Extrachromosomal DNA in the Apicomplexa

Wilson, Iain; Gardner, Malcolm J.; Rangachari, K.; Williamson, D. H.

doi:10.1007/978-3-642-78559-7_6

Cited by 45 publications

(57 citation statements)

References 61 publications

(56 reference statements)

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“…As representatives of nonphotosynthetic plastid-containing species, we initially included the parasitic seed plants Cuscuta reflexa (Funk et al, 2007) and Epifagus virginiana (Wolfe et al, 1992), the colorless heterotrophic alga Euglena longa (Astasia longa) (Gockel et al, 1994), and the apicomplexan parasites Eimeria tenella (Cai et al, 2003), Theileria parva (Gardner et al, 2005), and Toxoplasma gondii (Wilson and Williamson, 1997;Wilson, 2002). Recently, the plastome of the parasitic orchid Rhizanthella gardneri was fully sequenced (Delannoy et al, 2011).…”

Section: Targeted Disruption Of Seven Plastid Ribosomal Protein Genesmentioning

confidence: 99%

Nonessential Plastid-Encoded Ribosomal Proteins in Tobacco: A Developmental Role for Plastid Translation and Implications for Reductive Genome Evolution

et al. 2011

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Plastid genomes of higher plants contain a conserved set of ribosomal protein genes. Although plastid translational activity is essential for cell survival in tobacco (Nicotiana tabacum), individual plastid ribosomal proteins can be nonessential. Candidates for nonessential plastid ribosomal proteins are ribosomal proteins identified as nonessential in bacteria and those whose genes were lost from the highly reduced plastid genomes of nonphotosynthetic plastid-bearing lineages (parasitic plants, apicomplexan protozoa). Here we report the reverse genetic analysis of seven plastid-encoded ribosomal proteins that meet these criteria. We have introduced knockout alleles for the corresponding genes into the tobacco plastid genome. Five of the targeted genes (ribosomal protein of the large subunit22 [rpl22], rpl23, rpl32, ribosomal protein of the small subunit3 [rps3], and rps16) were shown to be essential even under heterotrophic conditions, despite their loss in at least some parasitic plastid-bearing lineages. This suggests that nonphotosynthetic plastids show elevated rates of gene transfer to the nuclear genome. Knockout of two ribosomal protein genes, rps15 and rpl36, yielded homoplasmic transplastomic mutants, thus indicating nonessentiality. Whereas Drps15 plants showed only a mild phenotype, Drpl36 plants were severely impaired in photosynthesis and growth and, moreover, displayed greatly altered leaf morphology. This finding provides strong genetic evidence that chloroplast translational activity influences leaf development, presumably via a retrograde signaling pathway.

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Section: Targeted Disruption Of Seven Plastid Ribosomal Protein Genesmentioning

confidence: 99%

Nonessential Plastid-Encoded Ribosomal Proteins in Tobacco: A Developmental Role for Plastid Translation and Implications for Reductive Genome Evolution

et al. 2011

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“…rpl20 (for ribosomal protein of the large subunit number 20), the gene encoding the ribosomal protein L20 (Rpl20) is absent from the plastid genomes of the parasitic protozoans Eimeria tenella (full genome accession number NC_004823), Theileria parva (full genome accession number NC_007758), and Toxoplasma gondii (full genome accession number NC_001799; Wilson et al, 1996;Wilson and Williamson, 1997;Wilson, 2002). Likewise, rpl33, the gene for protein L33 (Rpl33) is absent from the T. gondii plastid genome and from that of the colorless heterotrophic alga Euglena longa (also known as Astasia longa; Gockel et al, 1994; full genome accession number NC_002652).…”

Section: Introductionmentioning

confidence: 99%

Rpl33, a Nonessential Plastid-Encoded Ribosomal Protein in Tobacco, Is Required under Cold Stress Conditions

et al. 2008

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Plastid genomes contain a conserved set of genes encoding components of the translational apparatus. While knockout of plastid translation is lethal in tobacco (Nicotiana tabacum), it is not known whether each individual component of the plastid ribosome is essential. Here, we used reverse genetics to test whether several plastid genome-encoded ribosomal proteins are essential. We found that, while ribosomal proteins Rps2, Rps4, and Rpl20 are essential for cell survival, knockout of the gene encoding ribosomal protein Rpl33 did not affect plant viability and growth under standard conditions. However, when plants were exposed to low temperature stress, recovery of Rpl33 knockout plants was severely compromised, indicating that Rpl33 is required for sustaining sufficient plastid translation capacity in the cold. These findings uncover an important role for plastid translation in plant tolerance to chilling stress.

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“…Each process can be argued on the basis of biological precedents that involve splicing systems and that are not associated with obvious adaptive benefits. Steps such as these also occur in other contexts: apparently gratuitous fragmentation of genes whose products, nevertheless, associate after expression is seen for ribosomal RNA genes (Nedelcu 1997;Wilson and Williamson 1997); reduction or loss of an activity encoded in an element when this activity can be supplied by another copy of the element is seen in nonautonomous transposons (Iida et al 1983); and the accretion of multiple proteins to catalytic RNAs that are presumed to have operated ancestrally without proteins is suspected for ribosomes and ribonuclease P (Inoue 1994).…”

Section: Loss Of Self-splicing In Most Intronsmentioning

confidence: 99%

On the Possibility of Constructive Neutral Evolution

1999

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Abstract. The neutral theory often is presented as a theory of "noise" or silent changes at an isolated "molecular level," relevant to marking the steady pace of divergence, but not to the origin of biological structure, function, or complexity. Nevertheless, precisely these issues can be addressed in neutral models, such as those elaborated here with regard to scrambled ciliate genes, gRNA-mediated RNA editing, the transition from selfsplicing to spliceosomal splicing, and the retention of duplicate genes. All of these are instances of a more general scheme of "constructive neutral evolution" that invokes biased variation, epistatic interactions, and excess capacities to account for a complex series of steps giving rise to novel structures or operations. The directional and constructive outcomes of these models are due not to neutral allele fixations per se, but to these other factors. Neutral models of this type may help to clarify the poorly understood role of nonselective factors in evolutionary innovation and directionality.

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Extrachromosomal DNA in the Apicomplexa

Cited by 45 publications

References 61 publications

Nonessential Plastid-Encoded Ribosomal Proteins in Tobacco: A Developmental Role for Plastid Translation and Implications for Reductive Genome Evolution

Nonessential Plastid-Encoded Ribosomal Proteins in Tobacco: A Developmental Role for Plastid Translation and Implications for Reductive Genome Evolution

Rpl33, a Nonessential Plastid-Encoded Ribosomal Protein in Tobacco, Is Required under Cold Stress Conditions

On the Possibility of Constructive Neutral Evolution

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