Potassium accumulation characteristics and expression of related genes involved in potassium metabolism in a high-potassium variety: tobacco (Nicotiana tabacum) as a model.

We investigated potassium (K) accumulation characteristics and expression of K metabolism related genes in one high-K variety (ND202) and a common variety (NC89) of tobacco (Nicotiana tabacum L.). Results showed that K accumulation and leaf K content in ND202 were higher than those in NC89. The distribution rate and K accumulation in the leaves of ND202 increased significantly, while the distribution rate in the roots and stems had lower values. In addition, the maximum K accumulation rate and high-speed K accumulation duration in ND202 were found to be better than those in NC89. The expression of NKT1 in the upper and middle leaves of ND202 had an advantage, and the relative expression of NtKC1 and NtTPK1 in both the upper and middle leaves, as well as the roots, was also significantly upregulated. Conversely, the expression of NTRK1 in the lower leaves and roots of ND202 was weaker. ND202 had significantly greater expression levels of NtHAK1 than NC89 in the upper and middle leaves and roots; moreover, the expression of NtKT12 in the upper leaves and roots of ND202 was also higher. In comparison with common varieties, high-K varieties had a stronger ability to absorb and accumulate K. They also possessed higher expression of K+ channel- and transporter-related genes and showed a superior K accumulation rate and longer duration of high-speed K accumulation. Furthermore, K accumulation rate at 40-60days can be suggested as an important reference for the selection of high-K tobacco varieties.

Effect of Xeroderma pigmentosum complementation group F polymorphisms on gastric cancer risk and associations with H.pylori infection.

We conducted a hospital case-control study by genotyping four potential functional single nucleotide polymorphisms (SNPs) to assess the association of Xeroderma pigmentosum complementation group F (XPF) with gastric cancer susceptibility, and role of XPF polymorphisms in combination with H.pylori infection in risk definition. A total of 331 patients with gastric cancer and 355 controls were collected. Four SNPs of XPF, rs180067, rs1799801, rs2276466 and rs744154, were genotyped by Taqman real-time PCR method with a 7900 HT sequence detector system. The gastric cancer patients were more likely to have smoking habit, a family history of cancer and H.pylori infection. We did not find any significant difference in the genotype distributions of XPF rs180067, rs1799801, rs2276466 and rs744154 between cases and controls. However, multivariate logistic analysis showed a non-significant decreased risk in patients carrying rs180067 G allele, rs1799801 T allele or rs2276466 T allele genotypes. A non-significant increased risk of gastric cancer was found in individuals carrying the rs744154 GG genotype. Stratification by H.pylori infection and smoking was not significantly different in polymorphisms of XPF rs180067, rs1799801, rs2276466 and rs744154. The four XPF SNPs did not show significant interaction with H.pylori infection and smoking status (P for interaction was 0.35 and 0.18, respectively). Our study indicated that polymorphisms in rs180067, rs1799801, rs2276466 and rs744154 may affect the risk of gastric cancer but further large sample size studies are needed to validate any association.

DNA methylation polymorphism in flue-cured tobacco and candidate markers for tobacco mosaic virus resistance.

DNA methylation plays an important role in the epigenetic regulation of gene expression during plant growth, development, and polyploidization. However, there is still no distinct evidence in tobacco regarding the distribution of the methylation pattern and whether it contributes to qualitative characteristics. We studied the levels and patterns of methylation polymorphism at CCGG sites in 48 accessions of allotetraploid flue-cured tobacco, Nicotiana tabacum, using a methylation-sensitive amplified polymorphism (MSAP) technique. The results showed that methylation existed at a high level among tobacco accessions, among which 49.3% sites were methylated and 69.9% allelic sites were polymorphic. A cluster analysis revealed distinct patterns of geography-specific groups. In addition, three polymorphic sites significantly related to tobacco mosaic virus (TMV) resistance were explored. This suggests that tobacco breeders should pay more attention to epigenetic traits.