Caracterização molecular do fator de transcrição shine e seu potencial como regulador master na síntese de parede celular secundária em Sorghum bicolor L.
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Data
2017-06-05
Autores
Takahashi, Natália Gonçalves [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A busca pela diversificação de fontes da matriz energética, priorizando fontes renováveis, acarreta no maior consumo de etanol de primeira geração, podendo este ser insuficiente em suprir a necessidade da frota brasileira. Dessa forma, o etanol de segunda geração (E2G) surge como uma alternativa para aumento da produção de combustíveis renováveis. Ele é produzido a partir da fermentação dos resíduos de glicose após a quebra da celulose presente na biomassa vegetal. Contudo, além da celulose, a biomassa vegetal é também composta pela lignina, composto considerado recalcitrante no processo de obtenção deste tipo de etanol. Para transpor este obstáculo, é necessário encontrar maneiras de diminuir a quantidade ou modificar a composição da lignina. Fatores de transcrição (FTs) são alvos altamente promissores para a modificação deste polímero, uma vez que estão envolvidos com a regulação de sua via de biossíntese, bem como, da formação de toda parede celular secundária (PCS). Plantas de arroz transformadas para a superexpressão de AtSHN2 de Arabdopsis, apresentaram uma diminuição na quantidade de lignina e mostraram uma modulação na via de celulose, enquanto que a superexpressão do outro gene SHN de Arabidopsis (AtSHN1) em Arabidopsis apresentou uma modificação na via de biossíntese de cera e cutina. Isto ressalta a necessidade de avaliar os FTs de maneira espécie-específica. Assim sendo, este trabalho vem com o objetivo de ajudar a elucidar os mecanismos de funcionamento do FT SHINE (SHN), considerado um potencial regulador da PCS em gramíneas. Para a caracterização do FT SbSHN em sorgo foi primeiramente realizado um alinhamento de sequências de aminoácidos, contendo as proteínas codificadas pelos dois genes SHN em sorgo (SbSHN1 – Sb04g006970 e SbSHN2 – Sb10g023600) com outras sequências SHN disponíveis na literatura. Em seguida foi gerada uma árvore filogenética contendo todos esses mesmos SHN. Após isso, foi realizada a clonagem do FT SbSHN1 em vetor comercial pENTR/D-TOPO (Invitrogen), após verificação, a sequência foi recombinada com vetores de destino. Primeiramente, com o vetor pDEST15 para a expressão heteróloga da proteína SHN em E. coli.. De maneira complementar foi produzido um peptídeo sintético para reconhecimento da proteína SbSHN (anticorpo antiSHN). Posteriormente foi produzido um vetor contendo a sequencia de SHN em fusão com GFP, que foi utilizado para agroinfiltração de folhas de N. benthamiana, a fim de observar a localização subcelular do FT SbSHN. Para determinação da expressão através de qPCR em sorgo foram utilizados a folha, dividida em base e ponta, e a inflorescência, imatura e madura. Além disso, foi realizada a imunoprecipitação de cromatina (ChIP) das inflorescências imaturas e maduras de sorgo, com posterior análise inicial por ChIPqPCR para validação de alguns alvos de SbSHN. Como resultados, através da expressão heteróloga foi produzida uma proteína com massa de aproximadamente 52kDa (massa da proteína SHN adicionada de cauda GST), que foi reconhecida pelo anticorpo antSHN produzido. Foi confirmada a presença do FT SbSHN no núcleo celular, através de observação das folhas transformadas por agroinfiltração. As inflorescências imaturas de sorgo apresentaram maior expressão tanto de SbSHN1 quanto de SbSHN2. Com a técnica de ChIPqPCR foi possível validar in vivo os alvos SbNAC91 (Sb07g001550), SbNAC115 (Sb10g000460), SbMYB87 (Sb07g024970) e SbMYB60 (Sb04g031110) do FT SbSHN em sorgo. Em uma perspectiva de longo prazo, acredita-se que o conhecimento obtido a partir destes estudos não só fornecerão informações importantes sobre a função dos reguladores SHN em todo o reino vegetal, mas também fornecer uma poderosa ferramenta para a engenharia metabólica de compostos fenólicos e lignina por meio de melhoramento convencional ou abordagens transgênicas, impactando diretamente sobre a produção de E2G.
