Identification of the Genetic Basis of Response to de-Acclimation in Winter Barley

Abstract

Mechanisms involved in the de-acclimation of herbaceous plants caused by warm periods during winter are poorly understood. This study identifies the genes associated with this mechanism in winter barley. Seedlings of eight accessions (four tolerant and four susceptible to de-acclimation cultivars and advanced breeding lines) were cold acclimated for three weeks and de-acclimated at 12 °C/5 °C (day/night) for one week. We performed differential expression analysis using RNA sequencing. In addition, reverse-transcription quantitative real-time PCR and enzyme activity analyses were used to investigate changes in the expression of selected genes. The number of transcripts with accumulation level changed in opposite directions during acclimation and de-acclimation was much lower than the number of transcripts with level changed exclusively during one of these processes. The de-acclimation-susceptible accessions showed changes in the expression of a higher number of functionally diverse genes during de-acclimation. Transcripts associated with stress response, especially oxidoreductases, were the most abundant in this group. The results provide novel evidence for the distinct molecular regulation of cold acclimation and de-acclimation. Upregulation of genes controlling developmental changes, typical for spring de-acclimation, was not observed during mid-winter de-acclimation. Mid-winter de-acclimation seems to be perceived as an opportunity to regenerate after stress. Unfortunately, it is competitive to remain in the cold-acclimated state. This study shows that the response to mid-winter de-acclimation is far more expansive in de-acclimation-susceptible cultivars, suggesting that a reduced response to the rising temperature is crucial for de-acclimation tolerance.

Transcriptome Analysis of Diurnal and Nocturnal-Warmed Plants, the Molecular Mechanism Underlying Cold Deacclimation Response in Deschampsia antarctica

“…The relationship between the consumption of accumulated soluble carbohydrates, with the activation of photosynthetic metabolism and vegetative growth, has been previously associated with the cold deacclimation process [ 16 , 21 , 68 ]. Usually, cold deacclimation occurs during the spring season, and for some species, it could be a passive process [ 17 ]. However, D. antarctica plants should maintain their freezing tolerance for the whole year, since they need to deal with freezing temperatures during the growing season (summer) [ 11 , 12 ].…”

“…However, D. antarctica plants should maintain their freezing tolerance for the whole year, since they need to deal with freezing temperatures during the growing season (summer) [ 11 , 12 ]. Therefore, when cold deacclimation occurs in D. antarctica (at least 7 °C increase in LT 50 ), it was promoted by nocturnal warming [ 14 ], and this should be an active process, as was also proposed by Wójcik-Jagła et al [ 17 ] for winter barley submitted to warm periods during the winter season. This active cold deacclimation process involves a complex gene regulation that was activated by nocturnal warming only, as has been shown in this laboratory study.…”

“…Cold deacclimation entails the partial or total loss of previously acquired freezing tolerance traits [ 15 ], and is not just a passive reversal of cold acclimation, but rather a genetically and functionally distinct process [ 16 , 17 ]. Even though various studies have analyzed the cold deacclimation profile after a temperature increase in several species ( Arabidopsis thaliana , Brassica napus , Hordeum vulgare , Rhododendron anthopogon , among others [ 17 , 18 , 19 , 20 ]), and identified up- and down-regulated genes during this process, they have not differentiated between the effects of diurnal or nocturnal temperature increments. In addition, the cold deacclimation dynamic could change among species [ 21 ], as well as the gene expression associated with this process.…”

How Does Diurnal and Nocturnal Warming Affect the Freezing Resistance of Antarctic Vascular Plants?

“…Therefore, given that diurnal warming per se does not affect the relative abundance of the dehydrin-like proteins detected in D. antarctica , it could be inferred that DW+ has little effect on the cold deacclimation induction in this species, at least in the current experimental condition. In the same line of thought, it could be expected that nocturnal warming with minimum night temperatures above the deacclimation threshold, downregulated the transcription factors required for dehydrin expression as it happens in Hordeum vulgare and Rhododendron anthopogon plants [ 57 , 58 ], as well as other proteins related to freezing tolerance, such as apoplastic ice recrystallization inhibition proteins (IRIP) [ 15 , 59 , 60 ]. A prominent candidate to regulate the expression of these genes is CBF transcription factor, which conforms a regulon that controls the expression of genes necessary for cold acclimation and freezing tolerance [ 61 , 62 , 63 , 64 ].…”