Substitution mapping of QTLs controlling seed dormancy using single segment substitution lines derived from multiple cultivated rice donors in seven cropping seasons.

KEY MESSAGE: A permanent advanced population containing 388 SSSLs was used for genetic analysis of seed dormancy; 25 QTLs including eight stable, six major and five new were identified. Seed dormancy (SD) is not only a complex biological phenomenon, but also a key practical problem in agricultural production closely related with pre-harvest sprouting (PHS). However, the genetic mechanisms of SD remain elusive. Here, we report the genetic dissection of SD in rice using 388 single segment substitution lines (SSSLs) derived from 16 donor parents. Continuous variation and positive correlations in seed germination percentages were observed in seven seasons. Genetic analysis revealed the narrow sense heritability in different seasons varied from 31.4 to 82.2% with an average value of 56.8%. In addition, 49 SSSLs exhibited significant difference to recipient parent HJX74 on SD in at least two seasons, and 12 of them were stably identified with putative QTLs in all of their corresponding cropping seasons. Based on substitution mapping, a total of 25 dormancy QTLs were detected on 11 chromosomes except the chromosome 5 with an interval length of 1.1 to 31.3 cM. The additive effects of these QTLs changed from -0.31 to -0.13, and the additive effect contributions ranged from 16.7 to 41.4%. Six QTLs, qSD3-2, qSD4-1, qSD7-1, qSD7-2, qSD7-3 and qSD11-2, showed large additive effect contributions (≥30%). Five QTLs, qSD3-3, qSD7-1, qSD7-4, qSD9-1 and qSD10-1, may represent novel ones. Furthermore, linkage and recombinant analysis delimited qSD7-1 to a locus 1.5 cM away from marker Oi2 and a 355-kb fragment flanked by RM1134 and Ui159, respectively. Taken together, this work conducts a comprehensive genetic dissection of SD and will provide more selections for breeding elite PHS-resistant rice varieties.

Induced expression of the IER5 gene by gamma-ray irradiation and its involvement in cell cycle checkpoint control and survival.

The immediate-early response gene 5 (IER5) was previously shown, using microarray analysis, to be upregulated by ionizing radiation. Here we further characterized the dose- and time-dependency of radiation-induced expression of IER5 at doses from 0.5 to 15 Gy by quantitative real-time PCR analyses in HeLa cells and human lymphoblastoid AHH-1 cells. A radiation-induced increase in the IER5 mRNA level was evident 2 h after irradiation with 2 Gy in both cell lines. In AHH-1 cells the expression reached a peak at 4 h and then quickly returned to the control level, while in HeLa cells the expression only remained increased for a short period of time at around 2 h after irradiation before returning to the control. After high-dose irradiation (10 Gy), the induction of the IER5 expression was lower and delayed in AHH-1 cells as compared with 2-Gy irradiated cells. In HeLa cells, at this dose, two peaks of increased expression were observed 2 h and 12-24 h post-irradiation, respectively. RNA interference technology was employed to silence the IER5 gene in HeLa cells. siRNA-mediated suppression of IER5 resulted in an increased proliferation of HeLa cells. Cell growth and survival analyses demonstrated that suppression of IER5 significantly increased the radioresistance of HeLa cells to radiation doses of up to 6 Gy, but barely affected the sensitivity of cells at 8 Gy. Moreover, suppression of IER5 potentiated radiation-induced arrest at the G2-M transition and led to an increase in the fraction of S phase cells. Taken together, we propose that the early radiation-induced expression of IER5 affects the radiosensitivity via disturbing radiation-induced cell cycle checkpoints.

Induction of apoptosis and autophagic cell death by the vanillin derivative 6-bromine-5-hydroxy-4-methoxybenzaldehyde is accompanied by the cleavage of DNA-PKcs and rapid destruction of c-Myc oncoprotein in HepG2 cells.

Autophagy is a regulated lysosomal pathway involving the bulk degradation of cytoplasmic contents, and is an emerging attractive therapeutic approach for treating cancers. In the present study, we demonstrates that bromovanin (6-bromine-5-hydroxy-4-methoxybenzaldehyde), a vanillin derivative, exhibits a potent antiproliferative effect on a broad spectrum of cancer cell lines, but it induces apoptosis with a large variation in extent on different cancer cell lines. Ultrastructural observation in transmission electron microscopy reveals that autophagy is another type of cell death induced by bromovanin in HepG2 cells. Treatment with bromovanin significantly increases cellular ROS level as well as elicits DNA double-strand breaks as indicated by comet assay and the increased phosphorylated H2AX. Cleavage and inactivation of DNA-PKcs induced by bromovanin is found to occur concurrently with a rapid destruction of c-Myc oncoprotein. These multiple effects of bromovanin, especially the induction of both apoptosis and autophagy, make it very appealing for the development as a novel anticancer drug.

Characterization of a novel effect of hPinX1 on hTERT nucleolar localization.

The factor PinX1 has been shown as a telomerase inhibitor evolutionarily conserved in both the yeast and the human being. yPinX1 inhibits telomerase activity by sequestering yTERT (telomerase reverse transcriptase) from uniting with yTR (telomerase template RNA) in the nucleolus of yeast cells. However, the mechanism underlying the action of hPinX1 on telomerase regulation in human cells is not known. We here demonstrated that hPinX1 actually has an effect on mediating hTERT nucleolar localization and this effect is mediated by a novel domain enclosed within the central section of the polypeptide. Interestingly, we showed that a reported cancerous mutant form of hPinX1, in which residues of Ser254 and Cys265 are, respectively, mutated to Cys and Tyr, lost the activity on mediating hTERT nucleolar localization. Finally, we provided evidence that mediation of hTERT nucleolar localization and telomerase enzymatic inhibition are two separated function of hPinX1 on telomerase regulation in human cells.