Expression of lignith biosynthesis pathway genes in stems of Eucalyptus globulus ans E. urograndis exposed to different temperatures

Author(s)

Vanessa Regina Tofanello

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2015-07-28

Examining board members

Paulo Mazzafera; Sara Adrián López de Andrade; Márcio José da Silva

• Advisor: Paulo Mazzafera

Abstract

It is known that perennial plant species must endure periodic alterations in the environment and frequently find themselves in the need of mechanisms necessary for survival in such inconstant conditions, by means of anatomical, cellular and molecular alterations. Stresses induced by extremes temperature are one of the main limiting factors for geographical distribution and seasonal growth in various groups for plants, affecting quality and productivity in several crops and forests. Cellulose and lignin are the main polymers found in plants. Lignin plays an important role in the plant, supporting cellulose microfibrils in the cell walls, however, when it comes to industrial processes, lignin is an obstacle making it difficult to extract cellulose compounds of economic importance, as observed of eucalyptus plants. Genes acting in the lignin biosynthesis pathway were selected form an RNAseq database. These genes were compared with those from E. grandis genome and two genes were identified for codification of phenylalanine ammonia-lyase (EgrPAL2 and EgrPAL3), one for cinnamic acid 4-hydroxylase (EgrC4H2), one for hydroxycinnamoyl-CoA: shikimate/quinate hydroxycinnmoyl transferase (EgrHCT), one for caffeoyl-CoA O-methyltransferase (EgrCCoAOMT-like17) and one for Ferulate 5-hydroxylase (EgrF5H1). Sequences were identified using sequence alignment and phylogenetic trees. E. globulus and E. urograndis plants ¿ the same species used in the RNAseq database ¿ with 4 to 5 months of age were kept for 22 days in temperatures of 5oC, 10oC, 15oC, 20oC, 25oC, 30oC and 35oC. Analysis of growth was performed for stems, and leaves were analyzed for photosynthesis, fluorescence and pigment content. Total lignin, soluble lignin oligomers and S/G ratio was analyzed in the stems. In a general way, the lowest temperatures limited growth and reduced chlorophyll content, but anthocyanins were increased. The effect of cold was more important than that of higher temperatures for the same species, although E. globulus was apparently less affected E. urograndis, mainly for stem growth, photosynthesis and chlorophyll fluorescence. Lignin content showed little variation in E. urograndis and was smaller for lower temperatures in E. globulus, increasing with intermediate temperatures and decreasing in the highest ones. E. globulus showed the lowest average lignin content and highest S/G ratio. There were no significant alterations in oligomers or S/G ratio in either species regarding different temperatures. Gene expression data were well correlated with variation in lignin content for E. globulus, with the highest expression peak between 10oC e 15oC. The results demonstrate that lignin content was altered in E. globulus mainly for the effect on overall lignin metabolism, without any qualitative effect, considering S/G ratio, which would implicate in alteration in the expression of specific enzymes. Furthermore, data shows there can be variation related to genes responding to temperature treatments, considering the genes analyzed here and identified in the genome of E. grandis as active in the biosynthesis of lignin did not necessarily behave as expected, as was the case for EgrPAL2 and EgrPAL3, and EgrCCoAMT-like17. This opens new perspectives for functional studies with different genes and "gene-like" identified in E. grandis genome for different species of eucalyptus (AU)

• FAPESP's process: 12/22886-8 - Transcriptome of Eucalyptus globulus and E. urograndis in response to low temperature: lignin
• Grantee: Vanessa Regina Tofanello
• Support Opportunities: Scholarships in Brazil - Master