ShF5H1 overexpression increases syringyl lignin and improves saccharification in sugarcane leaves

ABSTRACT

The agricultural sugarcane residues, bagasse and straws, can be used for second-generation ethanol (2GE) production by the cellulose conversion into glucose (saccharification). However, the lignin content negatively impacts the saccharification process. This polymer is mainly composed of guaiacyl (G), hydroxyphenyl (H), and syringyl (S) units, the latter formed in the ferulate 5-hydroxylase (F5H) branch of the lignin biosynthesis pathway. We have generated transgenic lines overexpressing ShF5H1 under the control of the C4H (cinnamate 4-hydroxylase) rice promoter, which led to a significant increase of up to 160% in the S/G ratio and 63% in the saccharification efficiency in leaves. Nevertheless, the content of lignin was unchanged in this organ. In culms, neither the S/G ratio nor sucrose accumulation was altered, suggesting that ShF5H1 overexpression would not affect first-generation ethanol production. Interestingly, the bagasse showed a significantly higher fiber content. Our results indicate that the tissue-specific manipulation of the biosynthetic branch leading to S unit formation is industrially advantageous and has established a foundation for further studies aiming at refining lignin modifications. Thus, the ShF5H1 overexpression in sugarcane emerges as an efficient strategy to improve 2GE production from straw.

KEYWORDS:

• Bioenergy
• ferulate 5-hydroxylase
• lignocellulose
• monolignol
• saccharum spp

Acknowledgments

We acknowledge Prof. Dr. Fredy Altpeter for kindly providing the pJFNPTII vector and for advice on sugarcane genetic transformation; William Cursino for technical support in plant maintenance in the greenhouse; Nathalia Takahashi, Paulo Henrique da Silva Santos and William Cursino for supporting the growth analysis in the greenhouse; Oseias Duarte for supporting the determination of sugar and fiber content in the culm; Jéssica Letícia da Silva Freiria and Tatiana Takahasi Komoto for technical support on tissue culture; Raul Lima Coasaca for technical support on data analysis and statistics; Prof. Dr. Maria Helena Goldman for expression cassette construction and sequencing support; Dr. José Bressiani and Hugo Soriano (Nuseed Brazil company) for sending samples of L6 transgenic line from field experimentation; Dr. Marina C M Martins Soldi from In Press Scientific Consulting and Communication Services for editing our manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

Juan Pablo Portilla Llerena: Methodology, Formal analysis, Investigation, Writing – Original Draft, Writing – Review & Editing. Eduardo Kiyota: Methodology. Fernanda Raquel Camilo dos Santos: Methodology. Julio C. Garcia: Methodology. Michael dos Santos Brito: Conceptualization. Rodrigo Faleiro de Lima: Methodology, Formal analysis, Writing. Juliana Lischka Sampaio Mayer: Methodology, Formal analysis, Writing. Paulo Mazzafera: Conceptualization, Writing – Review & Editing, Resources. Silvana Creste: Conceptualization, Writing – Review & Editing, Resources. Paula Macedo Nobile: Conceptualization, Writing – Original Draft, Writing – Review & Editing, Methodology, Formal analysis, Investigation, Supervision, Project administration, Funding acquisition. All authors read and approved the final version of the manuscript.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/21645698.2024.2325181

Additional information

Funding

This research was supported by the São Paulo Research Foundation [FAPESP - grant 2013/19214-0 and grant 2020/07045-3]. Fapesp also granted fellowships to PMN [grant 14/09422-8], MSB [grant 14/23017-9], and JPPL [grant 18/25058-5]. PM received a research fellowship from the Brazilian National Council for Scientific and Technological Development (CNPq).