Genetic Polymorphisms of DNA Repair Gene: XRCC1 Pro206Pro and Gln632Gln in a Chinese Han Population

DNA repair genes are increasingly studied because of their critical role in maintaining genome integrity. The base excision repair (BER) pathway is a DNA repair pathway that operates on small lesions, such as oxidized or reduced bases, fragmented or nonbulky adducts, or those produced by methylating agents. The XRCC1 polymorphic system is the key gene of the BER pathway. In this study, polymorphisms of XRCC1 Pro206Pro on exon 7 and Gln632Gln on exon 17 were analyzed in a northeastern Chinese Han population. Genomic DNA extracted from 303 unrelated individuals and the PCR-RFLP technique were used to identify variants. The allele frequencies were 0.90 (A) and 0.10 (G) for XRCC1 Pro206Pro and 0.88 (G) and 0.12 (A) for XRCC1 Gln632Gln. The genotype frequencies were 0.797 (AA), 0.203 (AG), and 0 (GG) for XRCC1 Pro206Pro and 0.007 (AA), 0.222 (AG), and 0.771 (GG) for XRCC1 Gln632Gln. The expected heterozygosity and PIC were 18 and 16.38% for Pro206Pro and 21.12 and 18.89% for Gln632Gln. The two polymorphisms were in strong linkage disequilibrium (D' = 0.921, r (2) = 0.735). The results are compared with those of other reported populations. They showed marked ethnic group differences. This study provides the first analysis of the distribution of allele frequency for XRCC1 Pro206Pro and Gln632Gln in a Chinese population.     

N enrichment affects the arbuscular mycorrhizal fungi-mediated relationship between a C4 grass and a legume

Arbuscular mycorrhizal fungi (AMF) regulate soil nutrient cycling, directly supplying a host plant with nitrogen (N). AMF can also affect the outcome of interspecific interactions, but a mechanistic understanding of how soil N availability affects AMF-mediated interspecific relationships is currently lacking. We selected one dominant (Bothriochloa ischaemum; C₄ grass) and one subordinate (Lespedeza davurica; legume) species in a natural grassland climax community to investigate the mechanism by which AMF influence interspecific interaction (mixed and monoculture) under three levels of N addition (0, low, and high N addition). Under the non-N addition treatment, AMF preferentially supplied N to the roots of B. ischaemum at the expense of N uptake by L. davurica, resulting in inhibited AMF benefits for L. davurica shoot growth. Under the low N addition treatment, interspecific interaction via AMF promoted L. davurica growth. Compared to the non-N addition treatment, N addition largely mitigated the effects, both positive (for B. ischaemum) and negative (for L. davurica), of AMF-mediated interspecific interaction on plant N uptake via AMF. When soil N availability severely limited plant growth, preferential N supply to the C₄ grass by AMF was important for maintaining the abundance of the dominant species. When the N limitation for plant growth was alleviated by N addition, the interaction between AMF and soil microorganisms improved nutrient availability for the legume by stimulating activity of the enzyme responsible for soil organic matter mineralization, which is important for maintaining the abundance of the subordinate species. These data could influence strategies for maintaining biodiversity.     

HapMap-based study of a region encompassing ERCC1 and ERCC2 related to lung cancer susceptibility in a Chinese population

DNA repair genes play a crucial role in carcinogenesis. The paper aims to explore if common variants in ERCC1 are involved in lung cancer susceptibility. A Chinese case-control study included 339 lung cancer cases and 358 controls using five haplotype-tagging SNPs (htSNPs) (rs3212980, rs3212964, rs3212961, rs11615 and rs2298881) from the HapMap database, capturing 95% of the common haplotypic diversity of ERCC1. A combined analysis of eleven htSNPs covering ERCC2 and ERCC1 was performed. No significant association between individual htSNPs and lung cancer susceptibility was observed. There were interactions between rs3212961 and rs2298881and smoking duration (P=0.03 and P=0.01, respectively). Thus, the variant alleles of rs3212961 [OR (95% CI)=1.81(1.03-3.17), P=0.04] and rs2298881 [OR (95% CI)=2.16(1.26-3.70), P=0.005] were associated with risk of lung cancer among long-term smokers (>20 years) but not among never smokers and short-term smokers. No significant associations with lung cancer susceptibility were observed for global or individual haplotypes defined by five htSNPs of ERCC1. A highly differential distribution of haplotypes based on eleven htSNPs covering ERCC2 and ERCC1 were found (global test P=4.3×10(-5)). After Bonferroni correction, haplotypeER2+1-1 [OR (95% CI)=3.63 (1.39-9.47), P=0.005, marginally] and haplotypeER2+1-8 [OR (95% CI)=4.46 (2.03-9.79), P=5.6×10(-5), strongly] were associated with increased risk of lung cancer. The diplotype analysis with haplotypeER2+1-8 was also statistically significant (P<0.001). Haplotype analysis of pathological subtypes revealed that htSNPs of both genes may mainly influence the risk of lung adenocarcinoma. Strong linkage disequilibrium exist in two regions encompassing ERCC2 and ERCC1. These data suggest that common genetic variations in ERCC1 may influence increased risk of smoking-related lung cancer and one of the causative effectors may locate around or within ERCC2.     

