Matthews, M. A. | bioRxiv Science

bioRxiv2024

Grape ripening speed slowed down using natural variation

Understanding ripening patterns and governing ripening speed are central aspects of grapevine (Vitis vinifera) berry biology owing to the importance of grape ripeness in winemaking. Despite this, the genetic control of ripening is largely unknown. Here, we report a major quantitative trait locus that controls ripening speed, expressed as speed of sugar accumulation. A haplotype originating from the species Vitis riparia halves maximum speed regardless of crop levels and berry sizes. The sequence of events that are normally completed at the onset of ripening in a two-week period known in viticulture as veraison are taking place at a slower speed, thereby attaining ripeness under milder weather conditions in late summer. V. vinifera cultivars show limited phenotypic variation for ripening speed and no selective sweep in the causal genomic region that could derive from domestication or improvement. Closely related species make up for the lack of standing variation, supplying major effect alleles for adapting grape cultivars to climate change. HIGHLIGHT / SIGNIFICANCE STATEMENTReducing the speed of fruit ripening genetically is a means for adapting the grape berry developmental program to the changing needs of the wine industry and in response to global warming. We identified a haplotype in a wild grape species that slows down the speed of ripening in progenies of Vitis vinifera by limiting the speed of sugar accumulation throughout the duration of ripening, a condition of great importance for winemakers to harvest their grapes at the desired level of technological ripeness.

plant biology↗

bioRxiv2019

Minimally invasive, pressure probe based sampling allows for in-situ gene expression analyses in plant cells.

BackgroundGene expression analyses are conducted using multiple approaches and increasingly research has been focused on assessing gene expression at the level of a tissue or even single-cells. To date, methods to assess gene expression at the single-cell in plant tissues have been semi-quantitative, require tissue disruption, and/or involve laborious, possibly artifact-inducing manipulation. In this work, we used grape berries (Vitis vinifera L. Zinfandel) as a model in order to examine the validity and reproducibility of an in-situ gene expression analysis method combining a cell pressure probe (CPP) with quantitative PCR (qPCR).\n\nResultsWe developed a method to directly assess gene expression levels via qPCR from cellular fluids sampled in-situ with a CPP. Cellular fluids, with volumes in the picoliter range, were collected from intact berries with a CPP at various depths across skin and mesocarp tissues. The expression of a key anthocyanin biosynthetic gene, UDP-glucose: flavonoid 3-O-glucosyltransferase (VviUFGT), was analyzed as a test case since its expression is restricted to cells producing anthocyanins in grape berry skins during ripening. The method identifies samples contaminated with significant levels of genomic DNA by amplifying a region of VviUFGT that spans an intron. Therefore false positives were discarded which occurred in 28% of the samples tested. Shallow probing of skin cells showed high VviUFGT expression as expected while deeper probing of mesocarp cells resulted in no VviUFGT expression.\n\nConclusionsThe clear correspondence of VviUFGT expression to the targeted cell samples suggests that the in-situ gene expression analysis using a CPP is reliable and does not result in contamination as the probe moves through tissues. This method can be paired to single-cell transcriptomic analyses in the future. We conclude that this technique represents a minimally invasive method of sampling plant cells in-situ which creates an opportunity for the analysis of cellular level, spatiotemporal responses in heterogeneous plant tissues.

plant biology↗