Temperature and Light-Quality-Dependent Regulation of Freezing Tolerance in Barley.

Ákos Boldizsár,Gábor Galiba,Pavel Vítámvás,Krisztián Gierczik,Mohamed Ahres

doi:10.3390/plants9010083

Abstract

It is established that, besides the cold, incident light also has a crucial role in the cold acclimation process. To elucidate the interaction between these two external hardening factors, barley plantlets were grown under different light conditions with low, normal, and high light intensities at 5 and 15 °C. The expression of the HvCBF14 gene and two well-characterized members of the C-repeat binding factor (CBF)-regulon HvCOR14b and HvDHN5 were studied. In general, the expression level of the studied genes was several fold higher at 5 °C than that at 15 °C independently of the applied light intensity or the spectra. The complementary far-red (FR) illumination induced the expression of HvCBF14 and also its target gene HvCOR14b at both temperatures. However, this supplementation did not affect significantly the expression of HvDHN5. To test the physiological effects of these changes in environmental conditions, freezing tests were also performed. In all the cases, we found that the reduced R:FR ratio increased the frost tolerance of barley at every incident light intensity. These results show that the combined effects of cold, light intensity, and the modification of the R:FR light ratio can greatly influence the gene expression pattern of the plants, which can result in increased plant frost tolerance.

Highlights

Cold acclimation is the prerequisite of overwintering for different plant species growing at temperate climates in the northern hemisphere
Under high light intensity (500 PAR) the plants showed greater survival rates than under low light conditions (20 PAR) even without cold hardening [58]. Our results showed this tendency as well, but our results showed that the decrease in the R:FR ratio exhibited a synergistic effect with low temperatures [23], but it triggered certain mechanisms at non-hardening temperatures, especially at high light intensity (350 PAR)
According to our best knowledge, these are the first results to show that the combined effects of cold, light intensity, and modification of the R:FR light ratio can greatly influence the expression pattern of HvCBF14 and HvCOR14b genes and can adjust the level of the HvDHN5 gene

Summary

Introduction

Cold acclimation is the prerequisite of overwintering for different plant species growing at temperate climates in the northern hemisphere. In order to achieve the genetically determined full winter hardiness, plants have developed different strategies [1]. Entering the period of dormancy is an essential strategy for perennial plants to survive harmful freezing conditions during winter [2]. Concerning the economically most important grasses like the cereals, they must go through a lengthy cold acclimation period, which requires the orchestration of transcriptional, biochemical, and physiological changes [3]. In both cases, cold acclimation is associated with decreasing the photoperiod and cessation of growth [4,5]. Accumulated evidence has elucidated that the “master gene(s)”

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