For Abstract see ChemInform Abstract in Full Text.

Induction of jasmonate-mediated plant defense against insect herbivory is initiated by a combination of both, mechanical wounding and chemical factors. In order to study both effects independently on plant defense induction, SpitWorm, a computer-controlled device which mimics the damage pattern of feeding insect larvae on leaves and, in addition, can apply oral secretions (OS) or other solutions to the ‘biting site’ during ‘feeding’, was developed and evaluated. The amount of OS left by a Spodoptera littoralis larva during feeding on Phaseolus lunatus (lima bean) leaves was estimated by combining larval foregut volume, biting rate, and quantification of a fluorescent dye injected into the larvae’s foregut prior to feeding. For providing OS amounts by SpitWorm equivalent to larval feeding, dilution and delivery rate were optimized. The effectiveness of SpitWorm was tested by comparing volatile organic compounds (VOC) emissions of P. lunatus leaves treated with either SpitWorm, MecWorm or S. littoralis larvae. Identification and quantification of emitted VOCs revealed that SpitWorm induced a volatile bouquet that is qualitatively and quantitatively similar to herbivory. Additionally, RT-qPCR of four jasmonic acid responsive genes showed that SpitWorm, in contrast to MecWorm, induces the same regulation pattern as insect feeding. Thus, SpitWorm mimics insect herbivory almost identical to real larvae feeding.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Chlorophylls (Chls), the green pigments responsible for photosynthesis in plants, algae and bacteria, are also part of the daily diet of herbivorous feeders. Chl degradation occurs during leaf senescence and fruit ripening but is also noticed as a response to biotic and abiotic stresses. Besides the programmed degradation during senescence different factors such as high temperature, extreme pH values, enzymatic actions, molecular oxygen, and light initiate the degradation of Chl. To gain more information on Chl degradation in the gut of plant-feeding insects, regurgitate and frass of Spodoptera littoralis caterpillars were analysed for late Chl catabolites by using LC-MS, UV, Fluorescence and NMR spectroscopy. The major metabolites were determined in fresh leaves of the food plant lima bean (Phaseoluslunatus), and were compared with digestive products. The observed spectrum of metabolites can be attributed to the combined action of esterolytic gut enzymes and the strongly alkaline milieu in the digestive tract. Interestingly, linear Chl catabolites were not detected in the gut of the larvae of S. littoralis. Substantial amounts of Chl catabolites were found to be macrocyclic rings opened in the senescent food plants, but also in the aged frass. We studied two primary fluorescent chlorophyll catabolites in senescent leaves of lima bean. One of the primary fluorescent chlorophyll catabolites that have been found in the frass of S. littoralis might be generating opened tetrapyrroles of Chl, only after being exposed to the air and light.