Assessing Bioactivity of Green Leaf Volatiles in Various Plant Systems

Green leaf volatiles (GLVs) are chemical compounds essential in plant communication. Plants emit these volatiles due to abiotic and biotic stressors and, when perceived, these GLVs activate defense responses. Though GLVs play an important role in plant survival, it is still unknown where they localize, how they are perceived, and what structural factors influence perception. To elucidate these structural determinants, we tested the bioactivity of (Z)-3-fatty alcohols with four to nine carbons. Through root growth inhibition assays with tomato (Solanum peruvianum) seedlings, we found that (Z)-3-octenol and (Z)-3-nonenol were more bioactive than (Z)-3 hexenol and (Z)-3-heptenol. Thus, higher bioactivity was seen among the longer chain lengths. The exception was (Z)-3-butenol, which had a higher bioactivity than (Z)-3-hexenol. To determine intracellular signaling events upon GLV perception, we tested for the phosphorylation of MAP kinases (MAPKs) in Arabidopsis (Arabidopsis thaliana). We found that both HOL and HAC induce MAPK3/6 phosphorylation in different application systems with seedlings. We also wanted to determine if adding an azide mini tag onto the GLV (Z)-3-hexenyl acetate would impact the bioactivity. In Solanum peruvianum suspension-cultured cells, we found that both the (Z)-3-hexenyl acetate and the mini-tagged derivative induce medium acidification. However, in Arabidopsis seedlings, we found that only (Z)-3-hexenyl acetate induced a MAP kinase phosphorylation response. We also tested the bioactivity of azide-tagged GLV derivatives with six to nine carbons to explore how the carbon chain length influences bioactivity. We found that the longer the carbon chain, the lower the medium acidification response. Thus, there is a reverse relationship between bioactivity and chain length for mini-tagged (Z)-3-hexenyl acetate derivatives.