Genome-Wide Association Analysis of the Genetic Basis for Sheath Blight Resistance in Rice.

BACKGROUND: Sheath blight (ShB), caused by Rhizoctonia solani Kühn, is one of the most destructive rice diseases. Developing ShB-resistant rice cultivars represents the most economical and environmentally sound strategy for managing ShB. RESULTS: To characterize the genetic basis for ShB resistance in rice, we conducted association studies for traits related to ShB resistance, namely culm length (CL), lesion height (LH), and relative lesion height (RLH). Combined a single locus genome-wide scan and a multi-locus method using 2,977,750 single-nucleotide polymorphisms to analyse 563 rice accessions, we detected 134, 562, and 75 suggestive associations with CL, LH, and RLH, respectively. The adjacent signals associated with RLH were merged into 27 suggestively associated loci (SALs) based on the estimated linkage disequilibrium blocks. More than 44% of detected RLH-SALs harboured multiple QTLs/genes associated with ShB resistance, while the other RLH-SALs were putative novel ShB resistance loci. A total of 261 ShB resistance putative functional genes were screened from 23 RLH-SALs according to bioinformatics and haplotype analyses. Some of the annotated genes were previously reported to encode defence-related and pathogenesis-related proteins, suggesting that quantitative resistance to ShB in rice is mediated by SA- and JA-dependent signalling pathways. CONCLUSIONS: Our findings may improve the application of germplasm resources as well as knowledge-based ShB management and the breeding of ShB-resistant rice cultivars.

[Expression of autophagy-related protein Beclin-1 and microtubule-associated protein 2 light chain 3 in periodontal ligament cells in orthodontic tooth pressure areas].

OBJECTIVE: To investigate the expression of autophagy-related protein Beclin-1 and microtubule-associated protein 2 light chain 3 (LC3Ⅱ) in periodontal ligament cells in orthodontic tooth pressure areas. METHODS: Sixty male SD rats were randomly divided into a blank control group and nine experimental groups. In the experimental groups, 0.392 N orthodontic force was used to move the first right upper molars for 15 min, 30 min, 1 h, 2 h, 4 h, 12 h, 1 d, 3 d, or 7 d. The blank control group did not receive any treatment. The rats were euthanized. Changes in the morphology of the periodontal membrane in the pressure areas were observed through hematoxylin and eosin (HE) staining. The expression levels of Beclin-1 and LC3Ⅱ were detected by immunohistochemical staining, and tartrate-resistant acid phosphatase (TRAP) staining was performed for the counting of osteoclasts. RESULTS: The HE stains showed that the hyalinization of the periodontal ligament appeared in the pressure areas after 1 day of exertion and was gradually aggravated. The immunohistochemical stains showed that the expression levels of Beclin-1 and LC3Ⅱ in the experimental groups gradually increased, peaked after 1 h, and then gradually decreased. The expression levels peaked again after 1 d, then decreased to baseline levels at 7 d of exertion. Beclin-1 and LC3Ⅱ were expressed in the osteoclasts. The TRAP stains indicated that the number of osteoclasts started to increase after 1 day. CONCLUSIONS: Autophagy may participate in the process of periodontal ligament reconstruction in orthodontic tooth pressure areas by mediating the hyalinization of periodontal ligament and affecting the biological effects of osteoclasts.

Reduction in arsenic intake from water has different impacts on lung cancer and bladder cancer in an arseniasis endemic area in Taiwan.

BACKGROUND: Excessive arsenic intake has a detrimental effect on human health, as reflected in an increase in cancer incidence. In an area on the southwest coast of Taiwan, arsenic intake from well water since the 1920s had caused an exceptionally high mortality from cancer. Municipal water has become available to people living in the arseniasis endemic area since the early 1970s. This study explored the impacts of reduction in arsenic intake from water on lung cancer and bladder cancer in the arseniasis endemic area in Taiwan. METHODS: Chart records of 23,013 patients diagnosed with bladder cancer and 93,633 patients with lung cancer from 1979 to 2003 were retrieved from the Taiwan Cancer Registry Center. We used the age-period-cohort model to study the changes in the incidence of lung cancer and bladder cancer in the arseniasis endemic area and the rest of Taiwan. RESULTS: Three decades after municipal water supply to the arseniasis and black foot disease endemic area (BFDEA), we saw a marked decrease in the incidence of both bladder cancer and lung cancer in the area, especially for those in the later cohorts. The relative risk (RR) of getting a bladder cancer for people living in BFDEA when compared with those in the rest of Taiwan has dropped from 20 for the early cohorts to 5 for the late cohorts. As to lung cancer, the RR has decreased from 8 to between 1.5 and 2. CONCLUSION: Reduction in arsenic intake from water has a positive impact on the incidence of both lung and bladder cancer; however, while RR for lung cancer has dropped to below 2, RR for bladder cancer remained at around 5. The difference may be because (1) there are other risk factors beside the well-water intake or (2) bladder cancer may have longer latency period for excessive arsenic exposure than lung cancer. More studies are required to understand the causes behind the difference in RR for these two types of cancer.