Brassinosteroids （BRs） are a class of steroid hormones that are essential for plant growth and development. The BR signal transduction pathway in the dicot model plantArabidopsis is well established, but the compone...Brassinosteroids （BRs） are a class of steroid hormones that are essential for plant growth and development. The BR signal transduction pathway in the dicot model plantArabidopsis is well established, but the components connecting the BR signaling steps in rice have not been fully explored. For example, how the BR signaling is fine-tuned in rice, especially at the BR receptor level, is largely unknown. Here we show that OsPRA2, a rice small G protein, plays a repressive role in the BR signaling pathway. Lamina inclination, coleoptile elongation, and root inhibition assays indicated that rice plants with suppressed expression of OsPRA2 were more sensitive to exogenously applied brassinolide than the wild-type plants. Conversety, rice overexpressing OsPRA2 was less sensitive to exogenous brassinolide. Further study uncovered that OsPRA2 inhibited the dephosphorylation of, and thus inactivated the transcription factor BRASSINAZOLE- RESISTANT 1 （OsBZR1）. More importantly, OsPRA2 was found to co-localize with and directly bind to rice BR receptor BRASSlNOSTEROID-INSENSITIVE 1 （OsBRI1） at the plasma membrane. Additionally, the in vitro assays showed that OsPRA2 inhibits its autophosphorylation. This OsPRA2-OsBRI1 interaction led to the dissociation of OsBRI1 from its co-receptor OsBAK1, and abolished OsBRIl-mediated phosphorylation of OsBAK1. Together, these results reveal a possible working mechanism of OsPRA2 as a novel negative regu- lator on OsBRI1 and OsBZR1 and extend the knowledge about the regulatory mechanism of rice BR signaling.展开更多
The small GTPases of Rop/Rho family is central regulators of important cellular processes in plants. Tobacco small G protein gene NtRop1 has been isolated; however, its roles in stress responses were unknown. In the p...The small GTPases of Rop/Rho family is central regulators of important cellular processes in plants. Tobacco small G protein gene NtRop1 has been isolated; however, its roles in stress responses were unknown. In the present study, the genomic sequence of NtRop1 was cloned, which has seven exons and six introns, similar to the Rop gene structure from Arabidopsis. The NtRop1 gene was constitutively expressed in the different organs whereas the other six Rop genes from tobacco had differential expression patterns. The expression of the NtRop1 gene was moderately induced by methyl viologen, NaCl, and ACC treatments, but slightly inhibited by ABA treatment, with no significant induction by NAA treatment. The transgenic Arabidopsis plants overexpressing the NtRop1 showed increased salt sensitivity as can be seen from the reduced root growth and elevated relative electrolyte leakage. The hydrogen peroxide production was also promoted in the NtRop1-trangenic plants in comparison with wild type plants. These results imply that the NtRop1 may confer salt sensitivity through activation of H2O2 production during plant response to salt stress.展开更多
Non-small-cell lung carcinoma （NSCLC） is one of the most frequently diagnosed malignancies worldwide. Previous studies have shown that microRNA-449b （miR-449b） functions as a tumor suppressor in many cancers. Howe...Non-small-cell lung carcinoma （NSCLC） is one of the most frequently diagnosed malignancies worldwide. Previous studies have shown that microRNA-449b （miR-449b） functions as a tumor suppressor in many cancers. However, the role of miR- 449b in NSCLC is still unknown. In the present study, miR-449b was significantly down- regulated in NSCLC samples and cell lines. Bioinformatics analysis revealed that 3＇-UTR region of leucine rich repeat containing G protein-coupled receptor 4 （LGR4） mRNA had putative complementary sequences to miR-449b, which was further confirmed by the luciferase assay. Western blotting showed that restoration of miR-449b in NSCLC cells decreased the expression of LGR4. Interestingly, over-expression of miR-449b inhibited growth and invasion of NSCLC cells in vitro. Furthermore, ectopic expression of LGR4 reversed miR-449b-suppressed proliferation and invasion of NSCLC cells. Therefore, the data of the present study demonstrate that miR-449b inhibits tumor cell growth and invasion by targeting LGR4 in NSCLC.展开更多
