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• In heading Chinese cabbage, significant heterosis was observed in the growth period and yield-related traits, which represents a comprehensive advantage in the breeding. • The phenotype of parental inbred lines may be useful for predicting heterosis because it is rapid and simple, but the genetic distance calculated by SNP markers led to a moderate improvement in heterotic prediction. • Genetic distance calculated by homozygous differential SNPs was a better predictor of heterosis and F 1 performance than that calculated by total SNPs. Chinese cabbage (Brassica rapa L. ssp. Pekinensis) is the most widely consumed leafy vegetable in Asia. Most commercial cultivars are F 1 hybrids with high yield and good quality. To increase the breeding efficiency, heterotic prediction of hybrid performance was studied. Fourteen parental lines of Chinese cabbage were studied in a half-diallel cross to produce 91 hybrids. The average mid-parent heterosis (MPH) for 14 agronomic traits ranged from −5.07% to 106.76%, while the average high-parent heterosis (HPH) ranged from −109.90% to 80.56%. Significant HPH was observed in the growth period (−109.90%), biomass (80.56%), and plant weight (15.20%), which exhibited comprehensive advantages in breeding. Two methods were used to calculate the genetic distance (GD) between the parents based on 2,444,676 single nucleotide polymorphisms (SNPs): total SNPs (GD total) and homozygous differential SNPs (GD homo). Parental clustering based on total SNPs divided the parents into three major types, namely "flat-topped", "ovate", and "cylindrical". These types were more suitable for their traditional pedigree relationships. The correlation between the GD, mean parental phenotype, and heterosis indicated that the phenotype of the parental inbred lines may be useful for predicting heterosis because it is rapid and simple, whereas GD calculated using SNP markers led to a moderate improvement in heterotic prediction. GD homo was a better predictor of heterosis and F 1 performance than GD total. These results confirmed that whole-genome SNP markers are an effective tool for evaluating GD in Chinese cabbage and are useful for parent selection in breeding. [ABSTRACT FROM AUTHOR]

Main Conclusion: Gene co-expression network analysis of the heat-responsive core transcriptome in two contrasting Brassica rapa accessions reveals the main metabolic pathways, key modules and hub genes, are involved in long-term heat stress. Brassica rapa is a widely cultivated and economically important vegetable in Asia. High temperature is a common stress that severely impacts leaf head formation in B. rapa, resulting in reduced quality and production. The purpose of this study was thus to identify candidate heat tolerance genes by comparative transcriptome analysis of two contrasting B. rapa accessions in response to long-term heat stress. Two B. rapa accessions, '268' and '334', which showed significant differences in heat tolerance, were used for RNA sequencing analysis. We identified a total of 11,055 and 8921 differentially expressed genes (DEGs) in '268' and '334', respectively. Functional enrichment analyses of all of the identified DEGs, together with the genes identified from weighted gene co-expression network analyses (WGCNA), revealed that the autophagy pathway, glutathione metabolism, and ribosome biogenesis in eukaryotes were significantly up-regulated, whereas photosynthesis was down-regulated, in the heat resistance of B. rapa '268'. Furthermore, when B. rapa '334' was subjected to long-term high-temperature stress, heat stress caused significant changes in the expression of certain functional genes linked to protein processing in the endoplasmic reticulum and plant hormone signal transduction pathways. Autophagy-related genes might have been induced by persistent heat stress and remained high during recovery. Several hub genes like HSP17.6, HSP17.6B, HSP70-8, CLPB1, PAP1, PYR1, ADC2, and GSTF11 were discussed in this study, which may be potential candidates for further analyses of the response to long-term heat stress. These results should help elucidate the molecular mechanisms of heat stress adaptation in B. rapa.

Although approximately 20 common genetic susceptibility loci have been identified for breast cancer risk through genome-wide association studies (GWASs), genetic risk variants reported to date explain only a small fraction of heritability for this common cancer. We conducted a four-stage GWAS including 17 153 cases and 16 943 controls among East-Asian women to search for new genetic risk factors for breast cancer. After analyzing 684 457 SNPs in 2062 cases and 2066 controls (Stage I), we selected for replication among 5969 Chinese women (4146 cases and 1823 controls) the top 49 SNPs that had neither been reported previously nor were in strong linkage disequilibrium with reported SNPs (Stage II). Three SNPs were further evaluated in up to 13 152 Chinese and Japanese women (6436 cases and 6716 controls) (Stage III). Finally, two SNPs were evaluated in 10 847 Korean women (4509 cases and 6338 controls) (Stage IV). SNP rs10822013 on chromosome 10q21.2, located in the zinc finger protein 365 (ZNF365) gene, showed a consistent association with breast cancer risk in all four stages with a combined per-risk allele odds ratio of 1.10 (95% CI: 1.07-1.14) (P-value for trend = 5.87 × 10(-9)). In vitro electrophoretic mobility shift assays demonstrated the potential functional significance of rs10822013. Our results strongly implicate rs10822013 at 10q21.2 as a genetic risk variant for breast cancer among East-Asian women.