RESUMO
ABSTRACT Saccharum spontaneum has been used for the development of energy cane a crop aimed to be used for the production of second-generation ethanol, or lignocellulosic ethanol. Lignin is a main challenge in the conversion of cell wall sugars into ethanol. In our studies to isolate the genes the lignin biosynthesis in S. spontaneum we have had great difficulty in RT-PCR reactions. Thus, we evaluated the effectiveness of different additives in the amplification of these genes. While COMT and CCoAOMT genes did not need any additives for other genes there was no amplification (HCT, F5H, 4CL and CCR) or the yield was very low (CAD and C4H). The application of supplementary cDNA was enough to overcome the non-specificity and low yield for C4H and C3H, while the addition of 0.04% BSA + 2% formamide was effective to amplify 4CL, CCR, F5H and CCR. HCT was amplified only by addition of 0.04% BSA + 2% formamide + 0.1 M trehalose and amplification of PAL was possible with addition of 2% of DMSO. Besides optimization of expression assays, the results show that additives can act independently or synergistically.
Assuntos
Regulação da Expressão Gênica de Plantas/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa/métodos , Técnicas de Amplificação de Ácido Nucleico/métodos , Saccharum/genética , Parede Celular/genética , Primers do DNA , Etanol , Lignina/biossíntese , Lignina/genética , Metiltransferases/genéticaRESUMO
Eucalyptus ESTs libraries were screened for genes involved in lignin biosynthesis. This search was performed under the perspective of recent revisions on the monolignols biosynthetic pathway. Eucalyptus orthologues of all genes of the phenylpropanoid pathway leading to lignin biosynthesis reported in other plant species were identified. A library made with mRNAs extracted from wood was enriched for genes involved in lignin biosynthesis and allowed to infer the isoforms of each gene family that play a major role in wood lignin formation. Analysis of the wood library suggests that, besides the enzymes of the phenylpropanoids pathway, chitinases, laccases, and dirigent proteins are also important for lignification. Colocalization of several enzymes on the endoplasmic reticulum membrane, as predicted by amino acid sequence analysis, supports the existence of metabolic channeling in the phenylpropanoid pathway. This study establishes a framework for future investigations on gene expression level, protein expression and enzymatic assays, sequence polymorphisms, and genetic engineering
Assuntos
Etiquetas de Sequências Expressas , Eucalyptus/genética , Lignina/biossíntese , FenilpropionatosRESUMO
The present review focuses on some aspects of enzymology and on the ligninase mechanism in particular, with a survey of genetic studies carried out during the last few years. Some white-rot fungi are currently known to the most efficient lignin degrading organisms. Among them, Chrysonilia sitophila is emphasized for its high ligninolytic activity. Ligninases are enzymes which need H2O2 for activity and have intrinsic peroxidase activity. A free radical mechanism for ligninase-catalyzed degradation in suggested