Botrytis cinerea activates virulence-related metabolism in the
interaction with tolerant green grapes
Abstract
Botrytis cinerea is responsible for the gray mold disease,
severely affecting Vitis vinifera grapevine and hundreds of other
economically important crops. However, many mechanisms of this
fruit-pathogen interaction remain unknown. The combined analysis of the
transcriptome and metabolome of green fruits infected with B.
cinerea from susceptible and tolerant genotypes was never performed in
any fleshy fruit, mostly because green fruits are widely accepted to be
resistant to this fungus. In this work, peppercorn-sized fruits were
infected in the field or mock-treated, and infected berries were
collected at green (EL32) stage from a susceptible (Trincadeira) and a
tolerant (Syrah) variety. RNAseq and GC-MS data suggested that Syrah
exhibited a pre-activated/basal defense relying on specific signaling
pathways, hormonal regulation, specifically jasmonate and ethylene
metabolism, and linked to phenylpropanoid metabolism. In addition,
putative defensive metabolites such as shikimic, ursolic/ oleanolic, and
trans-4-hydroxy cinnamic acids, and epigallocatechin were more
abundant in Syrah than Trincadeira before infection. On the other hand,
Trincadeira underwent relevant metabolic reprogramming upon infection
but was unable to contain disease progression. RNA-seq analysis of the
fungus in planta revealed an opposite scenario with higher gene
expression activity within B. cinerea during infection of the
tolerant cultivar and less activity in infected Trincadeira berries. The
results suggested an activated virulence state during interaction with
the tolerant cultivar without visible disease symptoms. Together, this
study brings novel insights related to early infection strategies of
B. cinerea and the green berry defense against necrotrophic
fungi.