Project description:The interplay between environmental and genetic factors conditions the fruit ripening program in plants. Transcriptome analysis of grapevine fruits can help understanding these interactions to consciously cope with conditions leading to detrimental effects for viticultural purposes. However, considering the grapevine characteristic ripening asynchrony, which can be intensified by contrasting conditions, accurate grape sampling may be essential for molecular comparisons. In this study, berry density sorting according to floatability in NaCl solutions was assessed as a grape ripening staging strategy. Total sugar content was more correlated with berry density than with other non-invasive ripening parameters. The transcriptome was compared between three density classes collected near commercial maturity using grapevine whole-genome NimbleGen microarrays. Expression profiles clearly related with ripening progression were detected in a density series simultaneously collected from a vineyard of Albariño. By contrast, considerable differences were detected when the same density series was sampled on two different dates from the same vineyard of Tempranillo. Functional analysis indicated that environmental differences between both sampling moments determined most of these expression differences. Ripening degree-dependent responses to the environment were also detected. Finally, the effect of the sorting procedures on the grape transcriptome showed negligible when it was directly tested. Altogether, these findings evidence the convenience of homogenizing the developmental stage and the sampling time conditions for transcriptome comparisons. Berry density sorting proved useful to this end, although this method could be limited when the berry sugar concentration is not determined by the ripening developmental program. The potential berry transcriptional response to the high concentrated salt solutions used for berry density-sorting may involve a concern on the suitability of this method for transcriptomic studies. This possibility was directly tested by comparing the expression of berries immersed in a highly concentrated NaCl solution (170 g•L-1) during a relatively long time lapse (1 h) with that in berries kept at room air. This experiment was carried out using Tempranillo grapes at mid-véraison to standardize the ripening state by selecting berries with the same proportion of coloured skin surface (50%, corresponding to TSS of 9.9 ±0.3 ºBrix). Berries grown under watering (W) and no-watering (NW) conditions were analysed to test for possible irrigation-NaCl solution interactions affecting berry gene expression. No significant DEG was identified when the effect of the NaCl solution was analysed separately for berries collected from W or NW blocks (≥2-fold change and B-H adjusted P≤0.05 in 2-class limma). When W and NW samples were used together to analyse the effect of the NaCl immersion irrespectively of the irrigation treatment, 15 genes were detected with a B-H adjusted P≤0.05 and only 13 of these showed ≥2-fold change, confirming the slight effect. In summary, the effect of the NaCl immersion on the berry transcriptome is negligible and does not seem to interact with the transcriptomic response to other environmental cues.
Project description:Somatic variation is a valuable source of trait diversity in clonally propagated crops. In grapevine, which has been clonally propagated worldwide for centuries, important phenotypes such as white berry colour are the result of genetic changes caused by transposable elements. Additionally, epiallele formation may play a role in determining geo-specific (‘terroir’) differences in grapes and thus ultimately in wine. This genomic plasticity might be co-opted for crop improvement via somatic embryogenesis, but that depends on a species-specific understanding of the epigenetic regulation of transposable element (TE) expression and silencing in these cultures. For this reason, we used whole-genome bisulphite sequencing, mRNA sequencing and small RNA sequencing to study the epigenetic status and expression of TEs in embryogenic callus, in comparison with leaf tissue.
Project description:By implementing a leaf-removal treatment in the berry bunch zone, grapes were predominantly exposed to elevated light and their complete transcriptomes (as generated by RNASeq) were compared at four developmental stages.