Paper Reviewed
Reineke, A. and Selim, M. 2019. Elevated atmospheric CO2 concentrations alter grapevine (Vitis vinifera) systemic transcriptional response to European grapevine moth (Lobesia botrana) herbivory. Scientific Reports 9: 2995, DOI:10.1038/s41598-019-39979-5.

Writing by way of introduction to their work, Reineke and Selim (2019) note that grapevine (Vitis spp.) is an important commodity crop cultivated in temperate regions around the world. And while many scientists have examined the effects of possible climate change on grapevine growth, very little is known about its potential combined response with insect herbivory under various future climate change scenarios. Thus, seeking to provide more information in this regard, the two German researchers set out to investigate the transcriptomic response of grapevine plants to insect herbivory from the European grapevine moth (Lobesia botrana).

The work was conducted at the Geisenheim Vineyard FACE facility at Geisenheim University, Germany. Two Vitis vinifera cultivars were used in the study (Riesling and Cabernet Sauvignon) and grown under ambient or elevated CO2 concentrations, the latter of which only amounted to a meager +58 ppm above ambient during daylight hours. At the "development of fruits" and "ripening of berries" stages, a subset of plants growing in the two CO2 treatments was subjected to herbivory by L. botrana. In this instance, five larvae were placed per grape bunch and were allowed to feed for four days. To prevent herbivore escape, nylon mesh bags were used to cover the grape bunches. Control plants also received nylon mesh bags, but without larvae infestation. Leaf samples were thereafter collected from both herbivore infected and non-infected leaves and subjected to transcriptome sequencing in order to assess if grapevine plants would show a differential transcriptomic response to herbivory based on CO2 concentration.

Results of the analysis revealed, in the words of the authors, that "grapevine transcriptional response to herbivory was clearly dependent on phenological stage, with a higher number of differentially expressed genes identified at fruit development compared to berry ripening." More specifically, they note that more transcripts were differentially expressed at fruit development as a response to herbivory under elevated compared to ambient CO2 concentrations. Furthermore, they report that "classification of the respective transcripts revealed that in particular genes involved in metabolic pathways, biosynthesis of secondary metabolites and plant-pathogen interactions were significantly enriched," adding that "most of these genes had similar expression patterns under both CO2 concentrations, with a higher fold-change under elevated CO2 concentrations."

Fortunately, many of the gene expression patterns observed at elevated CO2 were associated with improvements in biotic stimuli or defense responses to L. botrana herbivory. Identified changes in the grapevine's transcriptome included those involved in defense signaling of herbivore attack and were associated with the production of reactive oxygen species and phytohormones (such as ethylene, jasmonate and salicylic acid stress hormones), as well as disease resistance proteins, which combination of factors play a critical role in conferring resistance against L. botrana attack.

In light of these encouraging findings, it should come as no surprise that Reineke and Selim conclude by saying their study "indicates that future elevated CO2 concentrations will affect interactions between grapevine plants and one of its key insect pests, with consequences for future relevance of L. botrana in worldwide viticulture." And, gratefully, that relevance will likely be greatly diminished, leading to more robust growth and grape harvests in the years and decades to come as the air's CO2 concentration continues to rise.