Influence of laccases and microRNAs on the lignification of Eucalyptus

Author(s)

Felipe Thadeu Tolentino

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2020-10-20

Examining board members

Paulo Mazzafera; Renato Vicentini; Michael dos Santos Brito; José Sérgio de Macedo Soares; Paula Macedo Nobile

• Advisor: Paulo Mazzafera

Abstract

Lignin is a complex phenolic biopolymer formed by randomly organized monolignols and, next to cellulose, is one the main components of plant cell walls. Lignin greatly affects the pulping process during cellulose paste and paper production. Monolignols are produced by enzymes from the phenypropanoid pathway and these compounds are exported out of the cell, to the cell wall, where laccases and peroxidases perform their oxidation, causing their polymerization. Herein we characterized a laccase gene from eucalypt, EglLAC48, which is phylogenetically close to AtLAC15 from Arabidopsis, and is strongly associated with lignification. Overexpression of EglLAC48 demonstrate a phenotypic recovery in lac17 mutants of Arabidopsis that are lignin-deficient, and its mRNA localization shows that EglLAC48 is expressed in the developing xylem of Eucalyptus seedlings. The comprehension of how the pathways that lead to lignification are regulated could bring important tools to produce plants with commercial interest. The miRNAs have also proven to be important genetic regulators in plants. We also identified and characterized an expression profile for miRNAs and genes related to lignification processes using a reaction wood model. E. globulus and E. grandis showed distinct global miRNA expression profiles. Among the miRNAs identified, miRNAs from the miR families miR166, miR482, miR168, miR319 and, additionally, four nonconserved miRNAs (euc-mir-novel2-3p, euc-mir-novel1-5p, euc-mir-novel6-3p and euc-mir-novel3-3p) were the most expressed ones. A Gene Ontology analysis showed enrichment for several cellular processes including DNA binding and copper ion binding, which has a stronger relationship with lignification processes. The group of laccases greatly includes predicted targets for miR397, however, some of the predicted targets could not be confirmed when tested for mRNA cleavage. Therefore, EglLAC48 presents itself as an important laccase in the process of lignification during the initial development of xylem and E. globulus and E. grandis showed distinct expression profiles for miRNAs and possible candidates that may target processes of lignification appeared during our analyses (AU)

• FAPESP's process: 14/23230-4 - Influence of microRNAs in lignification pathways of Eucalyptus grandis and E. globulus
• Grantee: Felipe Thadeu Tolentino
• Support Opportunities: Scholarships in Brazil - Doctorate