Outlook: From the cell culture to the vineyard – routes
towards application.
The induction of oxidative burst (Figure 7C ), transcripts for
MYB14 and RS (Figure 7A ), and accumulation of the bioactive
phytoalexin, trans -resveratrol (Figure 7B ) by
Al3+ in leaf discs of grapevine indicates that the
signalling chain discussed above is active not only in suspension cells
but in planta as well. Even genotype-dependent differences in the
response amplitude between the more responsive sylvestrisgenotype Hö29 and the less responsive vinifera genotype Augster
Weiss seen in earlier studies (Duan et al. , 2015; 2016) are
preserved. The differences seen on the level of phytoalexins synthesis
transcripts (RS ) or the specific transcription factor triggering
these genes (MYB14 ) are preceded by corresponding differences in
the abundance of MDA. This indicates that the differential response of
the two genotypes, which is also seen for UVC or the Oomycete pathogenPlasmopara viticola (Duan et al. , 2015) is caused far
upstream, possibly at the abundance or activation of RboH. Our findings
also opens a new interpretation for the mode of action of Al-based
compounds acting against Oomycete pathogens (Dercks & Buchenauer,
1987). Rather than acting through interfering with the pathogen itself,
such compounds might act to stimulate or prime the immunity of the host.
Especially for P. viticola, the causative agent of Downy Mildew of
Grapevine, this would open new avenues for plant protection. Rather than
the need to rely on the very short time window, where the infecting
zoospore still has not entered the stoma (leading to the excessive
fungicide load characteristic for viticulture), a prophylactic treatment
would be feasible, where the host, rather the pathogen is addressed.