Day and night heat stress trigger different transcriptomic responses in green and ripening grapevine (vitis vinifera) fruit

Background: Global climate change will noticeably affect plant vegetative and reproductive development. The recent increase in temperatures has already impacted yields and composition of berries in many grapevine-growing regions. Physiological processes underlying temperature response and tolerance of the grapevine fruit have not been extensively investigated. To date, all studies investigating the molecular regulation of fleshly fruit response to abiotic stress were only conducted during the day, overlooking possible critical night-specific variations. The present study explores the night and day transcriptomic response of grapevine fruit to heat stress at several developmental stages. Short heat stresses (2 h) were applied at day and night to vines bearing clusters sequentially ordered according to the developmental stages along their vertical axes. The recently proposed microvine model (DRCF-Dwarf Rapid Cycling and Continuous Flowering) was grown in climatic chambers in order to circumvent common constraints and biases inevitable in field experiments with perennial macrovines. Post-véraison berry heterogeneity within clusters was avoided by constituting homogenous batches following organic acids and sugars measurements of individual berries. A whole genome transcriptomic approach was subsequently conducted using NimbleGen 090818 Vitis 12X (30 K) microarrays. Results: Present work reveals significant differences in heat stress responsive pathways according to day or night treatment, in particular regarding genes associated with acidity and phenylpropanoid metabolism. Precise distinction of ripening stages led to stage-specific detection of malic acid and anthocyanin-related transcripts modulated by heat stress. Important changes in cell wall modification related processes as well as indications for heat-induced delay of ripening and sugar accumulation were observed at véraison, an effect that was reversed at later stages. Conclusions: This first day - night study on heat stress adaption of the grapevine berry shows that the transcriptome of fleshy fruits is differentially affected by abiotic stress at night. The present results emphasize the necessity of including different developmental stages and especially several daytime points in transcriptomic studies

Identification of stable QTLs for vegetative and reproductive traits in the microvine (Vitis vinifera L.) using the 18 K Infinium chip

UMR AGAP - équipe DAAV - Diversité, adaptation et amélioration de la vigne[b]Background[/b] [br/]The increasing temperature associated with climate change impacts grapevine phenology and development with critical effects on grape yield and composition. Plant breeding has the potential to deliver new cultivars with stable yield and quality under warmer climate conditions, but this requires the identification of stable genetic determinants. This study tested the potentialities of the microvine to boost genetics in grapevine. A mapping population of 129 microvines derived from Picovine x Ugni Blanc flb, was genotyped with the Illumina® 18 K SNP (Single Nucleotide Polymorphism) chip. Forty-three vegetative and reproductive traits were phenotyped outdoors over four cropping cycles, and a subset of 22 traits over two cropping cycles in growth rooms with two contrasted temperatures, in order to map stable QTLs (Quantitative Trait Loci). [br/][b]Results[/b] [br/]Ten stable QTLs for berry development and quality or leaf area were identified on the parental maps. A new major QTL explaining up to 44 % of total variance of berry weight was identified on chromosome 7 in Ugni Blanc flb, and co-localized with QTLs for seed number (up to 76 % total variance), major berry acids at green lag phase (up to 35 %), and other yield components (up to 25 %). In addition, a minor QTL for leaf area was found on chromosome 4 of the same parent. In contrast, only minor QTLs for berry acidity and leaf area could be found as moderately stable in Picovine. None of the transporters recently identified as mutated in low acidity apples or Cucurbits were included in the several hundreds of candidate genes underlying the above berry QTLs, which could be reduced to a few dozen candidate genes when a priori pertinent biological functions and organ specific expression were considered. [br/][b]Conclusions[/b] [br/]This study combining the use of microvine and a high throughput genotyping technology was innovative for grapevine genetics. It allowed the identification of 10 stable QTLs, including the first berry acidity QTLs reported so far in a Vitis vinifera intra-specific cross. Robustness of a set of QTLs was assessed with respect to temperature variatio

A highly efficient embryo rescue protocol to recover a progeny from of the microvine

