Wounded strawberry fruit produces a diverse group of volatile compounds including
aldehydes,
alcohols, and
esters derived from the
lipoxygenase (LOX) and
hydroperoxide lyase (HPL) pathways. Because the
wound volatiles may play an important role in plant-fungal interaction, the goal of this study was to develop a greater understanding about the biosynthesis of the major
wound volatile,
trans-2-hexenal (t-2-H), produced by strawberry fruit upon wounding. To that end, composition and quantity of total and
free fatty acids of control and wounded strawberry fruit were analyzed. In addition, activities of the key
enzymes, LOX and HPL, and production of C6
aldehydes were determined. Intact strawberry fruit did not produce detectable t-2-H which is derived from
alpha-linolenic acid (18:3). However, in response to wounding by bruising, strawberry fruit emitted t-2-H and its precursor cis-3-hexenal (c-3-H). The level of total
lipid 18:3 in the fruit increased 2-fold in response to wounding, whereas free 18:3 declined slightly ( approximately 30%).
At 10 min following wounding, fruit exhibited a 25% increase in LOX activity, which leads to the production of 13-hydroperoxyoctadecatrienoic
acid (13-HPOT) from 18:3. The activity of HPL, which catalyzes formation of cis-3-hexenal from
13-HPOT, increased 2-fold by 10 min after wounding. Thus, during a 15 min period after wounding, free 18:3 substrate availability and the activity of two key
enzymes, LOX and HPL, changed in a manner consistent with increased c-3-H and t-2-H biosynthesis.