, isopentenyl pyrophosphate (IPP), and results in apicoplast loss. Because Pf3D7_0913500 had no previous functional annotation, we name it apicoplast-minus IPP-rescued 4 (AMR4). AMR4 has an annotated CaaX protease and bacteriocin processing (CPBP) domain, which in eukaryotes typically indicates a role in CaaX postprenylation processing. Indeed, AMR4 is the only putative CaaX-like protease in Plasmodium parasites which are known to require protein prenylation, and we confirm that the conserved catalytic residue of AMR4 (E352) is required for its apicoplast function. However, we unexpectedly find that AMR4 does not act in a CaaX postprenylation processing pathway in Plasmodium falciparum. Instead, we find that AMR4 is imported into the apicoplast and is derived from a cyanobacterial CPBP gene which was retained through both primary and secondary endosymbiosis. Our findings suggest that AMR4 is not a true CaaX protease, but instead it performs a conserved, uncharacterized chloroplast function that has been retained for complex plastid biogenesis. IMPORTANCE Plasmodium parasites, which cause malaria, and related apicomplexans are important human and veterinary pathogens. These parasites represent a highly divergent and understudied branch of eukaryotes, and as such often defy the expectations set by model organisms. One striking example of unique apicomplexan biology is the apicoplast, an essential but nonphotosynthetic plastid derived from an unusual secondary (eukaryote-eukaryote) endosymbiosis. Endosymbioses are a major driver of cellular innovation, and apicoplast biogenesis pathways represent a hot spot for molecular evolution. We previously conducted an unbiased screen for apicoplast biogenesis genes in P. falciparum to uncover these essential and innovative pathways. Here, we validate a novel gene candidate from our screen and show that its role in apicoplast biogenesis does not match its functional annotation predicted by model eukaryotes. Our findings suggest that an uncharacterized chloroplast maintenance pathway has been reused for complex plastid biogenesis in this divergent branch of pathogens.
format	article
author	Thomas R. Meister Yong Tang Michael J. Pulkoski-Gross Ellen Yeh
author_facet	Thomas R. Meister Yong Tang Michael J. Pulkoski-Gross Ellen Yeh
author_sort	Thomas R. Meister
title	CaaX-Like Protease of Cyanobacterial Origin Is Required for Complex Plastid Biogenesis in Malaria Parasites
title_short	CaaX-Like Protease of Cyanobacterial Origin Is Required for Complex Plastid Biogenesis in Malaria Parasites
title_full	CaaX-Like Protease of Cyanobacterial Origin Is Required for Complex Plastid Biogenesis in Malaria Parasites
title_fullStr	CaaX-Like Protease of Cyanobacterial Origin Is Required for Complex Plastid Biogenesis in Malaria Parasites
title_full_unstemmed	CaaX-Like Protease of Cyanobacterial Origin Is Required for Complex Plastid Biogenesis in Malaria Parasites
title_sort	caax-like protease of cyanobacterial origin is required for complex plastid biogenesis in malaria parasites
publisher	American Society for Microbiology
publishDate	2020
url	https://doaj.org/article/8f599106eaa848e9b991e452c8a1cad0
work_keys_str_mv	AT thomasrmeister caaxlikeproteaseofcyanobacterialoriginisrequiredforcomplexplastidbiogenesisinmalariaparasites AT yongtang caaxlikeproteaseofcyanobacterialoriginisrequiredforcomplexplastidbiogenesisinmalariaparasites AT michaeljpulkoskigross caaxlikeproteaseofcyanobacterialoriginisrequiredforcomplexplastidbiogenesisinmalariaparasites AT ellenyeh caaxlikeproteaseofcyanobacterialoriginisrequiredforcomplexplastidbiogenesisinmalariaparasites
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CaaX-Like Protease of Cyanobacterial Origin Is Required for Complex Plastid Biogenesis in Malaria Parasites

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