Carbohydrate Accumulation and Differential Transcript Expression in Winter Wheat Lines with Different Levels of Snow Mold and Freezing Tolerance after Cold Treatment.

Erika B Kruse,Daniel Z Skinner,Jesse Aplin,Arron H Carter,Samuel Revolinski,Timothy D Murray,Charles G Edwards

doi:10.3390/plants9111416

Erika B Kruse, Daniel Z Skinner + Show 5 more

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https://doi.org/10.3390/plants9111416

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Abstract

Winter wheat (Triticum aestivum L.) undergoes a period of cold acclimation in order to survive the ensuing winter, which can bring freezing temperatures and snow mold infection. Tolerance of these stresses is conferred in part by accumulation of carbohydrates in the crown region. This study investigates the contributions of carbohydrate accumulation during a cold treatment among wheat lines that differ in their snow mold tolerance (SMT) or susceptibility (SMS) and freezing tolerance (FrT) or susceptibility (FrS). Two parent varieties and eight recombinant inbred lines (RILs) were analyzed. The selected RILs represent four combinations of tolerance: SMT/FrT, SMT/FrS, SMS/FrT, and SMS/FrS. It is hypothesized that carbohydrate accumulation and transcript expression will differ between sets of RILs. Liquid chromatography with a refractive index detector was used to quantify carbohydrate content at eight time points over the cold treatment period. Polysaccharide and sucrose content differed between SMT and SMS RILs at various time points, although there were no significant differences in glucose or fructose content. Glucose and fructose content differed between FrT and FrS RILs in this study, but no significant differences in polysaccharide or sucrose content. RNAseq was used to investigate differential transcript expression, followed by modular enrichment analysis, to reveal potential candidates for other mechanisms of tolerance, which included expected pathways such as oxidative stress, chitinase activity, and unexpected transcriptional pathways. These differences in carbohydrate accumulation and differential transcript expression begin to give insight into the differences of wheat lines when exposed to cold temperatures.

Highlights

Winter wheat (Triticum aestivum L.) plants require a period of cold temperatures to shift from vegetative growth to reproductive growth, a transition known as vernalization
Concentration of polysaccharides, sucrose, glucose, and fructose were compared between tolerance categories and time points to detect a relationship that could suggest a role in tolerance to snow mold and freezing
Analysis of variance of the polysaccharide content of each recombinant inbred lines (RILs) at each time point showed no significant differences between the replicates (p = 0.68) or tolerance categories (p = 0.20), but significant differences existed between time points (p < 0.01) (Figure 1)

Summary

Introduction

Winter wheat (Triticum aestivum L.) plants require a period of cold temperatures to shift from vegetative growth to reproductive growth, a transition known as vernalization. To avoid cell death associated with freezing temperatures, winter wheat accumulates simple carbohydrates, including sucrose, glucose, and fructose, in the crown region, lowering the freezing point of the cell and enabling the plant to survive [4,5]. These carbohydrates serve as an energy source for the plant while photosynthesis is diminished due to cold temperatures and potential snow cover [4,6]. When there is snow cover, a diverse complex of fungal and fungal-like pathogens, referred to as ‘snow mold’ can take advantage of a plant’s carbohydrate stores for energy

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