文摘Brassinosteroids （BRs） are a class of steroid hormones that are essential for plant growth and development. The BR signal transduction pathway in the dicot model plantArabidopsis is well established, but the components connecting the BR signaling steps in rice have not been fully explored. For example, how the BR signaling is fine-tuned in rice, especially at the BR receptor level, is largely unknown. Here we show that OsPRA2, a rice small G protein, plays a repressive role in the BR signaling pathway. Lamina inclination, coleoptile elongation, and root inhibition assays indicated that rice plants with suppressed expression of OsPRA2 were more sensitive to exogenously applied brassinolide than the wild-type plants. Conversety, rice overexpressing OsPRA2 was less sensitive to exogenous brassinolide. Further study uncovered that OsPRA2 inhibited the dephosphorylation of, and thus inactivated the transcription factor BRASSINAZOLE- RESISTANT 1 （OsBZR1）. More importantly, OsPRA2 was found to co-localize with and directly bind to rice BR receptor BRASSlNOSTEROID-INSENSITIVE 1 （OsBRI1） at the plasma membrane. Additionally, the in vitro assays showed that OsPRA2 inhibits its autophosphorylation. This OsPRA2-OsBRI1 interaction led to the dissociation of OsBRI1 from its co-receptor OsBAK1, and abolished OsBRIl-mediated phosphorylation of OsBAK1. Together, these results reveal a possible working mechanism of OsPRA2 as a novel negative regu- lator on OsBRI1 and OsBZR1 and extend the knowledge about the regulatory mechanism of rice BR signaling.
基金the National Basic Research Program of China (Grant No. 2006CB100102)the High-Tech Program (863 Program) of China (Grant No. 2006AA10Z18201)
文摘The small GTPases of Rop/Rho family is central regulators of important cellular processes in plants. Tobacco small G protein gene NtRop1 has been isolated; however, its roles in stress responses were unknown. In the present study, the genomic sequence of NtRop1 was cloned, which has seven exons and six introns, similar to the Rop gene structure from Arabidopsis. The NtRop1 gene was constitutively expressed in the different organs whereas the other six Rop genes from tobacco had differential expression patterns. The expression of the NtRop1 gene was moderately induced by methyl viologen, NaCl, and ACC treatments, but slightly inhibited by ABA treatment, with no significant induction by NAA treatment. The transgenic Arabidopsis plants overexpressing the NtRop1 showed increased salt sensitivity as can be seen from the reduced root growth and elevated relative electrolyte leakage. The hydrogen peroxide production was also promoted in the NtRop1-trangenic plants in comparison with wild type plants. These results imply that the NtRop1 may confer salt sensitivity through activation of H2O2 production during plant response to salt stress.
文摘Non-small-cell lung carcinoma （NSCLC） is one of the most frequently diagnosed malignancies worldwide. Previous studies have shown that microRNA-449b （miR-449b） functions as a tumor suppressor in many cancers. However, the role of miR- 449b in NSCLC is still unknown. In the present study, miR-449b was significantly down- regulated in NSCLC samples and cell lines. Bioinformatics analysis revealed that 3＇-UTR region of leucine rich repeat containing G protein-coupled receptor 4 （LGR4） mRNA had putative complementary sequences to miR-449b, which was further confirmed by the luciferase assay. Western blotting showed that restoration of miR-449b in NSCLC cells decreased the expression of LGR4. Interestingly, over-expression of miR-449b inhibited growth and invasion of NSCLC cells in vitro. Furthermore, ectopic expression of LGR4 reversed miR-449b-suppressed proliferation and invasion of NSCLC cells. Therefore, the data of the present study demonstrate that miR-449b inhibits tumor cell growth and invasion by targeting LGR4 in NSCLC.
