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Rec-8 dimorphism affects longevity, stress resistance and X-chromosome nondisjunction in C. elegans, and replicative lifespan in S. cerevisiae.

Ayyadevara S, Tazearslan C, Alla R, Jiang JC, Jazwinski SM, Shmookler Reis RJ - Front Genet (2014)

Bottom Line: A single gene in this interval is now shown to modulate all lsq4-associated traits.Full-genome analysis of transcript levels indicates that lsq4 contains a dimorphic gene governing the expression of many sperm-specific genes, suggesting an effect on spermatogenesis.Fourteen "dual-candidate" genes, implicated by both position and expression, were tested for RNA-interference effects on QTL-linked traits.

View Article: PubMed Central - PubMed

Affiliation: Central Arkansas Veterans Healthcare System, VA Medical Center Little Rock, AR, USA ; Department of Geriatrics, University of Arkansas for Medical Sciences Little Rock, AR, USA.

ABSTRACT
A quantitative trait locus (QTL) in the nematode C. elegans, "lsq4," was recently implicated by mapping longevity genes. QTLs for lifespan and three stress-resistance traits coincided within a span of <300 kbp, later narrowed to <200 kbp. A single gene in this interval is now shown to modulate all lsq4-associated traits. Full-genome analysis of transcript levels indicates that lsq4 contains a dimorphic gene governing the expression of many sperm-specific genes, suggesting an effect on spermatogenesis. Quantitative analysis of allele-specific transcripts encoded within the lsq4 interval revealed significant, 2- to 15-fold expression differences for 10 of 33 genes. Fourteen "dual-candidate" genes, implicated by both position and expression, were tested for RNA-interference effects on QTL-linked traits. In a strain carrying the shorter-lived allele, knockdown of rec-8 (encoding a meiotic cohesin) reduced its transcripts 4-fold, to a level similar to the longer-lived strain, while extending lifespan 25-26%, whether begun before fertilization or at maturity. The short-lived lsq4 allele also conferred sensitivity to oxidative and thermal stresses, and lower male frequency (reflecting X-chromosome non-disjunction), traits reversed uniquely by rec-8 knockdown. A strain bearing the longer-lived lsq4 allele, differing from the short-lived strain at <0.3% of its genome, derived no lifespan or stress-survival benefit from rec-8 knockdown. We consider two possible explanations: high rec-8 expression may include increased "leaky" expression in mitotic cells, leading to deleterious destabilization of somatic genomes; or REC-8 may act entirely in germ-line meiotic cells to reduce aberrations such as non-disjunction, thereby blunting a stress-resistance response mediated by innate immunity. Replicative lifespan was extended 20% in haploid S. cerevisiae (BY4741) by deletion of REC8, orthologous to nematode rec-8, implying that REC8 disruption of mitotic-cell survival is widespread, exemplifying antagonistic pleiotropy (opposing effects on lifespan vs. reproduction), and/or balancing selection wherein genomic disruption increases genetic variation under harsh conditions.

No MeSH data available.


Related in: MedlinePlus

Rec-8 knockdown improves resistance to oxidative and thermal stresses, dependent on the lsq4–region background. Groups of 30 worms were fed on bacteria induced to express the indicated dsRNA (or empty expression vector) for 3 days from the L4/adult molt. They were then transferred to medium containing paraquat, and their subsequent survival monitored (see Methods). Of the indicated genes targeted by dsRNAs, only K09B11.5 had been found to be expressed at higher levels in CL2a, the longer-lived strain, and thus predicted to possibly reduce CL2a survival; the other 4 genes were expressed at higher levels in SR708, and thus were predicted to extend survival of treated SR708, if causal to the QTL effect on paraquat resistance. (A,B) Time courses of paraquat survival for control and dsRNA-treated adult worms, either (A) strain SR708, or (B) strain CL2a. (C,D). Paraquat dose-response curves for control vs. dsRNA-treated adults of strain (C) strain SR708, or (D) strain CL2a. (E,F) Thermotolerance survivals following abrupt transfer of standard survival plates from 20 to 35.5°C, containing control or dsRNA-treated adults of (E) strain SR708, or (F) strain CL2a. Each panel for heat-shock survival shows combined results from two independent experiments (solid and dashed lines indicate experiments 1 and 2, respectively). All panels show data representative of 2–4 experiments of each type.
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Figure 2: Rec-8 knockdown improves resistance to oxidative and thermal stresses, dependent on the lsq4–region background. Groups of 30 worms were fed on bacteria induced to express the indicated dsRNA (or empty expression vector) for 3 days from the L4/adult molt. They were then transferred to medium containing paraquat, and their subsequent survival monitored (see Methods). Of the indicated genes targeted by dsRNAs, only K09B11.5 had been found to be expressed at higher levels in CL2a, the longer-lived strain, and thus predicted to possibly reduce CL2a survival; the other 4 genes were expressed at higher levels in SR708, and thus were predicted to extend survival of treated SR708, if causal to the QTL effect on paraquat resistance. (A,B) Time courses of paraquat survival for control and dsRNA-treated adult worms, either (A) strain SR708, or (B) strain CL2a. (C,D). Paraquat dose-response curves for control vs. dsRNA-treated adults of strain (C) strain SR708, or (D) strain CL2a. (E,F) Thermotolerance survivals following abrupt transfer of standard survival plates from 20 to 35.5°C, containing control or dsRNA-treated adults of (E) strain SR708, or (F) strain CL2a. Each panel for heat-shock survival shows combined results from two independent experiments (solid and dashed lines indicate experiments 1 and 2, respectively). All panels show data representative of 2–4 experiments of each type.

