RESUMO
Lateral roots (LRs) are a major determinant of the root system architecture in plants, and developmental plasticity of LR formation is critical for the survival of plants in changing environmental conditions. In Arabidopsis thaliana, genetic pathways have been identified that regulate LR branching in response to numerous environmental cues, including some nutrients, salt, and gravity. However, it is not known how genetic components are involved in the LR adaptation response to cold. Here, we demonstrate that CYTOKININ RESPONSE FACTOR2 (CRF2) and CRF3, encoding APETALA2 transcription factors, play an important role in regulating Arabidopsis LR initiation under cold stress. Analysis of LR developmental kinetics demonstrated that both CRF2 and CRF3 regulate LR initiation. crf2 and crf3 single mutants exhibited decreased LR initiation under cold stress compared with the wild type, and the crf2 crf3 double mutants showed additively decreased LR densities compared with the single mutants. Conversely, CRF2 or CRF3 overexpression caused increased LR densities. CRF2 was induced by cold via a subset of the cytokinin two-component signaling (TCS) pathway, whereas CRF3 was upregulated by cold via TCS-independent pathways. Our results suggest that CRF2 and CRF3 respond to cold via TCS-dependent and TCS-independent pathways and control LR initiation and development, contributing to LR adaptation to cold stress.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Temperatura Baixa , Raízes de Plantas/metabolismo , Fatores de Transcrição/metabolismo , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Proteínas de Arabidopsis/genética , Regulação da Expressão Gênica de Plantas/genética , Regulação da Expressão Gênica de Plantas/fisiologia , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Transdução de Sinais/genética , Transdução de Sinais/fisiologia , Fatores de Transcrição/genéticaRESUMO
The clinical efficacy of the monotherapy involving the administration of a high dose of dihydroartemisinin (DHA 900 mg) for 5 days was compared with that of the combination regimen (DHA 600 mg + mefloquine [MQ] 750 mg) in an open randomized study in 90 patients with uncomplicated falciparum malaria in the southern part of Viet Nam. Patients were randomly treated with the DHA-5 day monotherapy regimen (300, 300, 100, 100, and 100 mg given at 0, 24, 48, 72, and 96 h) or the DHA-MQ combination regimen (300 mg DHA at 0 h, then 300 mg DHA plus 750 mg MQ at 24 h). The end points for comparison were the parasite and fever clearance times (PCT and FCT) and recrudescence rates (by day 28 for DHA-5 days and day 42 for DHA-MQ). Eighty-nine patients completed the trial per protocol, including 45 cases receiving DHA-5 day and 44 receiving DHA-MQ. There was no difference in clinical manifestations, parasitemia density or other laboratory tests between the two patient groups. The PCTs were 35.3 +/- 17.4 h (mean +/- SD; range, 12-96) and 37.8 +/- 19.2 h (range, 12-96), respectively for the DHA-5 day and DHA-MQ regimens (P > 0.05). Twelve patients receiving the DHA-5 day regimen relapsed with falciparum malaria by day 28 (26.7%) and 5 patients receiving the DHA-MQ regimen relapsed by day 42 (11.4%) (P=0.07). Survival analysis showed that the DHA-5 day regimen had a radical cure rate significantly lower than that of the DHA-MQ regimen (P=0.003). The high dose of DHA in the monotherapy regimen did not increase the efficacy of the treatment of patients with uncomplicated Plasmodium falciparum malaria. The DHA combination regimens are suggested to be the better regimens for DHA.
