Helena Oakey

Effect of Treatment of Gestational Diabetes Mellitus on Obesity in the Next Generation

OBJECTIVE Gestational diabetes mellitus (GDM) may cause obesity in the offspring. The objective was to assess the effect of treatment for mild GDM on the BMI of 4- to 5-year-old children. RESEARCH DESIGN AND METHODS Participants were 199 mothers who participated in a randomized controlled trial of the treatment of mild GDM during pregnancy and their children. Trained nurses measured the height and weight of the children at preschool visits in a state-wide surveillance program in the state of South Australia. The main outcome measure was age- and sex-specific BMI Z score based on standards of the International Obesity Task Force. RESULTS At birth, prevalence of macrosomia (birth weight ≥4,000 g) was 5.3% among the 94 children whose mothers were in the intervention group, and 21.9% among the 105 children in the routine care control group. At 4- to 5-years-old, mean (SD) BMI Z score was 0.49 (1.20) in intervention children and 0.41 (1.40) among controls. The difference between treatment groups was 0.08 (95% CI −0.29 to 0.44), an estimate minimally changed by adjustment for maternal race, parity, age, and socio-economic index (0.08 [−0.29 to 0.45]). Evaluating BMI ≥85th percentile rather than continuous BMI Z score gave similarly null results. CONCLUSIONS Although treatment of GDM substantially reduced macrosomia at birth, it did not result in a change in BMI at age 4- to 5-years-old.

Joint modeling of additive and non-additive genetic line effects in single field trials

A statistical approach is presented for selection of best performing lines for commercial release and best parents for future breeding programs from standard agronomic trials. The method involves the partitioning of the genetic effect of a line into additive and non-additive effects using pedigree based inter-line relationships, in a similar manner to that used in animal breeding. A difference is the ability to estimate non-additive effects. Line performance can be assessed by an overall genetic line effect with greater accuracy than when ignoring pedigree information and the additive effects are predicted breeding values. A generalized definition of heritability is developed to account for the complex models presented.

Joint modeling of additive and non-additive (genetic line) effects in multi-environment trials.

A statistical approach for the analysis of multi-environment trials (METs) is presented, in which selection of best performing lines, best parents, and best combination of parents can be determined. The genetic effect of a line is partitioned into additive, dominance and residual non-additive effects. The dominance effects are estimated through the incorporation of the dominance relationship matrix, which is presented under varying levels of inbreeding. A computationally efficient way of fitting dominance effects is presented which partitions dominance effects into between family dominance and within family dominance line effects. The overall approach is applicable to inbred lines, hybrid lines and other general population structures where pedigree information is available.

Effect of paternal heat stress on the development in vitro of preimplantation embryos in the mouse

Summary.  This study was conducted to investigate the effects of paternal heat stress on the development in vitro of preimplantation embryos in the mouse. Female C57/CBA mice were superovulated using eCG/hCG and mated either to an untreated (control) male mouse or to one that had been exposed for 24 h to an ambient temperature of 36 ± 0.1 °C and 62 ± 0.4% relative humidity, between 3 and 42 days previously. Putative zygotes were collected from the oviducts of mated mice, 25–28 h after hCG injection, and cultured in vitro. Embryo development was evaluated at 24‐h intervals for up to 120 h. Paternal heat stress significantly reduced the proportion of embryos that developed normally during 24–120 h of in vitro culture, when zygotes were sired by males which had been heat stressed between 7 and 35 days prior to mating. Maximum impairment to development (including nondevelopment, abnormal and dying/dead embryos) occurred in those embryos sired by males at days 14 and 21 after heating. Embryo development returned to control levels by day 42 after heat stress. Furthermore, whilst all stages of embryo development were affected by paternal heat stress, the proportion of embryos at the two‐cell stage appeared to be most severely affected. Four‐cell to morula stages and the morula to blastocyst stage also demonstrated impairment at days 14, 21, 28 and 35 after heating. These results demonstrate that a single episode of paternal heat stress significantly reduces the development of preimplantation embryos, and this is not recovered until day 42 after heating. The present results also support previous work demonstrating that sperm from the epididymis as well as germ cells in the testis are susceptible to damage by heat stress, with both spermatids and spermatocytes being the most vulnerable.

Maternal and neonatal outcomes following induction of labor: a cohort study

Objective. To evaluate maternal and neonatal outcomes associated with birth at term by week of gestational age and also by onset of labor. Design. Cohort study. Setting. A state‐wide perinatal outcome database. Population. 28 626 women with spontaneous onset of labor, induction of labor for recognized indications and induction of labor for non‐recognized indications. Methods. Cohort study utilizing a validated dataset comparing outcomes with type of onset of labor using a log binomial model. Main outcome measures. Cesarean section, assisted vaginal birth, important measures of maternal and neonatal morbidity. Results. Induction of labor for non‐recognized indications was associated with a significantly increased risk of a range of outcomes, including cesarean section (RR 1.67, 95%CI 1.55–1.80). The lowest risk of adverse maternal and infant outcome occurred with birth between 38 and 39 weeks and with the spontaneous onset of labor. Conclusions. Induction of labor for non‐recognized indications at term is associated with an increased risk of adverse outcomes. Caution is warranted with a liberal policy of induction of labor at term in an otherwise uncomplicated pregnancy.