Mentions: Paraquat exposure constitutes a toxic oxidative stress, through generation of superoxide radical (Ebert et al., 1993, 1996; Ayyadevara et al., 2001, 2003; Shmookler Reis et al., 2007). As illustrated in Figure 2A, siRNA targeting rec-8 was the only RNA-interference treatment that improved paraquat survival for strain SR708. This dsRNA-expressing construct extended survival by 17%, to 8.5 ± 0.3 [s.e.m.] h (Figure 2A; P < 0.01 by log-rank test), very close to that of mock-treated CL2a (8.3 ± 0.2 h; Figure 2B). In CL2a worms, however, rec-8 RNAi had no effect, as might be expected if the longer-lived lsq4 allele already expressed REC-8 at levels near optimal for adult survival. Conversely, RNAi to K09B11.5 (encoding a tyrosine protein kinase) reduced paraquat survival in the CL2a strain (Figure 2B; 25% decrease, P < 6E–5), to a greater extent than in SR708 (Figure 2A; 16%, P < 0.04). Although these data are consistent with a survival-curtailing role for K09B11.5 in view of its 5-fold higher expression in CL2a, they offer only weak support for a causal role because RNA interference often impairs robustness, presumably by disruption of diverse pathways.


Rec-8 dimorphism affects longevity, stress resistance and X-chromosome nondisjunction in C. elegans, and replicative lifespan in S. cerevisiae.

Ayyadevara S, Tazearslan C, Alla R, Jiang JC, Jazwinski SM, Shmookler Reis RJ - Front Genet (2014)

Rec-8 knockdown improves resistance to oxidative and thermal stresses, dependent on the lsq4–region background. Groups of 30 worms were fed on bacteria induced to express the indicated dsRNA (or empty expression vector) for 3 days from the L4/adult molt. They were then transferred to medium containing paraquat, and their subsequent survival monitored (see Methods). Of the indicated genes targeted by dsRNAs, only K09B11.5 had been found to be expressed at higher levels in CL2a, the longer-lived strain, and thus predicted to possibly reduce CL2a survival; the other 4 genes were expressed at higher levels in SR708, and thus were predicted to extend survival of treated SR708, if causal to the QTL effect on paraquat resistance. (A,B) Time courses of paraquat survival for control and dsRNA-treated adult worms, either (A) strain SR708, or (B) strain CL2a. (C,D). Paraquat dose-response curves for control vs. dsRNA-treated adults of strain (C) strain SR708, or (D) strain CL2a. (E,F) Thermotolerance survivals following abrupt transfer of standard survival plates from 20 to 35.5°C, containing control or dsRNA-treated adults of (E) strain SR708, or (F) strain CL2a. Each panel for heat-shock survival shows combined results from two independent experiments (solid and dashed lines indicate experiments 1 and 2, respectively). All panels show data representative of 2–4 experiments of each type.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4120681&req=5