The search for alternative sources of the energy, prioritizing renewable sources, increase the consumption of first generation ethanol, which could not be enough to supply the needs of the Brazilian flex fuel car fleet. In this scenario, second generation ethanol (E2G) appears as an alternative to increase production of renewable fuels. E2G it is produced from the fermentation of glucose residues after breaking the cellulose present in the plant biomass. However, adhered to the cellulose is lignin, a compound considered recalcitrant in the process of obtaining this type of ethanol. To overcome this obstacle, it is necessary to find ways to decrease the amount or modify the lignin composition. Transcription factors (TFs) are highly promising targets for the modification of this polymer, since they are involved in the regulation of its biosynthesis pathway, as well as the formation of the whole secondary cell wall (PCS). Rice plants transformed for the overexpression of AtSHN2 from Arabidopsis showed a decrease in the amount of lignin and a modulation of cellulose pathway whereas the overexpression of another gene of SHN (AtSHN1) in Arabidopsis showed a modification in the biosynthesis pathway of wax and cutin. This highlights the need to evaluate TFs in a species-specific manner. Basing on this, the present work has the objective of helping to elucidate the mode of action of TF SHINE (SHN), considered a potential regulator of PCS in grasses. Aiming to characterize SbSHN TF in sorghum, initially an alignment was performed using amino acid sequence of proteins encoded by the two SHN genes in sorghum (SbSHN1 - Sb04g006970 and SbSHN2 - Sb10g023600) with other SHN sequences available in the literature. Then a phylogenetic tree containing all these SHN sequences was generated. After that, the SbSHN1 FT was cloned into commercial vector pENTR / D-TOPO (Invitrogen) and later used to recombinate in different destination vectors using gateway system. First, the vector pDEST15 was used for the production of heterologous expression in E. coli. Complementary, a synthetic peptide was produced for recognition of the SbSHN protein (antiSHN antibody). In parallel, the vector pK7WGF2 was used to obtain SHN phusioned to GFP. This vector was transientilly expressed in leaves of N. benthamiana in order to observe the subcellular location of SbSHN TF. Complementary, to determine the expression through qPCR, sorghum leaves, were splitted in base and tip, and the inflorescence, in immature and mature developmental stages, were used. In addition, chromatin immunoprecipitation (ChIP) of immature and mature sorghum inflorescences was performed, with initial analysis by ChIPqPCR for validation of some SbSHN targets. As results, through heterologous expression, a protein with mass of approximately 52kDa (mass of the SHN protein added with GST tail) was obtained, which was recognized by the antiSHN antibody produced. The presence of SbSHN TF in the cell nucleus was confirmed by observation of the transformed leaves by agroleakage. The immature inflorescences of sorghum presented higher expression level of both SbSHN1 and SbSHN2 genes. With the ChIPqPCR technique it was possible to validate in vivo some SHN targets such as: SbNAC91 (Sb07g001550), SbNAC115 (Sb10g000460), SbMYB87 (Sb07g024970) and SbMYB60 (Sb04g031110) in sorghum. In a long-term perspective, we believe that the knowledge gained from these studies will not only provide important information about the function of SHN as a master regulators throughout the plant kingdom, but also provide a powerful tool for the metabolic engineering of phenolic compounds and lignin using conventional breeding or transgenic approaches, directly impacting the production of E2G.
The search for alternative sources of the energy, prioritizing renewable sources, increase the consumption of first generation ethanol, which could not be enough to supply the needs of the Brazilian flex fuel car fleet. In this scenario, second generation ethanol (E2G) appears as an alternative to increase production of renewable fuels. E2G it is produced from the fermentation of glucose residues after breaking the cellulose present in the plant biomass. However, adhered to the cellulose is lignin, a compound considered recalcitrant in the process of obtaining this type of ethanol. To overcome this obstacle, it is necessary to find ways to decrease the amount or modify the lignin composition. Transcription factors (TFs) are highly promising targets for the modification of this polymer, since they are involved in the regulation of its biosynthesis pathway, as well as the formation of the whole secondary cell wall (PCS). Rice plants transformed for the overexpression of AtSHN2 from Arabidopsis showed a decrease in the amount of lignin and a modulation of cellulose pathway whereas the overexpression of another gene of SHN (AtSHN1) in Arabidopsis showed a modification in the biosynthesis pathway of wax and cutin. This highlights the need to evaluate TFs in a species-specific manner. Basing on this, the present work has the objective of helping to elucidate the mode of action of TF SHINE (SHN), considered a potential regulator of PCS in grasses. Aiming to characterize SbSHN TF in sorghum, initially an alignment was performed using amino acid sequence of proteins encoded by the two SHN genes in sorghum (SbSHN1 - Sb04g006970 and SbSHN2 - Sb10g023600) with other SHN sequences available in the literature. Then a phylogenetic tree containing all these SHN sequences was generated. After that, the SbSHN1 FT was cloned into commercial vector pENTR / D-TOPO (Invitrogen) and later used to recombinate in different destination vectors using gateway system. First, the vector pDEST15 was used for the production of heterologous expression in E. coli. Complementary, a synthetic peptide was produced for recognition of the SbSHN protein (antiSHN antibody). In parallel, the vector pK7WGF2 was used to obtain SHN phusioned to GFP. This vector was transientilly expressed in leaves of N. benthamiana in order to observe the subcellular location of SbSHN TF. Complementary, to determine the expression through qPCR, sorghum leaves, were splitted in base and tip, and the inflorescence, in immature and mature developmental stages, were used. In addition, chromatin immunoprecipitation (ChIP) of immature and mature sorghum inflorescences was performed, with initial analysis by ChIPqPCR for validation of some SbSHN targets. As results, through heterologous expression, a protein with mass of approximately 52kDa (mass of the SHN protein added with GST tail) was obtained, which was recognized by the antiSHN antibody produced. The presence of SbSHN TF in the cell nucleus was confirmed by observation of the transformed leaves by agroleakage. The immature inflorescences of sorghum presented higher expression level of both SbSHN1 and SbSHN2 genes. With the ChIPqPCR technique it was possible to validate in vivo some SHN targets such as: SbNAC91 (Sb07g001550), SbNAC115 (Sb10g000460), SbMYB87 (Sb07g024970) and SbMYB60 (Sb04g031110) in sorghum. In a long-term perspective, we believe that the knowledge gained from these studies will not only provide important information about the function of SHN as a master regulators throughout the plant kingdom, but also provide a powerful tool for the metabolic engineering of phenolic compounds and lignin using conventional breeding or transgenic approaches, directly impacting the production of E2G.
Descrição
Palavras-chave
Etanol 2G, Fator de transcrição, SHINE, Sorgo, Parede secundária, 2G Ethanol, Transcription factor, Sorghum, Secondary wall