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Drosophila americana Diapausing Females Show Features Typical of Young Flies.

Reis M, Valer FB, Vieira CP, Vieira J - PLoS ONE (2015)

Bottom Line: Nevertheless, in the genus Drosophila, diapause is almost always associated with the cessation of ovarian development and reproductive activity in adult females.ActinD1 expression levels suggest that diapausing females are biologically much younger than their chronological age, and that the fly as a whole, rather than the ovarian development alone, which is phenotypically more evident, is delayed by diapause.Therefore, diapause candidate genes that show expression levels that are compatible with flies younger than their chronological age may not necessarily play a role in reproductive diapause and in adaptation to seasonally varying environmental conditions.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal; Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal.

ABSTRACT
Diapause is a period of arrested development which is controlled physiologically, preprogrammed environmentally and characterized by metabolic depression that can occur during any stage of insect development. Nevertheless, in the genus Drosophila, diapause is almost always associated with the cessation of ovarian development and reproductive activity in adult females. In this work, we show that, in D. americana (a temperate species of the virilis group), diapause is a genetically determined delay in ovarian development that is triggered by temperature and/or photoperiod. Moreover, we show that in this species diapause incidence increases with latitude, ranging from 13% in the southernmost to 91% in the northernmost range of the distribution. When exposed to diapause inducing conditions, both diapausing and non-diapausing females show a 10% increase in lifespan, that is further increased by 18.6% in diapausing females, although senescence is far from being negligible. ActinD1 expression levels suggest that diapausing females are biologically much younger than their chronological age, and that the fly as a whole, rather than the ovarian development alone, which is phenotypically more evident, is delayed by diapause. Therefore, diapause candidate genes that show expression levels that are compatible with flies younger than their chronological age may not necessarily play a role in reproductive diapause and in adaptation to seasonally varying environmental conditions.

No MeSH data available.


Related in: MedlinePlus

ActinD1 expression level can be used as a marker of ontogenetic delay, which results in extended LS, but it is not a marker of biological age.Differences in ActinD1 gene expression levels were determined between 28 days old diapausing females (O53-D), 15 days old (O53-15d) and control females (O53-C) reared for 28 days under non-diapause inducing conditions (12L:12D at 25°C), as well as between 28 days old non-diapausing females (CB05.08-ND), 20 days old (CB05.08-20d) and controls (CB05.08-C) reared for 28 days under non-diapause inducing conditions (12L:12D at 25°C). The reference gene RpL32 was used to normalize the expression values. Three biological replicates were used for each sample and the averages of the log-transformed values of 2-∆CT are presented with their respective S.E.M.. A two-tailed Student’s t test assuming equal variances was used to address if the averages of normalized ActinD1 expression levels of the different samples and treatments are significantly different (n.s. P > 0.05; * 0.05 > P > 0.01; ** 0.01 > P > 0.001; *** P < 0.001).
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pone.0138758.g006: ActinD1 expression level can be used as a marker of ontogenetic delay, which results in extended LS, but it is not a marker of biological age.Differences in ActinD1 gene expression levels were determined between 28 days old diapausing females (O53-D), 15 days old (O53-15d) and control females (O53-C) reared for 28 days under non-diapause inducing conditions (12L:12D at 25°C), as well as between 28 days old non-diapausing females (CB05.08-ND), 20 days old (CB05.08-20d) and controls (CB05.08-C) reared for 28 days under non-diapause inducing conditions (12L:12D at 25°C). The reference gene RpL32 was used to normalize the expression values. Three biological replicates were used for each sample and the averages of the log-transformed values of 2-∆CT are presented with their respective S.E.M.. A two-tailed Student’s t test assuming equal variances was used to address if the averages of normalized ActinD1 expression levels of the different samples and treatments are significantly different (n.s. P > 0.05; * 0.05 > P > 0.01; ** 0.01 > P > 0.001; *** P < 0.001).

