Fructan metabolism and changes in fructan composition during cold acclimation in perennial ryegrass.

Shamila W Abeynayake,Torben Asp,Stephen Byrne,Birte Boelt,Thomas P Etzerodt,Kristina JonaviäIenä—

doi:10.3389/fpls.2015.00329

Abstract

Perennial ryegrass (Lolium perenne L.) produces high levels of fructans as a mixture of oligosaccharides and polysaccharides with different degrees of polymerization (DP). The present study describes the analysis of the compositional changes in the full spectrum of fructans, fructan distribution between above ground biomass (top) and the roots, and the transcription of candidate genes involved in fructan metabolism during cold acclimation in perennial ryegrass variety “Veyo” and ecotype “Falster” from distinct geographical origins. We observed changes in fructan composition and induction of low-DP fructans, especially DP = 4, in both the top and the roots of “Veyo” and “Falster” in response to low-temperature stress. The accumulation of DP > 50 fructans was only apparent in the top tissues where the Lp1-FFT expression is higher compared to the roots in both “Veyo” and “Falster.” Our results also show the accumulation and depolymerization of fructans with different DP, together with the induction of genes encoding fructosyltransferases and fructan exohydrolases in both “Veyo” and “Falster” during cold acclimation, supporting the hypothesis that fructan synthesis and depolymerization occurring simultaneously. The ecotype “Falster,” adapted to cold climates, increased total fructan content and produced more DP > 7 fructans in the roots than the variety “Veyo,” adapted to warmer climates. This indicates that high-DP fructan accumulation in roots may be an adaptive trait for plant recovery after abiotic stresses.

Highlights

Changes in the content and composition of water-soluble carbohydrates in response to abiotic stresses are important metabolic re-adjustments in temperate grasses (Rao et al, 2011; Abdelgawad et al, 2014)
The present study focuses on the contents and compositional changes in the full spectrum of fructans and on the gene expression patterns of FTs and Fructan exohydrolases (FEHs) during cold acclimation in perennial ryegrass from distinct geographical origins
In “Veyo” roots, the fructan content increased only slightly to 54 and 50.8 mg/g at d 5 and d 9 and subsequently it decreased to levels similar to the initial level of 35 mg/g

Summary

Introduction

Changes in the content and composition of water-soluble carbohydrates in response to abiotic stresses are important metabolic re-adjustments in temperate grasses (Rao et al, 2011; Abdelgawad et al, 2014). Analysis of total fructan content alone, during the development of freezing tolerance does not provide information about the changes in fructan composition in response to low-temperature stresses and further there is a lack of knowledge about the effect of the fructan distribution between shoot and root tissues in contrasting ecotypes adapted to different climatic conditions (De Roover et al, 2000; Hisano et al, 2008; Rao et al, 2011). The present study focuses on the contents and compositional changes in the full spectrum of fructans and on the gene expression patterns of FTs and FEHs during cold acclimation in perennial ryegrass from distinct geographical origins. The relative quantification of fructans with different DPs was determined using high-resolution liquid chromatography– electrospray ionization TOF-MS (LC-ESI-TOF-MS) and gene expression analysis was performed using quantitative RT-PCR in both “Veyo” and “Falster” during cold acclimation

Materials and Methods

Results

Discussion