Effect of mcl-PHA synthesis in flax on plant mechanical properties and cell wall composition

Magdalena Wróbel-Kwiatkowska,Jerzy Hanuza,Athanasios Beopoulos,Waldemar Rymowicz,Lucyna Dymińska,Jacek Żebrowski,Mateusz Kropiwnicki

doi:10.1007/s11248-018-0105-y

Abstract

The high demand for new biomaterials makes synthesis of polyhydroxyalkanoates (PHA) in plants an interesting and desirable achievement. Production of polymers in plants is an example of application of biotechnology for improving the properties of plants, e.g. industrial properties, but it can also provide knowledge about plant physiology and metabolism. The subject of the present study was an industrially important plant: flax, Linum usitatissimum L., of a fibre cultivar (cv Nike). In the study the gene encoding PHA synthase from Pseudomonas aeruginosa, fused to a peroxisomal targeting signal, was expressed in flax plants with the aim of modifying the mechanical properties of plants. Medium-chain-length (mcl) hydroxy acids in flax plants from tissue cultures were detected by GC-FID and FTIR method. The introduced changes did not affect fatty acid content and composition in generated flax plants. Since mcl-PHA are known as elastomers, the mechanical properties of created plants were examined. Modified plants showed increases in the values of all measured parameters (except strain at break evaluated for one modified line). The largest increase was noted for tensile stiffness, which was 2- to 3-fold higher than in wild-type plants. The values estimated for another parameter, Young’s modulus, was almost at the same level in generated flax plants, and they were about 2.7-fold higher when compared to unmodified plants. The created plants also exhibited up to about 2.4-fold higher tensile strength. The observed changes were accompanied by alterations in the expression of selected genes, related to cell wall metabolism in line with the highest expression of phaC1 gene. Biochemical data were confirmed by spectroscopic methods, which also revealed that crystallinity index values of cellulose in modified flax plants were increased in comparison to wild-type flax plants and correlated with biomechanical properties of plants.

Highlights

Polyhydroxyalkanoates (PHA) are natural origin, thermoplastic polyesters made up of (R)-3-hydroxy fatty acid monomers and synthesized by various bacteria species for energy and carbon storage, under nutrient limitation conditions (Ryu et al 1997; Valappil et al 2008)
The results showed that expression of selected genes from hemicellulose, lignin, and polyamine metabolism pathways were changed in transgenic flax lines (7, 11) when compared to wild type flax cv
Our investigations examined the possibility of polyhydroxy acid synthesis in flax to improve the plant mechanical properties

Summary

Introduction

Polyhydroxyalkanoates (PHA) are natural origin, thermoplastic polyesters made up of (R)-3-hydroxy fatty acid monomers and synthesized by various bacteria species for energy and carbon storage, under nutrient limitation conditions (Ryu et al 1997; Valappil et al 2008). Various plants are under investigation, including model plants such as Arabidopsis thaliana (Poirier et al 1992; Kourtz et al 2007) and crop plants, e.g. potato (Bohmert et al 2002; Romano et al 2005), tobacco (Nakashita et al 2001; Arai et al 2001; Suzuki et al 2002) and rape (Houmiel et al 1999; Valentin et al 1999) Attempts to produce these polymers in trees, i.e. poplar Populus ssp.

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