Expression of genes related to tolerance to low temperature for maize seed germination.

The aim of this study was to characterize maize lines tolerant to cold temperatures during the germination process. Seeds from lines with different levels of tolerance to low temperatures were used; 3 lines were classified as tolerant and 3 as susceptible to low germination temperatures. A field was set up to multiply seeds from selected lines. After the seeds were harvested and classified, we conducted physiological tests and analyzed fatty acid content of palmitic, stearic, oleic, linoleic, linolenic, and eicosenoic acids. In proteomic analysis, the expression of heat-resistant proteins, including catalase, peroxidase, esterase, superoxide dismutase, and α-amylase, were evaluated. Transcript analysis was used to measure the expression of the genes AOX1, AOX2, ZmMPK-17, and ZmAN-13. The material showing the highest susceptibility to low germination temperatures contained high saturated fatty acid content. Expression of α-amylase in seeds soaked for 72 h at a temperature of 10°C was lower than expression of α-amylase when soaked at 25°C for the same amount of time. We observed variation in the expression of heat-resistant proteins in seeds of the lines evaluated. The genes AOX and Zm-AN13 were promising for use in identifying maize materials that are tolerant to low germination temperatures.

Verification and characterization of chromosome duplication in haploid maize.

Doubled haploid technology has been used by various private companies. However, information regarding chromosome duplication methodologies, particularly those concerning techniques used to identify duplication in cells, is limited. Thus, we analyzed and characterized artificially doubled haploids using microsatellites molecular markers, pollen viability, and flow cytometry techniques. Evaluated material was obtained using two different chromosome duplication protocols in maize seeds considered haploids, resulting from the cross between the haploid inducer line KEMS and 4 hybrids (GNS 3225, GNS 3032, GNS 3264, and DKB 393). Fourteen days after duplication, plant samples were collected and assessed by flow cytometry. Further, the plants were transplanted to a field, and samples were collected for DNA analyses using microsatellite markers. The tassels were collected during anthesis for pollen viability analyses. Haploid, diploid, and mixoploid individuals were detected using flow cytometry, demonstrating that this technique was efficient for identifying doubled haploids. The microsatellites markers were also efficient for confirming the ploidies preselected by flow cytometry and for identifying homozygous individuals. Pollen viability showed a significant difference between the evaluated ploidies when the Alexander and propionic-carmin stains were used. The viability rates between the plodies analyzed show potential for fertilization.

Comparison of the effects of two resistance training regimens on muscular and bone responses in premenopausal women.

SUMMARY: A 28-week resistance training with linear periodization was compared with an undulating model in 27 premenopausal women. In both groups, bone mineral density (BMD) was not changed but muscle strength increased, and there were changes in anthropometrical and muscle damage parameters, indicating that in this population, these models are similar concerning these variables. INTRODUCTION: This study seeks to compare the effects of resistance training with undulating versus linear periodization on BMD, muscle strength, anthropometrical variables, and muscle damage parameters in premenopausal women. METHODS: Twenty-seven females (39.6 +/- 0.41 years, mean +/- standard error), without osteopenia or osteoporosis and without calcium supplementation, were randomly assigned either to a linear periodization group (LPG, n = 14) or to an undulating periodization group (UPG, n = 13). The subjects were trained three times a week for 28 weeks. Lumbar spine and femoral neck BMDs were measured through dual-energy X-ray absorptiometry. Maximal and submaximal dynamic muscle strengths were measured through the 1-RM and 20-RM tests, respectively. Anthropometrical (body mass, skinfolds, and perimeters) and muscle damage parameters were assessed through serum creatine kinase (CK) and delayed-onset muscle soreness (DOMS). RESULTS: BMD remained unchanged in both groups, despite significant increases in maximal (LPG, 37-73%; UPG, 40-70%) and submaximal (LPG, 82-114%; UPG, 70-102%) muscle strength. The perimeter of the distal thigh was increased (about 1.7 cm) in both groups. CK and DOMS were greater in the first mesocycle than in the subsequent ones. After the 1st training session in each mesocycle, 24 and 48 h CK was increased as compared to pretraining values. CONCLUSIONS: The resistance training of 28 weeks increased muscle strength in both training groups with no difference in BMD or in the occurrence of muscle damage.