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Universidade Estadual de Campinas (2013)

Lignificação em eucaliptos submetidos aos estresses de frio e seca : aspectos bioquímicos e moleculares

Jullyana Cristina Magalhães Silva Moura Sobczak

Titre : Lignificação em eucaliptos submetidos aos estresses de frio e seca : aspectos bioquímicos e moleculares

Lignification in Eucalyptus subjected to cold and drought stresses : biochemical and molecular aspects

Auteur : Jullyana Cristina Magalhães Silva Moura Sobczak

Université de soutenance : Universidade Estadual de Campinas

Grade : Doutora em Biologia Vegetal 2013

Résumé
Lignin is a complex plant phenolic compound whose properties allow it to perform its functions, which are mainly the mechanical support of plant tissues and efficient xylem sap conduction. Currently, lignin is intensively studied because its hydrophobic feature and high resistance to chemical and enzymatic degradation makes it undesirable for the production of paper and biofuels. Thus, several studies are being conducted with the goal of understanding the biosynthesis of lignin in order to reduce the content or change the reactivity of lignin in plants used in these processes. In this work, it was studied the lignification in Eucalyptus species used for paper production. Low temperature and water stress treatments were used as modulators of lignification. Biochemical analysis of lignin and gene expression studies were performed in two distinct regions of the stem (stem tips and bases) for plants exposed to stress and control plants. After this, the observed biochemical changes (preferentially those which could be beneficial to paper production) were related to results of gene expression. It was observed that in urograndis P42 hybrids (Eucalyptus urophylla S. T. Blake x Eucalyptus grandis Hill ex-Maiden), the reduction of the expression of LACA8, CAD2 and 4CL0 and the increased expression of POX8.1 and CCR1 may be related to the beneficial biochemical responses observed, that is, an increased coniferaldehyde, soluble lignin and cellulose digestibility. In Eucalyptus globulus Labill, analysis of plants submitted to drought treatments indicated that a reduced expression of LACA0 and CCR1, and an increased expression of POX4 and HCT1, may be related to increased digestibility of cellulose. Besides that, a reduced expression of LACA1, LACA6 and DIRI0 may be related to the reduction in total lignin and coniferaldehyde. Additionally, in E. globulus, analysis of plants exposed to cold indicated that the reduction of the expression in CAD1 may be related to the increase in soluble lignin. Finally, in uroglobulus hybrids (E. urophylla S. T. Blake x E. grandis Hill ex-Maiden) x (E. globulus), comparisons of stem bases of plants subjected to drought treatments indicated that reduced expression of DIRI0 may be associated with increased soluble lignin. In this way, this work indicates some genes possibly related to changes in lignin that could be beneficial for production of paper and possibly be desirable for the production of biofuels, although this latter case was not the focus of the work.

Mots clés : Eucalipto , Papel , Lignina , Frio , Seca , Eucalyptus , Paper , Lignin , Cold , Drought

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Page publiée le 26 janvier 2015, mise à jour le 5 juillet 2017