Vector Transmission of Tomato Yellow Leaf Curl Thailand Virus by the Whitefly Bemisia tabaci: Circulative or Propagative?

Viruses that cause tomato yellow leaf curl disease are part of a group of viruses of the genus Begomovirus, family Geminiviridae. Tomato-infecting begomoviruses cause epidemics in tomato crops in tropical, subtropical, and Mediterranean climates, and they are exclusively transmitted by Bemisia tabaci in the field. The objective of the present study was to examine the transmission biology of the tomato yellow leaf curl Thailand virus (TYLCTHV) by B. tabaci, including virus-infected tissues, virus translocation, virus replication, and transovarial transmission. The results demonstrated that the virus translocates from the alimentary gut to the salivary glands via the hemolymph, without apparent replication when acquired by B. tabaci. Furthermore, the virus was detected in 10% of the first-generation progeny of viruliferous females, but the progeny was unable to cause the viral infection of host plants. There was no evidence of transovarial transmission of TYLCTHV in B. tabaci. When combined with the current literature, our results suggest that B. tabaci transmits TYLCTHV in a persistent-circulative mode. The present study enhances our understanding of virus–vector interaction and the transmission biology of TYLCTHV in B. tabaci.

Allelism Test between Crosses of High-O/L x High-O/L and Very High-O/L x Very High-O/L Peanut Genotypes

ABSTRACT Crosses were made between High-O/L x High-O/L and between Very High-O/L x Very High-O/L peanut genotypes. The High-O/L parental genotypes were F435-OL-2 and ‘Flavor Runner 458’ and ranged between 20 and 40:1 oleic (O) to linoleic (L) fatty acid methyl ester ratio. The Very High-O/L parental cultivars were ‘Georgia Hi-O/L' and ‘Georgia-11J' and consistently had O/L ratios ≥40:1 over four years at the Tifton, Georgia location when grown under maximum-input production practices with irrigation. F1 plants from the High-O/L x High-O/L cross combination had an average O/L ratio of 32.5:1; whereas, the F1 plants from the Very High-O/L x Very High-O/L crosses had an average O/L ratio of 50:1. Average O/L ratios of both F2 and F3 generation progeny also had similar O/L ratios within High-O/L x High-O/L and Very High-O/L x Very High-O/L crosses. The results from these test crosses suggest that there are at least two different high-oleic genotypes possibly associated with either multiple alleles or modifier genes.

Impact of mothers' early life exposure to low or high folate on progeny outcome and DNA methylation patterns

The dynamic patterning of DNA and histone methylation during oocyte development presents a potentially susceptible time for epigenetic disruption due to early life environmental exposure of future mothers. We investigated whether maternal exposure to folic acid deficient and supplemented diets starting in utero could affect oocytes and cause adverse developmental and epigenetic effects in next generation progeny. Female BALB/c mice (F0) were placed on one of four amino acid defined diets for 4 weeks before pregnancy and throughout gestation and lactation: folic acid control (rodent recommended daily intake; Ctrl), 7-fold folic acid deficient, 10-fold folic acid supplemented or 20-fold folic acid supplemented diets. F1 female pups were weaned onto Ctrl diets, mated to produce the F2 generation and the F2 offspring were examined at E18.5 for developmental and epigenetic abnormalities. Resorption rates were increased and litter sizes decreased amongst F2 E18.5-day litters in the 20-fold folic acid supplemented group. Increases in abnormal embryo outcomes were observed in all three folic acid deficient and supplemented groups. Subtle genome-wide DNA methylation alterations were found in the placentas and brains of F2 offspring in the 7-fold folic acid deficient , 10-fold folic acid supplemented and 20-fold folic acid supplemented groups; in contrast, global and imprinted gene methylation were not affected. The findings show that early life female environmental exposures to both low and high folate prior to oocyte maturation can compromise oocyte quality, adversely affecting offspring of the next generation, in part by altering DNA methylation patterns.

