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BACKGROUND: Grapevine red blotch virus (GRBV) is the causal agent of grapevine red blotch disease and is known to delay grape ripening. However, grape cell‐wall modifications during GRBV infection are largely unknown, even though the cell wall plays a large role in pathogenicity, viral interactions with host plants, and phenolic extractability during winemaking. Understanding the impact of GRBV infection on cell‐wall metabolism is important for the development of potential mitigations strategies. In this study, high‐throughput transcriptome sequencing was conducted on Vitis vinifera L. 'Merlot' grapes during ripening. The cell‐wall composition, phenolic content, and phenolic extractability at two different commercial harvest points were also determined. RESULTS: Log fold changes indicated a strong induction in diseased grapes at harvest of several transcripts involved in cell‐wall solubilization and degradation. However, these observations did not translate to changes in cell‐wall composition at either harvest point in diseased grapes, potentially suggesting post‐transcriptional regulation. Moderate induction of pectin methylesterase inhibitor transcripts and transcripts associated with pathogenesis‐related proteins coincided with increases in pectin and soluble proteins in cell walls of diseased grapes at harvest. Both pectin and pathogenesis‐related proteins are known to retain phenolic compounds during winemaking. CONCLUSION: Our study corroborates this finding when the percentage extractability of flavonols in wines was significantly lower when made from GRBV‐infected fruit. These results suggest GRBV alters the grape cell walls, consequently decreasing phenolic extraction during winemaking. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

A novel cucumber mosaic virus inducible viral amplicon (CMViva) expression system has been developed that allows for tightly regulated chemically inducible expression of heterologous genes in plant hosts. Transient production of recombinant α1-antitrypsin (rAAT), a human blood protein, was demonstrated in Nicotiana benthamiana leaves. The highest production levels were obtained by co-infiltrating leaves with Agrobacterium tumefaciens cells containing CMViva carrying the AAT gene and A. tumefaciens cells carrying a binary vector constitutively expressing the gene silencing suppressor p19. Accumulation of up to thirty-fold more rAAT was observed in leaves (24 mg per 100 g leaf tissue) when compared with the expression levels observed using the cauliflower mosaic virus (CaMV) 35S promoter. Significantly, 70% of the rAAT produced using the CMViva expression system was found to be biologically active, a 170-fold increase in functional protein compared with the CaMV 35S expression system. [ABSTRACT FROM AUTHOR]