RESUMO
Maize (Zea mays) is a major staple crop in Africa, where its yield and the livelihood of millions are compromised by the parasitic witchweed Striga. Germination of Striga is induced by strigolactones exuded from maize roots into the rhizosphere. In a maize germplasm collection, we identified two strigolactones, zealactol and zealactonoic acid, which stimulate less Striga germination than the major maize strigolactone, zealactone. We then showed that a single cytochrome P450, ZmCYP706C37, catalyzes a series of oxidative steps in the maize-strigolactone biosynthetic pathway. Reduction in activity of this enzyme and two others involved in the pathway, ZmMAX1b and ZmCLAMT1, can change strigolactone composition and reduce Striga germination and infection. These results offer prospects for breeding Striga-resistant maize.
Assuntos
Lactonas , Striga , Zea mays , Germinação , Lactonas/metabolismo , Melhoramento Vegetal , Striga/crescimento & desenvolvimento , Zea mays/genética , Zea mays/metabolismoRESUMO
Small heat-shock proteins (sHSP) are the most abundant heat stress-induced proteins in plants. In rice, there are at least seven members of class-I sHSP. A 1.6-kb DNA fragment was isolated from the EcoRI-digested rice genomic library probed with the cDNA pTS1 encoding a 16.9-kDa class-I sHSP. This fragment was composed of 365-bp tandem direct repeats (DRs) and 441-bp near perfect long terminal inverted repeats (LTIRs). The DRs contain 123-bp regions with 99% nucleotide identity to the 5' coding region of the Oshsp16.9B gene. Two putative pseudogenes were deduced from the DRs. Using the LTIR as a specific probe, Southern-blotting analysis showed that there was a single copy of this 1.6-kb DNA fragment in the rice genome. By genomic walking, we located this fragment in proximity 5'-upstream of the Oshsp16.9B gene that was mapped on chromosome 1 with other two class-I sHSP genes, Oshsp16.9A and Oshsp16.9C. By comparative analysis of the nucleotide sequences of class-I sHSP genes clustered on chromosome 1 between Tainung No. 67 and Nipponbare cultivars, we confirmed our mapping results of these genes and only the promoter region of Oshsp16.9B was different. However, we found that the expression profile of Oshsp16.9B upon different heat stresses in Nipponbare was not significantly different relative to that in Tainung No. 67.
Assuntos
Cromossomos de Plantas/genética , Genoma de Planta , Proteínas de Choque Térmico/genética , Oryza/genética , Proteínas de Plantas/genética , Sequência de Aminoácidos , Sequência de Bases , Southern Blotting , Mapeamento Cromossômico/métodos , Clonagem Molecular , DNA Complementar , DNA de Plantas/genética , DNA de Plantas/metabolismo , Desoxirribonuclease EcoRI/metabolismo , Regulação da Expressão Gênica de Plantas , Biblioteca Genômica , Proteínas de Choque Térmico/metabolismo , Dados de Sequência Molecular , Proteínas de Plantas/metabolismo , Sequências Repetitivas de Ácido Nucleico , Homologia de Sequência do Ácido NucleicoRESUMO
Objective. To improve a structural pilot model proposed by R. A. Hess, in which element of observation feeling institution was neglected. Method. Real simulation results showed that there was a blind region for small observation signal, and pilot made no response in this region. So we knew that the basic characteristics of the observation feeling institution were observation threshold and observation noise. A Neural Network (NN) receptor model was augmented in the structural pilot model to describe the characteristics of human observation feeling institution. Furthermore, using the augmented model, the affection of the pilot model on the characteristics of the closed-loop system of pilot and controlled element was studied. Result. The affection of NN perception on the closed-loop system was that the stable gain region of the human pilot was extended. Conclusion. The proposed model was reasonable for the element of human feeling institution.
