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X-ray phase contrast imaging of Vitis spp. buds shows freezing pattern and correlation between volume and cold hardiness.

ABSTRACT: Grapevine (Vitis spp.) buds must survive winter temperatures in order to resume growth when suitable conditions return in spring. They do so by developing cold hardiness through deep supercooling, but the mechanistic process of supercooling in buds remains largely unknown. Here we use synchrotron X-ray phase contrast imaging to study cold hardiness-related characteristics of V. amurensis, V. riparia, and V. vinifera buds: time-resolved 2D imaging was used to visualize freezing; and microtomography was used to evaluate morphological changes during deacclimation. Bud cold hardiness was determined (low temperature exotherms; LTEs) using needle thermocouples during 2D imaging as buds were cooled with a N₂ gas cryostream. Resolution in 2D imaging did not allow for ice crystal identification, but freezing was assessed by movement of tissues coinciding with LTE values. Freezing was observed to propagate from the center of the bud toward the outer bud scales. The freezing events observed lasted several minutes. Additionally, loss of supercooling ability appears to be correlated with increases in bud tissue volume during the process of deacclimation, but major increases in volume occur after most of the supercooling ability is lost, suggesting growth resumption processes are limited by deacclimation state.

SUBMITTER: Kovaleski AP

PROVIDER: S-EPMC6802181 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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X-ray phase contrast imaging of Vitis spp. buds shows freezing pattern and correlation between volume and cold hardiness.

Kovaleski Alisson P AP Londo Jason P JP Finkelstein Kenneth D KD

Scientific reports 20191018 1

Grapevine (Vitis spp.) buds must survive winter temperatures in order to resume growth when suitable conditions return in spring. They do so by developing cold hardiness through deep supercooling, but the mechanistic process of supercooling in buds remains largely unknown. Here we use synchrotron X-ray phase contrast imaging to study cold hardiness-related characteristics of V. amurensis, V. riparia, and V. vinifera buds: time-resolved 2D imaging was used to visualize freezing; and microtomograp ...[more]

PMID: 31628356

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Project description:Background and aimsIt has been reported that low temperatures (LTs) and the plant hormone abscisic acid (ABA) induce the expression of CBF/DREB1 transcription factors in vegetative tissues and seedlings of Vitis vinifera and Vitis riparia and that foliar applications of ABA to V. vinifera increase the freezing tolerance or cold-hardiness of dormant buds. However, the combined effect of ABA and LTs on the expression of CBF/DREB1 transcription factors and on the acquisition of freezing tolerance in dormant grapevine buds has not been investigated. The objective of this study was to analyse the combined effect of ABA and LT treatments on the expression of CBF/DREB transcription factors and the acquisition of freezing tolerance.MethodsIn vitro experiments with single-bud cuttings of grapevines were used to analyse the effect of ABA, ABA + LT and LT on the expression of CBF/DREB transcription factors, dehydrin and antioxidant genes, the acquisition of freezing tolerance and the endogenous content of ABA. Gene expression analysis was performed by quantitative real-time PCR and freezing tolerance was determined by measuring the low-temperature exotherm by differential thermal analysis. ABA levels were determined by gas chromatography coupled to an electron capture detector.Key resultsThe LT treatment and exogenous application of ABA to grapevine dormant buds increased the expression of the CBF/DREB1 transcription factors VvCBF2, VvCBF3, VvCBF4 and VvCBF6. The joint application of LT and ABA produced a huge increase in the expression of these transcription factors, which was greater than the sum of the increases produced by them individually, which indicates the existence of a synergistic effect between ABA and LT on the activation of these transcription factors. This synergic effect was also observed on the increase in bud cold-hardiness and on the expression of antioxidant and dehydrin genes.ConclusionsThe synergy between ABA and LT on the expression of CBF/DREB1 transcription factors VvCBF2, VvCBF3, VvCBF4 and VvCBF6 plays a key role in cold acclimatization of grapevine buds. The results highlight the importance of the combination of stimuli in the improvement of genetic and physiological responses and help us to understand the adaption of plants to complex environments.

