Effect of the Winter Wheat Cheyenne 5A Substituted Chromosome on Dynamics of Abscisic Acid and Cytokinins in Freezing-Sensitive Chinese Spring Genetic Background.

Balázs Kalapos,Ferenc Marincs,Pavel Vítámvás,Aliz Novák,Gábor Galiba,Radomira Vanková,Petre Dobrev

doi:10.3389/fpls.2017.02033

Abstract

The effect of short- and long-term cold treatment on the abscisic acid (ABA) and cytokinin (CK) metabolism, and their main biosynthesis- and signaling-related genes were investigated in freezing-sensitive and freezing-tolerant wheat genotypes. Varieties Cheyenne and Chinese Spring substituted with the 5A Cheyenne chromosome, which represented freezing-tolerant genotypes, were compared with the freezing-sensitive Chinese Spring. Hormone levels and gene expression data indicated that the short- and long-term cold treatments are associated with specific regulation of the accumulation of cold-protective proteins and phytohormone levels, as well as the expression profiles of the hormone-related genes. The significant differences were observed between the genotypes, and between their leaf and crown tissues, too. The level of dehydrins, including WCS120 protein, and expression of WCS120 gene were considerably higher in the freezing-tolerant genotypes after 21 days of cold treatment. Expression of Cor14b and CBF14, cold-responsive regulator genes, was increased by cold treatment in all genotypes, to higher extent in freezing-tolerant genotypes. Cluster analysis revealed that the tolerant genotypes had a similar response to cold treatment, regarding expression of the ABA and CK metabolic genes, as well as hormone levels in leaves. As far as hormone levels in crowns are concerned, however, the strongly freezing-tolerant Cheyenne variety clustered separately from the Chinese Spring and the substitution line, which were more similar to each other after both 1 and 21 days of cold treatment than to Cheyenne. Based on these results we concluded that the 5A chromosome of wheat might have both a direct and an indirect impact on the phytohormone-dependent cold-induced freezing tolerance. Based on the gene expression data, novel genetic markers could be developed, which may be used to determine the freezing tolerance level in a wide range of wheat varieties.

Highlights

One of the major cereals at present is the hexaploid (AABBDD genomes) Triticum aestivum or common wheat (Dubcovsky and Dvorak, 2007), which combines the D genome from Aegilops tauschii with the AB genomes from tetraploid wheat and exhibits a broader adaptability to different environmental conditions in comparison with its predecessors
In order to characterize the differences in cold stress responses among the studied genotypes and to prove the role of the chromosome 5A of Cheyenne in the improvement of freezing tolerance in the Chinese Spring (CS) genetic background, expression profiles of four selected marker genes, VRN1 (Vernalization 1) (Figures 2A,B and Supplementary Table 2), CBF14 (C-repeat binding factor 14), Cor14b (Cold-responsive protein 14b) and
After 21 days, approximately 5- and 3-fold increase in VRN1 expression was detected in CS and CS(Ch5A) leaves, respectively, but only a low, non-significant elevation was detected in Cheyenne

Summary

Introduction

One of the major cereals at present is the hexaploid (AABBDD genomes) Triticum aestivum or common wheat (Dubcovsky and Dvorak, 2007), which combines the D genome from Aegilops tauschii with the AB genomes from tetraploid wheat and exhibits a broader adaptability to different environmental conditions in comparison with its predecessors. Common wheat tolerates the absence of one chromosome from any pair, without losing its fertility. This unique feature made it possible to develop a series of nullisomic lines from a moderate freezing-tolerant spring variety Chinese Spring (CS) (Sears, 1953). Using this nullisomic series, intervarietal chromosome substitution lines were created. In each of the substitution lines, one chromosome pair from the CS was replaced by the corresponding pair of chromosomes from the frost-resistant winter wheat variety Cheyenne (Ch). Replacing chromosome 5A of CS with the corresponding chromosome from Ch [CS(Ch5A)] increased the freezing tolerance of CS (Chen et al, 2009; Eagles et al, 2011)

Methods

Results

Conclusion