SMDT1 variants impair EMRE-mediated mitochondrial calcium uptake in patients with muscle involvement

Ionic calcium (Ca2+) is a key messenger in signal transduction and its mitochondrial uptake plays an important role in cell physiology. This uptake is mediated by the mitochondrial Ca2+ uniporter (MCU), which is regulated by EMRE (essential MCU regulator) encoded by the SMDT1 (single-pass membrane protein with aspartate rich tail 1) gene. This work presents the genetic, clinical and cellular characterization of two patients harbouring SMDT1 variants and presenting with muscle problems. Analysis of patient fibroblasts and complementation experiments demonstrated that these variants lead to absence of EMRE protein, induce MCU subcomplex formation and impair mitochondrial Ca2+ uptake. However, the activity of oxidative phosphorylation enzymes, mitochondrial morphology and membrane potential, as well as routine/ATP-linked respiration were not affected. We hypothesize that the muscle-related symptoms in the SMDT1 patients result from aberrant mitochondrial Ca2+ uptake.

Uncoupled evolution of the Polycomb system and deep origin of non-canonical PRC1

Polycomb group proteins, as part of the Polycomb repressive complexes, are essential in gene repression through chromatin compaction by canonical PRC1, mono-ubiquitylation of histone H2A by non-canonical PRC1 and tri-methylation of histone H3K27 by PRC2. Despite prevalent models emphasizing tight functional coupling between PRC1 and PRC2, it remains unclear whether this paradigm indeed reflects the evolution and functioning of these complexes. Here, we conduct a comprehensive analysis of the presence or absence of cPRC1, nPRC1 and PRC2 across the entire eukaryotic tree of life, and find that both complexes were present in the Last Eukaryotic Common Ancestor (LECA). Strikingly, ~42% of organisms contain only PRC1 or PRC2, showing that their evolution since LECA is largely uncoupled. The identification of ncPRC1-defining subunits in unicellular relatives of animals and fungi suggests ncPRC1 originated before cPRC1, and we propose a scenario for the evolution of cPRC1 from ncPRC1. Together, our results suggest that crosstalk between these complexes is a secondary development in evolution.

One gene versus two: a regional study on the efficacy of single gene versus pyramided resistance for soybean aphid management

The soybean aphid (Aphis glycines Matsumura) is a threat to soybean production in the Midwestern United States. Varieties containing the Rag1 soybean aphid resistance gene have been released with limited success in reducing aphid populations. Furthermore, virulent biotypes occur within North America and challenge the durability of single-gene resistance. Pyramiding resistance genes has the potential to improve aphid population suppression and increase resistance gene durability. Our goal was to determine if a pyramid could provide improved aphid population suppression across awide range of environments. We conducted a small-plot field experiment across seven states and three years. We compared soybean near-isolines for the Rag1 or Rag2 gene, and a pyramid line containing both genes for their ability to decrease aphid pressure and protect yield compared with a susceptible line. These lines were evaluated both with and without a neonicitinoid seed treatment. All aphid-resistant lines significantly decreased aphid pressure at all locations but one. The pyramid line experienced lower aphid pressure than both single-gene lines at eight of 23 location-years. Soybean aphids significantly reduced soybean yield for the susceptible line by 14% and for both single-gene lines by 5%; however, no significant yield decrease was observed for the pyramid line. The neonicitinoid seed treatment reduced plant exposure to aphids across all soybean lines, but did not provide significant yield protection for any of the lines. These results demonstrate that pyramiding resistance genes can provide sufficient and consistent yield protection from soybean aphid in North America.

Economic threshold for soybean aphid (Hemiptera: Aphididae)

Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), reached damaging levels in 2003 and 2005 in soybean, Glycine max (L.) Merrill, in most northern U.S. states and Canadian provinces, and it has become one of the most important pests of soybean throughout the North Central region. A common experimental protocol was adopted by participants in six states who provided data from 19 yield-loss experiments conducted over a 3-yr period. Population doubling times for field populations of soybean aphid averaged 6.8 d +/- 0.8 d (mean +/- SEM). The average economic threshold (ET) over all control costs, market values, and yield was 273 +/- 38 (mean +/- 95% confidence interval [CI], range 111-567) aphids per plant. This ET provides a 7-d lead time before aphid populations are expected to exceed the economic injury level (EIL) of 674 +/- 95 (mean +/- 95% CI, range 275-1,399) aphids per plant. Peak aphid density in 18 of the 19 location-years occurred during soybean growth stages R3 (beginning pod formation) to R5 (full size pod) with a single data set having aphid populations peaking at R6 (full size green seed). The ET developed here is strongly supported through soybean growth stage R5. Setting an ET at lower aphid densities increases the risk to producers by treating an aphid population that is growing too slowly to exceed the EIL in 7 d, eliminates generalist predators, and exposes a larger portion of the soybean aphid population to selection by insecticides, which could lead to development of insecticide resistance.

Economic threshold for soybean aphid (Hemiptera: Aphididae)

Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), reached damaging levels in 2003 and 2005 in soybean, Glycine max (L.) Merrill, in most northern U.S. states and Canadian provinces, and it has become one of the most important pests of soybean throughout the North Central region. A common experimental protocol was adopted by participants in six states who provided data from 19 yield-loss experiments conducted over a 3-yr period. Population doubling times for field populations of soybean aphid averaged 6.8 d +/- 0.8 d (mean +/- SEM). The average economic threshold (ET) over all control costs, market values, and yield was 273 +/- 38 (mean +/- 95% confidence interval [CI], range 111-567) aphids per plant. This ET provides a 7-d lead time before aphid populations are expected to exceed the economic injury level (EIL) of 674 +/- 95 (mean +/- 95% CI, range 275-1,399) aphids per plant. Peak aphid density in 18 of the 19 location-years occurred during soybean growth stages R3 (beginning pod formation) to R5 (full size pod) with a single data set having aphid populations peaking at R6 (full size green seed). The ET developed here is strongly supported through soybean growth stage R5. Setting an ET at lower aphid densities increases the risk to producers by treating an aphid population that is growing too slowly to exceed the EIL in 7 d, eliminates generalist predators, and exposes a larger portion of the soybean aphid population to selection by insecticides, which could lead to development of insecticide resistance.

Dietary ascorbic acid and selenium relationships in the guinea pig

Plasma-, erythrocyte- and liver Se-dependent glutathione peroxidase (GPx) activity, ascorbic acid (AA) concentration, and erythrocyte and liver Se levels were analyzed in groups of guinea pigs fed a Torula yeast-based semipurified diet supplemented with either O (-AA), 200 (+AA), or 400 (++AA) mg of AA/kg of diet and either 0.05 (+Se) or 0.2 (++Se) ppm of Se for 24 days. Plasma, erythrocyte, and liver AA concentration were directly related to the levels of AA fed. There were 21.2 +/- 2.7% and 51.2 +/- 4.5% (p less than 0.0001) increases in erythrocyte and liver Se, respectively, in ++Se guinea pigs compared to +Se guinea pigs. Dietary AA had no effect on erythrocyte or liver Se levels. Plasma, erythrocyte, and liver GPx specific activities were significantly (p less than 0.001) increased in ++Se guinea pigs compared to +Se guinea pigs. In addition, liver, plasma, and erythrocyte GPx activities were directly related to the level of AA fed. These data indicate that dietary AA has no influence on tissue levels of Se but increases plasma, liver, and erythrocyte GPx activities in the guinea pig.