Different responses of scleractinian coral Acropora pruinosa from Weizhou Island during extreme high temperature events

Ecological surveys observe coral “winners” and “losers” in global coral bleaching events. However, the key contributors to holobiont tolerance and interactions between symbionts remain unclear. Herein, we compared bleaching and unbleaching Acropora pruinosa corals from Weizhou Island, during an extreme high-temperature event in the northern South China Sea in 2020. We found the dominant Symbiodiniaceae subclade in the bleaching and unbleaching corals to be C1; however, the density of Symbiodiniaceae in the latter was significantly higher than that in the former. Additionally, the symbiotic bacteria α diversity in the unbleaching coral was significantly higher than that in the bleaching coral, with a reorganized bacterial community structure. Core microbiome analyses revealed 55 bacterial core operational taxonomic units (OTUs), of which 10 were significantly differentially enriched between the two coral groups. The significantly enriched bacterial core OTUs in the unbleaching coral were primarily nitrogen cycling related, while those enriched in the bleaching coral were associated with antimicrobial activity. RNA-Seq analyses revealed that significantly upregulated genes in the bleaching coral were primarily associated with diseases and autophagy, while those in the unbleaching coral were associated with immune defense and maintenance of the symbiotic relationship between corals and symbionts. We propose that the differences in tolerance of A. pruinosa result from the cooperation between coral host, Symbiodiniaceae, and symbiotic bacteria. In extreme high-temperature events, unbleaching corals may maintain stable symbiotic relationships by increasing the diversity of symbiotic bacteria, regulating the structure of the symbiotic bacteria community, improving the interaction between coral host and symbiont and enhancing host immunity, thus avoiding coral bleaching. This study illuminates the relationship between the coral symbiont and tolerance differences of coral holobionts, providing new insights for further exploration into the adaptability of scleractinian corals in the context of global warming.

     

Biosynthesis of the earthy odorant geosmin by a bifunctional Streptomyces coelicolor enzyme

Geosmin is responsible for the characteristic odor of moist soil, as well as off-flavors in drinking water and foodstuffs. Geosmin is generated from farnesyl diphosphate (FPP, 2) by an enzyme that is encoded by the SCO6073 gene in the soil organism Streptomyces coelicolor A32 (ref. 3). We have now shown that the recombinant N-terminal half of this protein catalyzes the Mg2+-dependent cyclization of FPP to germacradienol and germacrene D, while the highly homologous C-terminal domain, previously thought to be catalytically silent, catalyzes the Mg2+-dependent conversion of germacradienol to geosmin. Site-directed mutagenesis confirmed that the N- and C-terminal domains each harbor a distinct, independently functioning active site. A mutation in the N-terminal domain of germacradienol-geosmin synthase of a catalytically essential serine to alanine results in the conversion of FPP to a mixture of sesquiterpenes that includes an aberrant product identified as isolepidozene, which was previously suggested to be an enzyme-bound intermediate in the cyclization of FPP to germacradienol.     

Polymorphisms of DNA Repair Genes: ERCC1 G19007A and ERCC2/XPD C22541A in a Northeastern Chinese Population

DNA repair systems are responsible for maintaining the integrity of the genome and have a critical role in protecting against mutations that can lead to cancer. DNA repair gene products of ERCC1 and ERCC2/XPD are involved in the nucleotide excision repair pathway. The allele frequencies of the polymorphisms ERCC1 G19007A and ERCC2/XPD C22541A were examined in a northeastern Chinese population. The allele frequencies were 0.21 (A) and 0.79 (G) for ERCC1 G19007A and 0.49 (A) and 0.51 (C) for ERCC2/XPD C22541A. Comparison with average frequencies from previously reported Caucasian studies demonstrated that the A-allele frequency of ERCC1 G19007A was much lower in the northeastern Chinese population, indicating a remarkable ethnic difference (chi((1)) (2) = 160.09, p < 0.001), and that allele frequencies of ERCC2/XPD C22541A showed marginal racial differences (chi((1)) (2) = 4.36, p = 0.04). We have previously reported that both homozygote carriers of the A-allele as well as homozygous carriers of a high-risk haplotype (which includes the AA genotype in ERCC1 G19007A) were at increased risk of basal cell carcinoma, breast cancer, and lung cancer among Caucasians. The low A-allele frequency of ERCC1 G19007A in the Chinese population may suggest that the genetic contribution to cancer risk differs substantially between ethnic groups.     

去除基部果枝对不同基因型棉花部分早衰特征的影响

以9个不同基因型棉花(GossypiumL.)为材料,通过去除基部2个果枝调节源库比例,研究在生殖生长初期调节源库比例对不同基因型棉花部分早衰特征的影响。结果显示:(1)在生殖生长初期调节源库比例对供试9个棉花品种的冠层底部光合有效辐射(TPAR)、叶面积系数(LAI)、不同结铃期所结棉铃对位果枝叶SPAD值变化率、棉铃脱落率、红茎比率及单铃重均有较大的影响,处理间差异达到显著(P<0.05)或极显著(P<0.01)水平,且随着生育进程的推进,去除基部果枝对延缓早衰的作用更为显著。(2)对于不同基因型棉花,改变生殖生长初期源库比例延缓早衰的效应存在一定差异,去除基部果枝对于‘冀杂999’、‘国抗34’和‘荃银2号’3个品种早衰现象的延缓效应最好,而‘川杂棉33’居中,‘鲁HB标杂-1’等5个品种延缓效应较差。研究表明,在生殖生长初期去除基部果枝对棉花早衰有延缓作用,其效应大小在棉花基因型间存在差异。