Another new observation is that lower transcript abundance
was found between thiamine-treated and control plants for a thionin
gene sequence. This gene was further down-regulated after
aphid infestation. Thionins are sulphur-rich proteins which mostly
have been associated with defence functions against pathogens
(Bohlmann and Apel, 1991). We have no explanation to the expression
pattern of the thionin gene found upon thiamine treatment or aphid infestation. All results concerning gene expression are correlative and further studies are needed to find out whether they are related to the effects on aphid reproduction and behaviour. As yet, no resistance factor towards R. padi has been identified in
barley.