Figure 2: Rec-8 knockdown improves resistance to oxidative and thermal stresses, dependent on the lsq4–region background. Groups of 30 worms were fed on bacteria induced to express the indicated dsRNA (or empty expression vector) for 3 days from the L4/adult molt. They were then transferred to medium containing paraquat, and their subsequent survival monitored (see Methods). Of the indicated genes targeted by dsRNAs, only K09B11.5 had been found to be expressed at higher levels in CL2a, the longer-lived strain, and thus predicted to possibly reduce CL2a survival; the other 4 genes were expressed at higher levels in SR708, and thus were predicted to extend survival of treated SR708, if causal to the QTL effect on paraquat resistance. (A,B) Time courses of paraquat survival for control and dsRNA-treated adult worms, either (A) strain SR708, or (B) strain CL2a. (C,D). Paraquat dose-response curves for control vs. dsRNA-treated adults of strain (C) strain SR708, or (D) strain CL2a. (E,F) Thermotolerance survivals following abrupt transfer of standard survival plates from 20 to 35.5°C, containing control or dsRNA-treated adults of (E) strain SR708, or (F) strain CL2a. Each panel for heat-shock survival shows combined results from two independent experiments (solid and dashed lines indicate experiments 1 and 2, respectively). All panels show data representative of 2–4 experiments of each type.
Mentions: Paraquat exposure constitutes a toxic oxidative stress, through generation of superoxide radical (Ebert et al., 1993, 1996; Ayyadevara et al., 2001, 2003; Shmookler Reis et al., 2007). As illustrated in Figure 2A, siRNA targeting rec-8 was the only RNA-interference treatment that improved paraquat survival for strain SR708. This dsRNA-expressing construct extended survival by 17%, to 8.5 ± 0.3 [s.e.m.] h (Figure 2A; P < 0.01 by log-rank test), very close to that of mock-treated CL2a (8.3 ± 0.2 h; Figure 2B). In CL2a worms, however, rec-8 RNAi had no effect, as might be expected if the longer-lived lsq4 allele already expressed REC-8 at levels near optimal for adult survival. Conversely, RNAi to K09B11.5 (encoding a tyrosine protein kinase) reduced paraquat survival in the CL2a strain (Figure 2B; 25% decrease, P < 6E–5), to a greater extent than in SR708 (Figure 2A; 16%, P < 0.04). Although these data are consistent with a survival-curtailing role for K09B11.5 in view of its 5-fold higher expression in CL2a, they offer only weak support for a causal role because RNA interference often impairs robustness, presumably by disruption of diverse pathways.

Bottom Line: A single gene in this interval is now shown to modulate all lsq4-associated traits.Full-genome analysis of transcript levels indicates that lsq4 contains a dimorphic gene governing the expression of many sperm-specific genes, suggesting an effect on spermatogenesis.Fourteen "dual-candidate" genes, implicated by both position and expression, were tested for RNA-interference effects on QTL-linked traits.

View Article: PubMed Central - PubMed

Affiliation: Central Arkansas Veterans Healthcare System, VA Medical Center Little Rock, AR, USA ; Department of Geriatrics, University of Arkansas for Medical Sciences Little Rock, AR, USA.

ABSTRACT
A quantitative trait locus (QTL) in the nematode C. elegans, "lsq4," was recently implicated by mapping longevity genes. QTLs for lifespan and three stress-resistance traits coincided within a span of <300 kbp, later narrowed to <200 kbp. A single gene in this interval is now shown to modulate all lsq4-associated traits. Full-genome analysis of transcript levels indicates that lsq4 contains a dimorphic gene governing the expression of many sperm-specific genes, suggesting an effect on spermatogenesis. Quantitative analysis of allele-specific transcripts encoded within the lsq4 interval revealed significant, 2- to 15-fold expression differences for 10 of 33 genes. Fourteen "dual-candidate" genes, implicated by both position and expression, were tested for RNA-interference effects on QTL-linked traits. In a strain carrying the shorter-lived allele, knockdown of rec-8 (encoding a meiotic cohesin) reduced its transcripts 4-fold, to a level similar to the longer-lived strain, while extending lifespan 25-26%, whether begun before fertilization or at maturity. The short-lived lsq4 allele also conferred sensitivity to oxidative and thermal stresses, and lower male frequency (reflecting X-chromosome non-disjunction), traits reversed uniquely by rec-8 knockdown. A strain bearing the longer-lived lsq4 allele, differing from the short-lived strain at <0.3% of its genome, derived no lifespan or stress-survival benefit from rec-8 knockdown. We consider two possible explanations: high rec-8 expression may include increased "leaky" expression in mitotic cells, leading to deleterious destabilization of somatic genomes; or REC-8 may act entirely in germ-line meiotic cells to reduce aberrations such as non-disjunction, thereby blunting a stress-resistance response mediated by innate immunity. Replicative lifespan was extended 20% in haploid S. cerevisiae (BY4741) by deletion of REC8, orthologous to nematode rec-8, implying that REC8 disruption of mitotic-cell survival is widespread, exemplifying antagonistic pleiotropy (opposing effects on lifespan vs. reproduction), and/or balancing selection wherein genomic disruption increases genetic variation under harsh conditions.

No MeSH data available.


Related in: MedlinePlus