Evolved changes in breathing and CO2 sensitivity in deer mice native to high altitudes

We examined the control of breathing by O2 and CO2 in deer mice native to high altitude to help uncover the physiological specializations used to cope with hypoxia in high-altitude environments. Highland deer mice ( Peromyscus maniculatus) and lowland white-footed mice ( P. leucopus) were bred in captivity at sea level. The first and second generation progeny of each population was raised to adulthood and then acclimated to normoxia or hypobaric hypoxia (12 kPa O2, simulating hypoxia at ~4,300 m) for 6–8 wk. Ventilatory responses to poikilocapnic hypoxia (stepwise reductions in inspired O2) and hypercapnia (stepwise increases in inspired CO2) were then compared between groups. Both generations of lowlanders appeared to exhibit ventilatory acclimatization to hypoxia (VAH), in which hypoxia acclimation enhanced the hypoxic ventilatory response and/or made the breathing pattern more effective (higher tidal volumes and lower breathing frequencies at a given total ventilation). In contrast, hypoxia acclimation had no effect on breathing in either generation of highlanders, and breathing was generally similar to hypoxia-acclimated lowlanders. Therefore, attenuation of VAH may be an evolved feature of highlanders that persists for multiple generations in captivity. Hypoxia acclimation increased CO2 sensitivity of breathing, but in this case, the effect of hypoxia acclimation was similar in highlanders and lowlanders. Our results suggest that highland deer mice have evolved high rates of alveolar ventilation that are unaltered by exposure to chronic hypoxia, but they have preserved ventilatory sensitivity to CO2.

Gestational stress, placental norepinephrine transporter and offspring fertility

Chronic cold stress produces adrenergic overload that can affect fetal development. The placental norepinephrine transporter (NET) clears norepinephrine (NE) from both maternal circulation and the fetus during gestation. If this system fails, NE clearance can be reduced, leading to high fetal exposure to NE. The main aim of this study was to determine the changes in NET expression during gestation and their relationship with the functional capacity of NET to transport NE under stressful conditions. Additionally, this study correlated these findings with the reproductive capacity of 2nd-generation progeny. Pregnant rats were subjected to chronic cold stress at 4°C for 3 h each day throughout their pregnancies. We found that exposure of pregnant rats to sympathetic stress caused the following effects: increased NE and corticosterone levels throughout pregnancy, decreased capacity of the placenta to clear NE from the fetus to the mother’s circulation, altered NET protein levels depending on the sex of the fetus and increased placental and body weights of pups. For the first time, we also described the disrupted fertility of progeny as adults. Increased NE plasma levels during pregnancy under sympathetic stress conditions correlated with decreased NET functionality that provoked changes in the development of progeny and their fertility in adulthood.

Genetic parameters of growth and stem quality traits for jack pine second-generation progeny tested in New Brunswick

Genetic variation and time trends for growth and stem quality traits were evaluated in jack pine (Pinus banksiana Lamb.) second-generation progeny tests. The study was based on a large dataset, involving 275 half-sib families and 17 field trials, planted across New Brunswick, Canada. Growth was indicated by cumulative tree height (HT) measured at trial ages from 5 to 20 years, and stem quality was evaluated on stem straightness (SST) and stem forking (SF). Results indicated that both HT and SST were moderately genetically controlled, with mean individual heritability estimates of 0.14 (range: 0.03–0.30) and 0.16 (range: 0.10–0.25), respectively, which were lower than those estimates from the first-generation progeny tests. Heritability estimates for HT increased from trial ages of 5 to 10 years and then remained stable, whereas for SST, heritability estimates showed a “Λ” shape with the highest value occurring at trial age of 15 years. HT measurements at trial ages of 5 to 10 years were highly predictive of HT growth at 15 to 20 years, and similarly, SST assessment at 10 years correlated well with assessment at 20 years. Estimates of genetic correlation between HT and SST were positively and moderately strong, which contrasted with the moderately negative genetic correlation between the two traits in the first-generation progeny. Heritability estimates for SF were generally low (mean [Formula: see text] = 0.06) and remained constant over time. SF was essentially not genetically correlated with HT or SST. Family-by-site interactions were weak for HT and SST over the trial ages but were strong for SF at trial age of 10 years or older. The potential impact of selection on genetic architecture of growth and stem quality traits in advanced generation jack pine breeding populations and on breeding and selection strategies was discussed.