RESUMO
Heterotrimeric GTP-binding protein (G-protein)-mediated abscisic acid (ABA) and drought-stress responses have been documented in numerous plant species. However, our understanding of the function of rice G-protein subunits in ABA signalling and drought tolerance is limited. In this study, the function of G-protein subunits in ABA response and drought resistance in rice plants was explored. It was found that the transcription level of qPE9-1 (rice Gγ subunit) gradually decreased with increasing ABA concentration and the lack of qPE9-1 showed an enhanced drought tolerance in rice plants. In contrast, mRNA levels of RGB1 (rice Gß subunit) were significantly upregulated by ABA treatment and the lack of RGB1 led to reduced drought tolerance. Furthermore, the results suggested that qPE9-1 negatively regulates the ABA response by suppressing the expression of key transcription factors involved in ABA and stress responses, while RGB1 positively regulates ABA biosynthesis by upregulating NCED gene expression under both normal and drought stress conditions. Taken together, it is proposed that RGB1 is a positive regulator of the ABA response and drought adaption in rice plants, whereas qPE9-1 is modulated by RGB1 and functions as a negative regulator in the ABA-dependent drought-stress responses.
Assuntos
Ácido Abscísico/metabolismo , Aclimatação , Proteínas de Ligação ao GTP/genética , Regulação da Expressão Gênica de Plantas , Oryza/genética , Proteínas de Plantas/genética , Secas , Proteínas de Ligação ao GTP/metabolismo , Oryza/metabolismo , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Transdução de SinaisRESUMO
AtNUDT5 is a cytosol Nudix that catalyzes the hydrolysis of a variety of substrates. In this report, a 1,387-bp 5'-flanking region of the AtNUDT5 gene was isolated from Arabidopsis thaliana. The tissue-specific activity of the 5'-flanking region was investigated by using the GUS gene as a reporter in transgenic A. thaliana plants. Weak GUS activity appeared in vascular tissues of young plants, strong GUS activity appeared in the axial roots, but no GUS activity was observed in the root cap, lateral roots, rosette leaf, mature silique and reproductive tissues such as stamen, pistil, and petal. Furthermore, by using these transgenic A. thaliana plants, results of the histochemical staining and fluorometric assays of GUS activity showed that the AtNUDT5 promoter can be activated by both avirulent Pst avrRpm1 and virulent Pst strains at 5 h post-infiltration and that the activity of AtNUDT5 promoter increased significantly at 24 h post-infiltration. Taken together, our results demonstrated that the AtNUDT5 promoter is pathogen-responsive. The promoter may be used to develop transgenic plants with an increased tolerance to pathogenic stresses.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Proteínas de Bactérias/genética , Regulação da Expressão Gênica de Plantas , Raízes de Plantas/genética , Pseudomonas syringae/genética , Pirofosfatases/genética , Região 5'-Flanqueadora , Arabidopsis/metabolismo , Arabidopsis/microbiologia , Proteínas de Arabidopsis/metabolismo , Proteínas de Bactérias/metabolismo , Sequência de Bases , Flores/genética , Flores/metabolismo , Flores/microbiologia , Interações Hospedeiro-Patógeno , Dados de Sequência Molecular , Folhas de Planta/genética , Folhas de Planta/metabolismo , Folhas de Planta/microbiologia , Raízes de Plantas/metabolismo , Raízes de Plantas/microbiologia , Caules de Planta/genética , Caules de Planta/metabolismo , Caules de Planta/microbiologia , Plantas Geneticamente Modificadas , Regiões Promotoras Genéticas , Pseudomonas syringae/metabolismo , Pirofosfatases/metabolismo , Nudix HidrolasesRESUMO
Proanthocyanidins (PAs) as the end products of flavonoid biosynthetic pathway mainly accumulate in seed coat but their biological function is largely unknown. We studied the anti-oxidation ability in seed coat and germination changes under externally applied oxidative stresses in PAs-deficient mutants of Arabidopsis. Germination of PAs-deficient mutant seeds was faster than that of wild-type under low or no oxidative stress, suggesting a PAs-induced inhibition of germination. When the applied oxidative stress was high, germination of PAs-deficient mutants was lower than that of wild-type, suggesting a loss of PAs-related anti-oxidation ability in the mutants. Using ABA signaling mutants, our studies demonstrated that both ABA signaling pathway and PAs were important for the response to serve oxidative stress during seed germination. However, the discrepancy of the response between abi mutants and PAs mutants to oxidative stress suggests that ABA signaling pathway may not play a major role in PAs' action in alleviating oxidative stress. Under low or no oxidative stress, germination was mainly determined by the ABA content in seed and the PAs-deficient mutant seeds germinated faster due to their lower ABA content than wild-type. However, oxidative injury inhibited germination when PAs-deficient seeds germinated under high oxidative stress. Wild-type exhibited higher germination under the high oxidative stress due to the PAs' anti-oxidation ability. Oxidative stress applied externally led to changes in endogenous PAs contents that coincided with the expression changes of PAs biogenesis genes. PAs modulated the activities of some key enzymes that controlled the levels of reactive oxygen species and the anti-oxidation capacity during the seed germination. This work suggests that PAs contribute to the adaptive mechanism that helps germination under environmental stresses by playing dual roles in both germination control and anti-oxidation reaction.