Chlorophyll Degradation in the Gut of Generalist and Specialist Lepidopteran Caterpillars

Abstract

Plant feeding herbivores excrete most of the ingested chlorophyll (Chl) as partly degraded derivatives lacking the phytol side chain and the central magnesium ion. An ecological role of digested and degraded Chls in the interactions between insects, their food plant and other insects has been described recently. To gain more information on common degradation patterns in plant-feeding insects, the orals secretions and frass of five Lepidopteran caterpillars covering generalists and specialists, namely Spodoptera littoralis, Spodoptera eridania, Heliothis virescens, Helicoverpa armigera, Manduca sexta, and, for comparison, of the leaf beetle larva Chrysomela lapponica were analyzed for chlorophyll catabolites. The major degradation products were determined as pheohorbide a/b and pyropheophorbide a/b by using LC-MS, LC-NMR, UV, and fluorescence spectrometry. The compounds were not present in fresh leaves of the food plants (Phaseolus lunatus, Nicotiana tabacum). The catabolite spectrum in generalists and specialists was qualitatively similar and could be attributed to the action of gut proteins and the strongly alkaline milieu in the digestive tract. Due to the anaerobic environment of the larval gut, the tetrapyrrole core of the Chl catabolites was not cleaved. Substantial amounts of Chl a/b metabolites were strongly complexed by a protein in the mid-gut.

Breakdown of Chlorophyll in Higher Plants—Phyllobilins as Abundant, Yet Hardly Visible Signs of Ripening, Senescence, and Cell Death

“…In a distantly related context, exploratory studies of Chl breakdown in herbivorous protists and insects were recently reported. Thus, in the gut and digestive tract of herbivorous caterpillars, Pheo a was detected as the major left‐over product of the ingested Chl . Furthermore, in the aquatic ecosystem, herbivorous protists were found to degrade (and detoxify) ingested Chl to a nonfluorescent cyclopheophorbide a enol .…”

Reexamination of Chlorophyllase Function Implies Its Involvement in Defense against Chewing Herbivores

“…Because chlorophyll hydrolysis is known to occur commonly in the gut of insect herbivores (Park et al, 2003;Badgaa et al, 2014), it is plausible that CLH continues to produce chlorophyllide as the ingested leaf tissue passes through the insect guts.…”

Der Chlorophyllabbau in höheren Pflanzen – Phyllobiline als weitverbreitete, aber kaum sichtbare Zeichen von Reifung, Seneszenz und Zelltod

“…Entfernt verwandte neuere Studien beschäftigten sich mit der Frage des Chl‐Abbaus in pflanzenfressenden Protisten und Insekten. Im Darm und Verdauungstrakt von herbivoren Raupen wurde Pheo a als dominantes Überbleibsel des aufgenommenen Chl detektiert . Im aquatischen Ökosystem bauen (und entgiften) pflanzenfressende Protisten mit der Nahrung aufgenommenes Chl zu einem außergewöhnlichen Chl‐Abkömmling ab, dem nichtfluoreszierenden Cyclophäophorbid‐ a ‐Enol .…”