Salinity tolerance loci revealed in rice using high-throughput non-invasive phenotyping

High-throughput phenotyping produces multiple measurements over time, which require new methods of analyses that are flexible in their quantification of plant growth and transpiration, yet are computationally economic. Here we develop such analyses and apply this to a rice population genotyped with a 700k SNP high-density array. Two rice diversity panels, indica and aus, containing a total of 553 genotypes, are phenotyped in waterlogged conditions. Using cubic smoothing splines to estimate plant growth and transpiration, we identify four time intervals that characterize the early responses of rice to salinity. Relative growth rate, transpiration rate and transpiration use efficiency (TUE) are analysed using a new association model that takes into account the interaction between treatment (control and salt) and genetic marker. This model allows the identification of previously undetected loci affecting TUE on chromosome 11, providing insights into the early responses of rice to salinity, in particular into the effects of salinity on plant growth and transpiration.

Protection of grapevine pruning wounds from infection by Eutypa lata using Trichoderma harzianum and Fusarium lateritium

Abstract.Trichoderma harzianum applied to grapevine pruning wounds in a spore suspension and in the commercial formulations of Trichoseal, Trichoseal spray and Vinevax pruning wound dressing reduced recovery of Eutypa lata in the glasshouse and in the field. Recovery of E. lata was significantly reduced (P < 0.001) when fresh wounds were treated with viable T. harzianum 2 or 7 days before inoculation with ascospores of the pathogen in the glasshouse. In field experiments, recovery of E. lata was significantly reduced (P < 0.001) when fresh pruning wounds were treated with spores of T. harzianum, Fusarium lateritium or Vinevax 1 or 14 days before ascospores were applied. In general, a delay of 14 days between wounding and inoculation with ascospores of E. lata reduced recovery of the pathogen compared with inoculation on the day after wounding.

The effect of temperature on the male and female recombination landscape of barley

Barley (Hordeum vulgare) is a crop of global significance. However, a third of the genes of barley are largely inaccessible to conventional breeding programmes as crossovers are localised to the ends of the chromosomes. This work examines whether crossovers can be shifted to more proximal regions simply by elevating growth temperature. We utilised a genome-wide marker set for linkage analysis combined with cytological mapping of crossover events to examine the recombination landscape of plants grown at different temperatures. We found that barley shows heterochiasmy, that is, differences between female and male recombination frequencies. In addition, we found that elevated temperature significantly changes patterns of recombination in male meiosis only, with a repositioning of Class I crossovers determined by cytological mapping of HvMLH3 foci. We show that the length of synaptonemal complexes in male meiocytes increases in response to temperature. The results demonstrate that the distribution of crossover events are malleable and can be shifted to proximal regions by altering the growth temperature. The shift in recombination is the result of altering the distribution of Class I crossovers, but the higher recombination at elevated temperatures is potentially not the result of an increase in Class I events.

The Synaptonemal Complex Protein ZYP1 Is Required for Imposition of Meiotic Crossovers in Barley

The number of genetic crossovers during meiosis, and the potential for creating novel variation, is influenced by the ZYP1 protein. When ZYP1 is depleted in Arabidopsis, fewer crossovers occur, whereas in rice, more crossovers have been reported. Here, we show that barley plants with very reduced amounts of ZYP1 make far fewer crossovers, although the localization of crossovers is not affected. In many cereal crops, meiotic crossovers predominantly occur toward the ends of chromosomes and 30 to 50% of genes rarely recombine. This limits the exploitation of genetic variation by plant breeding. Previous reports demonstrate that chiasma frequency can be manipulated in plants by depletion of the synaptonemal complex protein ZIPPER1 (ZYP1) but conflict as to the direction of change, with fewer chiasmata reported in Arabidopsis thaliana and more crossovers reported for rice (Oryza sativa). Here, we use RNA interference (RNAi) to reduce the amount of ZYP1 in barley (Hordeum vulgare) to only 2 to 17% of normal zygotene levels. In the ZYP1RNAi lines, fewer than half of the chromosome pairs formed bivalents at metaphase and many univalents were observed, leading to chromosome nondisjunction and semisterility. The number of chiasmata per cell was reduced from 14 in control plants to three to four in the ZYP1-depleted lines, although the localization of residual chiasmata was not affected. DNA double-strand break formation appeared normal, but the recombination pathway was defective at later stages. A meiotic time course revealed a 12-h delay in prophase I progression to the first labeled tetrads. Barley ZYP1 appears to function similarly to ZIP1/ZYP1 in yeast and Arabidopsis, with an opposite effect on crossover number to ZEP1 in rice, another member of the Poaceae.

Genomic Selection in Multi-environment Crop Trials

Genomic selection in crop breeding introduces modeling challenges not found in animal studies. These include the need to accommodate replicate plants for each line, consider spatial variation in field trials, address line by environment interactions, and capture nonadditive effects. Here, we propose a flexible single-stage genomic selection approach that resolves these issues. Our linear mixed model incorporates spatial variation through environment-specific terms, and also randomization-based design terms. It considers marker, and marker by environment interactions using ridge regression best linear unbiased prediction to extend genomic selection to multiple environments. Since the approach uses the raw data from line replicates, the line genetic variation is partitioned into marker and nonmarker residual genetic variation (i.e., additive and nonadditive effects). This results in a more precise estimate of marker genetic effects. Using barley height data from trials, in 2 different years, of up to 477 cultivars, we demonstrate that our new genomic selection model improves predictions compared to current models. Analyzing single trials revealed improvements in predictive ability of up to 5.7%. For the multiple environment trial (MET) model, combining both year trials improved predictive ability up to 11.4% compared to a single environment analysis. Benefits were significant even when fewer markers were used. Compared to a single-year standard model run with 3490 markers, our partitioned MET model achieved the same predictive ability using between 500 and 1000 markers depending on the trial. Our approach can be used to increase accuracy and confidence in the selection of the best lines for breeding and/or, to reduce costs by using fewer markers.