Submitted to: Horticulture Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2018
Publication Date: 3/1/2018
Citation: Londo, J.P., Kovaleski, A.P., Lillis, J.A. 2018. Divergence in the transcriptional landscape between low temperature and freeze shock in cultivated grapevine (Vitis vinifera). Horticulture Research. 5(10). https://doi.org/10.1038/s41438-018-0020-7.
DOI: https://doi.org/10.1038/s41438-018-0020-7

Interpretive Summary: Grapevines can suffer damage from freezing and frost events during the winter and spring seasons. Frost damage is particularly problematic as green growing tissues have very little defense against freezing temperatures. In other plant species, exposure to low, non-freezing temperatures often increases freeze resistance. This study was conducted to test this in grapevine, and to evaluate how grapevine genes are changing in response to cold temperatures. Exposure to low temperatures did not result in damage to grapevine, though freezing temperature caused variable damage to young leaves. At the gene expression level, major differences were observed between leaves exposed to low temperature compared with freezing conditions. Several important hormone pathways (e.g. ethylene, abscisic acid) were regulated very different in these conditions, as were several major families of transcription factors related to stress response (e.g. AP2/ERF, WRKY, NAC). The pathways controlling sugar metabolism seem to indicate that starch accumulation occurs in response to all cold treatments, but that activation of raffinose metabolism is specific to freezing conditions. Taken together, these results demonstrate that low temperature and freezing stresses affect grapevine metabolism in very different ways. Identification of freeze specific genes and pathways will allow us to further understand and identify essential candidate genes to be used by grapevine researchers and breeders to increase freeze resistance in the future.

Technical Abstract: Low temperature stresses limit the sustainability and productivity of grapevines when early spring frosts damage young grapevine leaves. Spring conditions often expose grapevines to low, but not damaging, chilling temperatures and these temperatures have been shown to increase freeze resistance in other model systems. In this study we examined whole transcriptome gene expression patterns of young leaf tissue from 5 different grapevine cultivars, exposed to chill and freeze shock, in order to understand the underlying transcriptional landscape associated with cold stress response. No visible damage was observed when grapevine leaves were exposed to chilling temperatures while freeze temperatures resulted in variable damage in all cultivars. Significant differences in gene expression were observed between warm control conditions and all types of cold stress. Exposure to chill stress (4 °C) versus freezing stress (-3 °C) resulted in very different patterns of gene expression and enriched pathway responses. Genes from the ethylene signaling, ABA signaling, the AP2/ERF, WRKY, and NAC transcription factor families, and Starch/Sucrose/Galactose pathways were among the most commonly observed to be differentially regulated. Preconditioning leaves to chill temperatures prior to freezing temperatures resulted in slight buffering of gene expression responses, suggesting that differences between chill and freeze shock perception complicates identification of candidate genes for cold resistance in grapevine. Overall, the transcriptional landscape contrasts observed between low temperature and freezing stresses demonstrate very different activation of candidate pathways impacting grapevine cold response.