Project description:Significant advances have been made in our understanding of the regulation of cold hardiness. The existence of numerous biophysical and biochemical adaptive mechanisms in perennial woody plants and the complexity their regulation has made the development of methods for managing and improving cold hardiness in perennial woody plants has been very difficult. This may be partially attributed to viewing cold hardiness as a single dimensional response, rather than as a complex phenomenon, involving different mechanisms (avoidance and tolerance), different stages (mid-winter vs. late winter), and having an intimate overlap with the genetic regulation of dormancy. In particular separating the molecular regulation of cold hardiness from growth processes has been challenging. ICE and C-repeat binding factor (CBF), transcription factors (Inducer of CBF expression and CRT-binding factor) have been shown to be an important aspect in the regulation of cold-induced gene expression. Evidence has emerged, however, that they are also intimately involved in the regulation of growth, flowering, dormancy, and stomatal development. This evidence includes the presence of CBF binding motifs in genes regulating these processes, or through cross-talk between the pathways that regulate them. Recent changes in climate that have resulted in erratic episodes of unseasonal warming followed by more seasonal patterns of low temperatures has also highlighted the need to better understand the genetic and molecular regulation of deacclimation, a topic of research that is only more recently being addressed. Environmentally-induced epigenetic regulation of stress responses and seasonal processes such as cold acclimation, deacclimation, and dormancy have been documented but are still poorly understood. Advances in the ability to efficiently generate large DNA and RNA datasets and genetic transformation technologies have greatly increased our ability to explore the regulation of gene expression and explore genetic diversity. Greater knowledge of the interplay between epigenetic and genetic regulation of cold hardiness, along with the application of advanced genetic analyses, such as genome-wide-association-studies (GWAS), are needed to develop strategies for addressing the complex processes associated with cold hardiness in woody plants. A cautionary note is also indicated regarding the time-scale needed to examine and interpret plant response to freezing temperatures if progress is to be made in developing effective approaches for manipulating and improving cold hardiness.

Project description:Chickpea is one of the most important grain legume crops in the world. India is the largest producer, consumer as well as importer of chickpea. Cold stress (temperature < 15 °C) is one of the important abiotic stresses limiting chickpea production by hampering its growth and vigor at all phenological stages. This study was aimed to characterize a diverse set of 366 chickpea genotypes for cold tolerance and identify most promising cold tolerant chickpea genotypes in the Western-Himalayas of Jammu and Kashmir, India. The 366 genotypes used during the present study including genotypes belonging to cultivated, primary and secondary gene pools of chickpea. Two important approaches were used including visual screening under field conditions and screening under controlled conditions by measuring cell membrane stability through electrolyte leakage tests. The analysis of trait data collected through both the approaches led to the identification of five most promising/candidate cold tolerant chickpea genotypes including one wild genotype "Ortan-066" from secondary gene pool species (C. echinospermum), one wild genotype "Cudi 1-022" from primary gene pool species (C. reticulatum) and three genotypes (IC 116783, ICC 15200 and AGBLG 170004) from the cultivated species (Cicer arietinum). Wild genotype "Ortan-066" was found best cold tolerance source with the mean Cold Tolerance Rating (CTR) of 2 and Electrolyte Leakage Index (ELI) of 10.82%, followed by wild genotype "Cudi 1-022" (CTR = 3, ELI = 18.89%), and three cultivated genotypes viz., IC 116783, ICC 15200 and AGBL-G-170004, with the mean CTR of 3 and an estimated mean ELI of 21.26%, 21.58% and 21.94%, respectively. The promising, candidate cold tolerant genotypes identified during the present study could be used in chickpea breeding programs aimed at improving cold tolerance of cultivated chickpea worldwide. The candidate lines can be also used for developing bi-parental mapping populations, wild × cultivated introgression lines, transcriptomics and for differential expression analysis of cold tolerant genes in chickpea.Supplementary informationThe online version contains supplementary material available at 10.1007/s12298-021-00997-1.

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X-ray phase contrast imaging of Vitis spp. buds shows freezing pattern and correlation between volume and cold hardiness.

Publications

X-ray phase contrast imaging of Vitis spp. buds shows freezing pattern and correlation between volume and cold hardiness.

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