title: Characterization of sugarcane (Saccharum spp.) leaf senescence: implications for biofuel production.
abstract: BACKGROUND
  Second-generation ethanol (2G-bioethanol) uses lignocellulosic feedstocks for ethanol production. Sugarcane is one among the most suitable crops for biofuel production. Its juice is extracted for sugar production, while sugarcane bagasse, straw, and senescing leaves are considered industrial waste. Senescence is the age-dependent deterioration of plant cells, ultimately leading to cell death and completion of the plant life cycle. Because senescing leaves may also be used for biofuel production, understanding the process of natural senescence, including remobilization of nutrients and its effect on cell walls can provide useful information for 2G-bioethanol production from sugarcane leaves.
  
  
  RESULTS
  The natural senescence process in leaves of the commercial sugarcane cultivar RB867515 was investigated. Senescence was characterized by strong reduction in photosynthetic pigments content, remobilization of the nutrients N, P, K, B, Cu, Fe, and Zn, and accumulation of Ca, S, Mg, B, Mn, and Al. No significant changes in the cell-wall composition occurred, and only small changes in the expression of cell wall-related genes were observed, suggesting that cell walls are preserved during senescence. Senescence-marker genes, such as SAG12-like and XET-like genes, were also identified in sugarcane and found to be highly expressed.
  
  
  CONCLUSIONS
  Our study on nutrient remobilization under senescence in a vigorous sugarcane cultivar can contribute to the understanding on how nutrient balance in a high-yielding crop is achieved. In general, neutral monosaccharide profile did not change significantly with leaf senescence, suggesting that senescing leaves of sugarcane can be as a feedstock for biofuel production using pretreatments established for non-senescing leaves without additional efforts. Based on our findings, the potential biotechnological applications for the improvement of sugarcane cultivars are discussed.
authors.affiliation: Genetics and Biotechnology Laboratory, Embrapa Agroenergy (CNPAE), Brasília, DF 70770-901 Brazil.|Genomic Sciences and Biotechnology Program, Universidade Catolica de Brasilia, Brasília, DF 70790‑160 Brazil.
authors.forename: Maria Thereza Bazzo
authors.initials: MTB
authors.lastname: Martins
authors.affiliation: Genetics and Biotechnology Laboratory, Embrapa Agroenergy (CNPAE), Brasília, DF 70770-901 Brazil.
authors.forename: Wagner Rodrigo
authors.initials: WR
authors.lastname: de Souza
authors.affiliation: Genetics and Biotechnology Laboratory, Embrapa Agroenergy (CNPAE), Brasília, DF 70770-901 Brazil.
authors.forename: Bárbara Andrade Dias Brito
authors.initials: BADB
authors.lastname: da Cunha
authors.affiliation: Genetics and Biotechnology Laboratory, Embrapa Agroenergy (CNPAE), Brasília, DF 70770-901 Brazil.
authors.forename: Marcos Fernando
authors.initials: MF
authors.lastname: Basso
authors.affiliation: Genetics and Biotechnology Laboratory, Embrapa Agroenergy (CNPAE), Brasília, DF 70770-901 Brazil.
authors.forename: Nelson Geraldo
authors.initials: NG
authors.lastname: de Oliveira
authors.affiliation: Genetics and Biotechnology Laboratory, Embrapa Agroenergy (CNPAE), Brasília, DF 70770-901 Brazil.
authors.forename: Felipe
authors.initials: F
authors.lastname: Vinecky
authors.affiliation: Genetics and Biotechnology Laboratory, Embrapa Agroenergy (CNPAE), Brasília, DF 70770-901 Brazil.
authors.forename: Polyana Kelly
authors.initials: PK
authors.lastname: Martins
authors.affiliation: Biomass and Biofuel Chemistry Laboratory, Embrapa Agroenergy (CNPAE), Brasília, DF 70770-901 Brazil.
authors.forename: Patrícia Abrão
authors.initials: PA
authors.lastname: de Oliveira
authors.affiliation: Laboratory of Plant Physiological Ecology (LAFIECO), Department of Botany-Institute of Biosciences, University of São Paulo, São Paulo, SP 05508-090 Brazil.
authors.forename: Bruna Cersózimo
authors.initials: BC
authors.lastname: Arenque-Musa
authors.affiliation: Laboratory of Plant Physiological Ecology (LAFIECO), Department of Botany-Institute of Biosciences, University of São Paulo, São Paulo, SP 05508-090 Brazil.
authors.forename: Amanda Pereira
authors.initials: AP
authors.lastname: de Souza
authors.affiliation: Laboratory of Plant Physiological Ecology (LAFIECO), Department of Botany-Institute of Biosciences, University of São Paulo, São Paulo, SP 05508-090 Brazil.
authors.forename: Marcos Silveira
authors.initials: MS
authors.lastname: Buckeridge
authors.affiliation: Genetics and Biotechnology Laboratory, Embrapa Agroenergy (CNPAE), Brasília, DF 70770-901 Brazil.
authors.forename: Adilson Kenji
authors.initials: AK
authors.lastname: Kobayashi
authors.affiliation: Genetics and Biotechnology Laboratory, Embrapa Agroenergy (CNPAE), Brasília, DF 70770-901 Brazil.|Genomic Sciences and Biotechnology Program, Universidade Catolica de Brasilia, Brasília, DF 70790‑160 Brazil.
authors.forename: Betania Ferraz
authors.initials: BF
authors.lastname: Quirino
authors.affiliation: Genetics and Biotechnology Laboratory, Embrapa Agroenergy (CNPAE), Brasília, DF 70770-901 Brazil.
authors.forename: Hugo Bruno Correa
authors.initials: HBC
authors.lastname: Molinari
keywords: Biotechnology; Cell wall; Lignocellulosic ethanol; Natural leaf senescence; Nutrient remobilization; Renewable energy; Sugarcane