Molecular recognition of emerald ash borer infestation using leaf spray mass spectrometry

Leaf Spray Mass Spectrometry: A Rapid Ambient Ionization Technique to Directly Assess Metabolites from Plant Tissues

Plants produce thousands of small molecules that are diverse in their chemical properties. Mass spectrometry (MS) is a powerful technique for analyzing plant metabolites because it provides molecular weights with high sensitivity and specificity. Leaf spray MS is an ambient ionization technique where plant tissue is used for direct chemical analysis via electrospray, eliminating chromatography from the process. This approach to sampling metabolites allows for a wide range of chemical classes to be detected simultaneously from intact plant tissues, minimizing the amount of sample preparation needed. When used with a high-resolution, accurate mass MS, leaf spray MS facilitates the rapid detection of metabolites of interest. It is also possible to collect tandem mass fragmentation data with this technique to facilitate a compound identification. The combination of accurate mass measurements and fragmentation is beneficial in confirming compound identities. The leaf spray MS technique requires only minor modifications to a nanospray ionization source and is a useful tool to further expand the capabilities of a mass spectrometer. Here, fresh leaf tissue from Sceletium tortuosum (Aizoaceae), a traditional medicinal plant from South Africa, is analyzed; numerous mesembrine alkaloids are detected with leaf spray MS.

Liquid chromatography/mass spectrometry for the detection of ash tree metabolites following Emerald Ash Borer infestation

RATIONALE

The Emerald Ash Borer (EAB), Agrilus planipennis, an invasive insect detected in the USA and Canada in 2002, is a threat to ash trees with both ecological and economic implications. Early detection of EAB-infestation is difficult due to lack of visible signs and symptoms in the early stages of attack, but is essential to prevent ash mortality. An efficient and reliable tool for the early detection of EAB-infestation would be advantageous.

METHODS

A mass spectrometry based metabolomics approach, using liquid chromatography/mass spectrometry (LC/MS), has been used to investigate the leaf metabolites of both healthy and EAB-infested trees.

RESULTS

Leaves from 40 healthy and 40 EAB-infested trees were extracted and analyzed using LC/MS. Resulting data were examined to differentiate between foliage from healthy and EAB-infested trees. Possible biomarkers of EAB attack have been detected. Twenty-one metabolites with increased average ion intensity in EAB-infested ash tree samples and nine metabolites with increased average ion intensity in healthy ash tree samples were identified.

CONCLUSIONS

Results of this study indicate that metabolomic screening of leaf samples using LC/MS can be useful as a potential tool for the early detection of EAB-infestation.

Direct detection of surface localized specialized metabolites from Glycyrrhiza lepidota (American licorice) by leaf spray mass spectrometry

Leaf spray-MS minimizes tissue manipulation by effectively and quickly assessing in vivo specialized metabolites from intact plant tissue surfaces, including trichome metabolites. Intact leaves of Glycyrrhiza lepidota Pursh. (American licorice) were analyzed by direct electrospray leaf spray-MS, an ambient ionization technique. Comparison of metabolites detected by leaf spray-MS to those from LC-MS of bulk tissue and trichome enriched extracts showed dramatic differences. Leaf spray-MS results suggest that in specific situations this approach could complement traditional LC-MS analysis of bulk extracts. Leaf spray-MS as a metabolomics technique eliminates sample pretreatment and preparation allowing for rapid sampling in real time of living intact tissues. Specialized metabolites on the surface of tissues such as glandular trichomes metabolites are detected by leaf spray-MS.