Evaluation of Genetic Diversity and Population Structure Analysis among Germplasm of Agaricus bisporus by SSR Markers

Agaricus bisporus is a popular edible mushroom that is cultivated worldwide. Due to its secondary homothallic nature, cultivated A. bisporus strains have low genetic diversity, and breeding novel strains is challenging. The aim of this study was to investigate the genetic diversity and population structure of globally collected A. bisporus strains using simple sequence repeat (SSR) markers. Agaricus bisporus strains were divided based on genetic distance-based groups and model-based subpopulations. The major allele frequency (MAF), number of genotypes (NG), number of alleles (NA), observed heterozygosity (HO), expected heterozygosity (HE), and polymorphic information content (PIC) were calculated, and genetic distance, population structure, genetic differentiation, and Hardy–Weinberg equilibrium (HWE) were assessed. Strains were divided into two groups by distance-based analysis and into three subpopulations by model-based analysis. Strains in subpopulations POP A and POP B were included in Group I, and strains in subpopulation POP C were included in Group II. Genetic differentiation between strains was 99%. Marker AB-gSSR-1057 in Group II and subpopulation POP C was confirmed to be in HWE. These results will enhance A. bisporus breeding programs and support the protection of genetic resources.

Evaluation of Genetic Diversity and Population Structure Analysis among Germplasm of Agaricus bisporus by SSR Markers

Agaricus bisporus is a popular edible mushroom that is cultivated worldwide. Due to its secondary homothallic nature, cultivated A. bisporus strains have low genetic diversity, and breeding novel strains is challenging. The aim of this study was to investigate the genetic diversity and population structure of globally collected A. bisporus strains using simple sequence repeat (SSR) markers. Agaricus bisporus strains were divided based on genetic distance-based groups and model-based subpopulations. The major allele frequency (MAF), number of genotypes (NG), number of alleles (NA), observed heterozygosity (HO), expected heterozygosity (HE), and polymorphic information content (PIC) were calculated, and genetic distance, population structure, genetic differentiation, and Hardy–Weinberg equilibrium (HWE) were assessed. Strains were divided into two groups by distance-based analysis and into three subpopulations by model-based analysis. Strains in subpopulations POP A and POP B were included in Group I, and strains in subpopulation POP C were included in Group II. Genetic differentiation between strains was 99%. Marker AB-gSSR-1057 in Group II and subpopulation POP C was confirmed to be in HWE. These results will enhance A. bisporus breeding programs and support the protection of genetic resources.

Molecular Characterization of 170 New gDNA-SSR Markers for Genetic Diversity in Button Mushroom (Agaricus bisporus)

We designed 170 new simple sequence repeat (SSR) markers based on the whole-genome sequence data of button mushroom (Agaricus bisporus), and selected 121 polymorphic markers. A total of 121 polymorphic markers, the average major allele frequency (M(AF)) and the average number of alleles (N(A)) were 0.50 and 5.47, respectively. The average number of genotypes (N(G)), observed heterozygosity (H(O)), expected heterozygosity (H(E)), and polymorphic information content (PIC) were 6.177, 0.227, 0.619, and 0.569, respectively. Pearson's correlation coefficient showed that M(AF) was negatively correlated with N(G) (−0.683), N(A) (−0.600), H(O) (−0.584), and PIC (−0.941). N(G), N(A), H(O), and PIC were positively correlated with other polymorphic parameters except for M(AF). UPGMA clustering showed that 26 A. bisporus accessions were classified into 3 groups, and each accession was differentiated. The 121 SSR markers should facilitate the use of molecular markers in button mushroom breeding and genetic studies.

Development of Electrical Neural Stimulator Generating Periodic and Non-periodic Signals and Supporting Closed-loop Experimental System

It is essential to build a system to generate proper neural stimulus signals with adjusting parameters. We developed a stimulator with up to four channels for separate settings in periodic and non-periodic modes. The device can support a closed-loop experimental system which utilizes neural information in real time as a feedback for controlling stimuli. To confirm whether stimulating signals are properly produced and delivered inside the brain, two experiments with rats were conducted. We observed that the change of firing rates and the cross-power spectral density increased after stimulation which meant that electric signals were transferred well and that they affected the neurons' activities. Thus, it is expected that the stimulator can be utilized to produce appropriate stimulation signals in accordance with various objectives.

Development of Polymorphic Simple Sequence Repeat Markers using High-Throughput Sequencing in Button Mushroom (Agaricus bisporus)

The white button mushroom (Agaricus bisporus) is one of the most widely cultivated species of edible mushroom. Despite its economic importance, relatively little is known about the genetic diversity of this species. Illumina paired-end sequencing produced 43,871,558 clean reads and 69,174 contigs were generated from five offspring. These contigs were subsequently assembled into 57,594 unigenes. The unigenes were annotated with reference genome in which 6,559 unigenes were associated with clusters, indicating orthologous genes. Gene ontology classification assigned many unigenes. Based on genome data of the five offspring, 44 polymorphic simple sequence repeat (SSR) markers were developed. The major allele frequency ranged from 0.42 to 0.92. The number of genotypes and the number of alleles ranged from 1 to 4, and from 2 to 4, respectively. The observed heterozygosity and the expected heterozygosity ranged from 0.00 to 1.00, and from 0.15 to 0.64, respectively. The polymorphic information content value ranged from 0.14 to 0.57. The genetic distances and UPGMA clustering discriminated offspring strains. The SSR markers developed in this study can be applied in polymorphism analyses of button mushroom and for cultivar discrimination.

Career exploration behavior of Korean medical students / 한국의학교육

PURPOSE: This study is to analyze the effects of medical students’ social support and career barriers on career exploration behavior mediated by career decision-making self-efficacy. METHODS: We applied the t-test to investigate the difference among the variables based on gender and admission types. Also, we performed path analysis to verify the effect of perceived career barriers and social support on career exploration behavior with career decision efficacy as a mediator. RESULTS: First, we noted statistically significant gender and admission type difference in social support, career barriers and career exploration behaviors. Second, social support and career barriers were found to influence career exploration behavior as a mediating variable for career decision-making self-efficacy. CONCLUSION: Social support and career barriers as perceived by medical students influenced their career exploration behavior, with their decision-making self-efficacy serving as a full mediator. Therefore, this study has educational implications for career program development and educational training for career decision-making self-efficacy.

Analysis of medical students' needs for development of a career guidance program / 한국의학교육

PURPOSE: The purpose of this study is to provide basic data for the development of a career guidance program through a demand survey. For this purpose, three study topics were examined: Is there a difference between the satisfaction and importance of a career program? Is there a difference between the satisfaction and importance of a career program by gender, grade level? and What type of mentor and the mentoring way of medical students demanded? METHODS: The subjects were 380 students at Seoul National University College of Medicine. The data were analyzed by frequency analysis, paired t-test, and Borich's formula. RESULTS: By t-test with matched samples for satisfaction-importance, We noted statistically significant differences in all domains. In particular, the difference was greater in the second year. According to the needs analysis, the most urgent program is meeting with seniors in various career areas. Also, medical students hope for mentor from clinical professors of the university and successful medical practitioners, and personal counseling. CONCLUSION: These results show that medical students need a career guidance program. The findings of the study can be used to guide the development of career education programs and curriculum for medicine students.