Mentions: Given that LS is extended both in diapausing and in non-diapausing females reared under diapause inducing conditions, we hypothesized that flies under those conditions should have a gene expression pattern that is compatible with flies younger than their chronological age. Both in D. melanogaster and D. virilis (a species closely related to D. americana), Actin79B (known as ActinD1 in D. virilis; see [42]) expression levels drop dramatically with adult age. Thus, we hypothesized that the expression of this gene could be a marker of biological age. This gene is expressed at high levels in the TDT (tergal depressor of the trochanter) muscle and in some other tubular muscles of the legs both in D. melanogaster [46] and in D. virilis [42]. Moreover, there is very little or even no expression in ovaries (modENCODE project ([47]; Flybase.org)). Therefore, ActinD1 expression levels are independent of the oocyte stages which are used to characterize a female fly as diapausing or non-diapausing. Our results indicate that, as expected, in D. americana, ActinD1 expression is highest in newborn females followed by diapausing individuals, non-diapausing individuals reared under diapause inducing conditions and finally in individuals reared under 12L:12D at 25°C (Fig 4). When ActinD1 expression levels of females reared under diapause and non-diapause inducing conditions are plotted against the average LS determined in the previous section, 94% of the variation is explained (R2 = 0.94; P < 0.001; Fig 5). Thus, also as expected, the ActinD1 expression levels accurately reflect the observed differences in LS. According to the ageing slowdown rates estimated in the previous section, after 28 days under 10L:14D at 11°C, O53 diapausing and CB05.08 non-diapausing females should be of the same biological age as 15 and 20 days old females reared under 12L:12D at 25°C, respectively. Nevertheless, the expression levels of 15 days old O53 females and 20 days old CB05.08 females reared under non-diapause inducing conditions are significantly lower (Student’s t test; P < 0.01) than those from females reared under diapause inducing conditions. They are, however, not statistically different from 28 days old controls (Fig 6). Thus, the slowing down in the rate of ontogenetic development induced by the diapause inducing conditions and diapause per se (reflected in the ActinD1 expression levels), is greater than the slowdown in the ageing rate. Compatible with the ontogenetic delay caused by diapause inducing conditions, as well as by diapause per se, is the observation made in this work that, in D. americana, ovaries are smaller when both diapausing and non-diapausing flies are exposed to diapause inducing conditions, and that diapausing females have the smallest ovaries. Since, ActinD1 shows very little or even no expression in ovaries, the observed ontogenetic delay must affect the fly as a whole.


Drosophila americana Diapausing Females Show Features Typical of Young Flies.

Reis M, Valer FB, Vieira CP, Vieira J - PLoS ONE (2015)

ActinD1 expression level can be used as a marker of ontogenetic delay, which results in extended LS, but it is not a marker of biological age.Differences in ActinD1 gene expression levels were determined between 28 days old diapausing females (O53-D), 15 days old (O53-15d) and control females (O53-C) reared for 28 days under non-diapause inducing conditions (12L:12D at 25°C), as well as between 28 days old non-diapausing females (CB05.08-ND), 20 days old (CB05.08-20d) and controls (CB05.08-C) reared for 28 days under non-diapause inducing conditions (12L:12D at 25°C). The reference gene RpL32 was used to normalize the expression values. Three biological replicates were used for each sample and the averages of the log-transformed values of 2-∆CT are presented with their respective S.E.M.. A two-tailed Student’s t test assuming equal variances was used to address if the averages of normalized ActinD1 expression levels of the different samples and treatments are significantly different (n.s. P > 0.05; * 0.05 > P > 0.01; ** 0.01 > P > 0.001; *** P < 0.001).
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Related In: Results  -  Collection

