Abstract
Green leaf volatiles (GLVs), the common constituents of herbivore-infested plant volatiles (HIPVs), play an important role in plant defense and function as chemical cues to communicate with other individuals in nature. Reportedly, in addition to endogenous GLVs, the absorbance of airborne GLVs emitted by infested neighboring plants also play a major role in plant defense. For example, the exclusive accumulation of (Z)-3-hexenyl vicianoside in the HIPV-exposed tomato plants occurs by the glycosylation of airborne (Z)-3-hexenol (Z3HOL); however, it is unclear how plants process the other absorbed GLVs. This study demonstrates that tomato plants dominantly accumulated GLV–glycosides after exposure to green leaf alcohols [Z3HOL, (E)-2-hexenol, and n-hexanol] using non-targeted LC–MS analysis. Three types of green leaf alcohols were independently glycosylated without isomerization or saturation/desaturation. Airborne green leaf aldehydes and esters were also glycosylated, probably through converting aldehydes and esters into alcohols. Further, we validated these findings in Arabidopsis mutants- (Z)-3-hexenal (Z3HAL) reductase (chr) mutant that inhibits the conversion of Z3HAL to Z3HOL and the acetyl-CoA:(Z)-3-hexen-1-ol acetyltransferase (chat) mutant that impairs the conversion of Z3HOL to (Z)-3-hexenyl acetate. Exposure of the chr and chat mutants to Z3HAL accumulated lower and higher amounts of glycosides than their corresponding wild types (Col-0 and Ler), respectively. These findings suggest that plants process the exogenous GLVs by the reductase(s) and the esterase(s), and a part of the processed GLVs contribute to glycoside accumulation. Overall, the study provides insights into the understanding of the communication of the plants within their ecosystem, which could help develop strategies to protect the crops and maintain a balanced ecosystem.
Highlights
Plant-derived volatile organic compounds play an important role in the interactions between volatile-emitting plants and herbivores, microorganisms, neighboring plants, and different parts of the damaged plants (Arimura et al, 2009)
Metabolite profiles of tomato leaf extracts were compared with LC-MS when the plants were exposed to the structurally different green leaf alcohols, Z3HOL, (E)-2-hexenol (E2HOL), and n-hexanol
In Z3HOL-exposed samples, nine ions of the nineteen candidates were reproducibly detected by LC-HRMS (Supplementary Data 4, green colors) and four ions of nine reproduced ones were statistically different from the control-exposed samples (Supplementary Data 4, dark green color)
Summary
Plant-derived volatile organic compounds play an important role in the interactions between volatile-emitting plants and herbivores, microorganisms, neighboring plants, and different parts of the damaged plants (Arimura et al, 2009). They have three functional groups, aldehyde, alcohol, and esters. Some of the GLVs endogenously produced in the leaf tissues accumulate as glycosides, for example, (Z)-3-hexenyl primeveroside (Z3HexPri) in the tea leaves (Ohgami et al, 2015; Jing et al, 2019) As evident from these studies, the biosynthetic pathways of endogenous GLVs have been extensively explored; little is known about how exogenous airborne GLVs are processed in plants. The findings of this study could be helpful in the understanding of the communication of the plants within their ecosystem and, could assist in developing strategies to protect the crops and the natural flora, and maintain a balanced ecosystem
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