International audienceThe grapevine is a difficult species for genetic studies due to the plant size and long life cycle. With the microvine, these limitations can be overcome thanks to its dwarf stature, continuous flowering, short juvenile phase and generation cycle. The advantages of the microvine allow scientists to undertake genetic studies 2-5 times more rapidly than the current situation with normal grapevines. However, the seeds obtained from microvine parents have a low germination rate, and therefore some approaches to improve seed germination are required. Four microvine lines (ML1, V19, Pico x FLB 225, and AB x ML1) and a classical grapevine variety (‘Syrah’ cl. 174) were experimented in embryo rescue experiments. To evaluate embryo germination rate during berry development, seeds were collected from four different berry developmental stages including 2 weeks before veraison (WBV), veraison, 3 and 6 weeks after veraison (WAV). For all microvine varieties, the age of seed or berry stage influenced the development of the embryos. The highest percentage of germinating embryos (100 %) and normal developed plantlets (100 %) were recorded at veraison stage followed by 2 WBV, 3 WAV and 6 WAV, respectively. In addition, growth and development of embryos derived from veraison berries were also faster than the other phases. This study concluded that veraison is the most suitable berry developmental stage for microvine embryo extraction and culture, whereas, the best stage for embryo rescue in ‘Syrah’ grapevine is 2 WBV. The information obtained from this experiment will be useful for microvine breeding programs and expand their germplasm base in the future

A highly efficient embryo rescue protocol to recover a progeny from the microvine

The grapevine is a difficult species for genetic studies due to the plant size and long life cycle. With the microvine, these limitations can be overcome thanks to its dwarf stature, continuous flowering, short juvenile phase and generation cycle. The advantages of the microvine allow scientists to undertake genetic studies 2-5 times more rapidly than the current situation with normal grapevines. However, the seeds obtained from microvine parents have a low germination rate, and therefore some approaches to improve seed germination are required. Four microvine lines (ML1, V19, Pico x FLB 225, and x ML1) and a classical grapevine variety ('Syrah' cl. 174) were experimented in embryo rescue experiments. To evaluate embryo germination rate during berry development, seeds were collected from four different berry developmental stages including 2 weeks before veraison (WBV), veraison, 3 and 6 weeks after veraison (WAY). For all microvine varieties, the age of seed or berry stage influenced the development of the embryos. The highest percentage of germinating embryos (100 %) and normal developed plantlets (100 %) were recorded at veraison stage followed by 2 WBV, 3 WAV and 6 WAV, respectively. In addition, growth and development of embryos derived from veraison berries were also faster than the other phases. This study concluded that veraison is the most suitable berry developmental stage for microvine embryo extraction and culture, whereas, the best stage for embryo rescue in `Syrah' grapevine is 2 WBV. The information obtained from this experiment will be useful for microvine breeding programs and expand their germplasm base in the future

The microvine provides new perspectives for research on berry physiology: La microvigne ouvre de nouvelles perspectives aux recherches sur la physiologie du raisin

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Temperature impacts on grapevine physiology and development at both plant and organ levels

International audienc

Microvine: A New Model to Study Grapevine Growth and Developmental Patterns and their Responses to Elevated Temperature

Growing standardized plant material in controlled environment can facilitate the disentangling of the many impacts of climate change on grapevine production and quality. Microvine is a natural gibberellic acid insensitive mutant showing dwarfism, early and continuous flowering along the vegetative axes. It was initially proposed as a model for genetics. In this study, we questioned its suitability to facilitate and hasten the characterization of grapevine vegetative and reproductive growth and development patterns as wells as their responses to temperature elevation. A series of experiments were performed in the greenhouse and in growth chambers under either ‘standard’ (25/15°C days/night) or contrasted (from 22/12°C up to 30/25°C) thermal treatments for several weeks. Under ‘standard’ thermal condition, measured temporal patterns of leaf and berry growth were similar among several phytomers along the main axis allowing us to estimate temporal growth patterns from spatial distribution of organ size. These patterns were stable between independent experiments under similar thermal and irradiance conditions. When plants were exposed to contrasted thermal treatments, leaf emergence rate was found linearly related to average daily temperature allowing us to derive a thermal time based model of development. Under cool thermal conditions (22/12°C), the temporal evolution of biochemical parameters was similar to that classically found for grapevine. However, exposing plants to a + 8°C thermal treatment for 450 °Cd revealed strong alterations of the thermal time based developmental program with either acceleration (leaf and internode growth) or delay (flowering, sugar accumulation in berries), as well as major uncoupling between growth and storage in internodes. These results reveal the potential of Microvine to study grapevine responses to the many facets of climate change.Bases développementales, moléculaires et génétiques de l'adaptation de la vigne à la contrainte thermique

The development of genetics tools for the selection of grapevine wine cultivars adapted to warming

International audienc