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pone.0138758.g006: ActinD1 expression level can be used as a marker of ontogenetic delay, which results in extended LS, but it is not a marker of biological age.Differences in ActinD1 gene expression levels were determined between 28 days old diapausing females (O53-D), 15 days old (O53-15d) and control females (O53-C) reared for 28 days under non-diapause inducing conditions (12L:12D at 25°C), as well as between 28 days old non-diapausing females (CB05.08-ND), 20 days old (CB05.08-20d) and controls (CB05.08-C) reared for 28 days under non-diapause inducing conditions (12L:12D at 25°C). The reference gene RpL32 was used to normalize the expression values. Three biological replicates were used for each sample and the averages of the log-transformed values of 2-∆CT are presented with their respective S.E.M.. A two-tailed Student’s t test assuming equal variances was used to address if the averages of normalized ActinD1 expression levels of the different samples and treatments are significantly different (n.s. P > 0.05; * 0.05 > P > 0.01; ** 0.01 > P > 0.001; *** P < 0.001).
Mentions: Given that LS is extended both in diapausing and in non-diapausing females reared under diapause inducing conditions, we hypothesized that flies under those conditions should have a gene expression pattern that is compatible with flies younger than their chronological age. Both in D. melanogaster and D. virilis (a species closely related to D. americana), Actin79B (known as ActinD1 in D. virilis; see [42]) expression levels drop dramatically with adult age. Thus, we hypothesized that the expression of this gene could be a marker of biological age. This gene is expressed at high levels in the TDT (tergal depressor of the trochanter) muscle and in some other tubular muscles of the legs both in D. melanogaster [46] and in D. virilis [42]. Moreover, there is very little or even no expression in ovaries (modENCODE project ([47]; Flybase.org)). Therefore, ActinD1 expression levels are independent of the oocyte stages which are used to characterize a female fly as diapausing or non-diapausing. Our results indicate that, as expected, in D. americana, ActinD1 expression is highest in newborn females followed by diapausing individuals, non-diapausing individuals reared under diapause inducing conditions and finally in individuals reared under 12L:12D at 25°C (Fig 4). When ActinD1 expression levels of females reared under diapause and non-diapause inducing conditions are plotted against the average LS determined in the previous section, 94% of the variation is explained (R2 = 0.94; P < 0.001; Fig 5). Thus, also as expected, the ActinD1 expression levels accurately reflect the observed differences in LS. According to the ageing slowdown rates estimated in the previous section, after 28 days under 10L:14D at 11°C, O53 diapausing and CB05.08 non-diapausing females should be of the same biological age as 15 and 20 days old females reared under 12L:12D at 25°C, respectively. Nevertheless, the expression levels of 15 days old O53 females and 20 days old CB05.08 females reared under non-diapause inducing conditions are significantly lower (Student’s t test; P < 0.01) than those from females reared under diapause inducing conditions. They are, however, not statistically different from 28 days old controls (Fig 6). Thus, the slowing down in the rate of ontogenetic development induced by the diapause inducing conditions and diapause per se (reflected in the ActinD1 expression levels), is greater than the slowdown in the ageing rate. Compatible with the ontogenetic delay caused by diapause inducing conditions, as well as by diapause per se, is the observation made in this work that, in D. americana, ovaries are smaller when both diapausing and non-diapausing flies are exposed to diapause inducing conditions, and that diapausing females have the smallest ovaries. Since, ActinD1 shows very little or even no expression in ovaries, the observed ontogenetic delay must affect the fly as a whole.

Bottom Line: Nevertheless, in the genus Drosophila, diapause is almost always associated with the cessation of ovarian development and reproductive activity in adult females.ActinD1 expression levels suggest that diapausing females are biologically much younger than their chronological age, and that the fly as a whole, rather than the ovarian development alone, which is phenotypically more evident, is delayed by diapause.Therefore, diapause candidate genes that show expression levels that are compatible with flies younger than their chronological age may not necessarily play a role in reproductive diapause and in adaptation to seasonally varying environmental conditions.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal; Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal.

ABSTRACT
Diapause is a period of arrested development which is controlled physiologically, preprogrammed environmentally and characterized by metabolic depression that can occur during any stage of insect development. Nevertheless, in the genus Drosophila, diapause is almost always associated with the cessation of ovarian development and reproductive activity in adult females. In this work, we show that, in D. americana (a temperate species of the virilis group), diapause is a genetically determined delay in ovarian development that is triggered by temperature and/or photoperiod. Moreover, we show that in this species diapause incidence increases with latitude, ranging from 13% in the southernmost to 91% in the northernmost range of the distribution. When exposed to diapause inducing conditions, both diapausing and non-diapausing females show a 10% increase in lifespan, that is further increased by 18.6% in diapausing females, although senescence is far from being negligible. ActinD1 expression levels suggest that diapausing females are biologically much younger than their chronological age, and that the fly as a whole, rather than the ovarian development alone, which is phenotypically more evident, is delayed by diapause. Therefore, diapause candidate genes that show expression levels that are compatible with flies younger than their chronological age may not necessarily play a role in reproductive diapause and in adaptation to seasonally varying environmental conditions.

No MeSH data available.


Related in: MedlinePlus