AUTHOR=Caarls Lotte , Bassetti Niccolò , Verbaarschot Patrick , Mumm Roland , van Loon Joop J. A. , Schranz M. Eric , Fatouros Nina E. 

TITLE=Hypersensitive-like response in Brassica plants is specifically induced by molecules from egg-associated secretions of cabbage white butterflies

JOURNAL=Frontiers in Ecology and Evolution

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2022.1070859

DOI=10.3389/fevo.2022.1070859

ISSN=2296-701X

ABSTRACT=<p>Plants perceive and respond to herbivore insect eggs. Upon egg deposition on leaves, a strong hypersensitive response (HR)-like cell death can be activated leading to egg desiccation and/or dropping. In <italic>Brassica</italic> spp., including many crops, the HR-like mechanism against eggs of cabbage white butterflies (<italic>Pieris</italic> spp.) is poorly understood. Using two <italic>Brassica</italic> species, the crop <italic>B. rapa</italic> and its wild relative <italic>B. nigra</italic>, we studied the cellular and molecular plant response to <italic>Pieris brassicae</italic> eggs and characterized potential insect egg-associated molecular patterns (EAMPs) inducing HR-like cell death. We found that eggs of <italic>P. brassicae</italic> induced typical hallmarks of early immune responses, such as callose deposition, production of reactive oxygen species and cell death in <italic>B. nigra</italic> and <italic>B. rapa</italic> leaf tissue, also in plants that did not express HR-like cell death. However, elevated levels of ethylene production and upregulation of salicylic acid-responsive genes were only detected in a <italic>B. nigra</italic> accession expressing HR-like cell death. Eggs and egg wash from <italic>P. brassicae</italic> contains compounds that induced such responses, but the eggs of the generalist moth <italic>Mamestra brassicae</italic> did not. Furthermore, wash made from hatched <italic>Pieris</italic> eggs, egg glue, and accessory reproductive glands (ARG) that produce this glue, induced HR-like cell death, whereas washes from unfertilized eggs dissected from the ovaries or removal of the glue from eggs resulted in no or a reduced response. This suggests that there is one or multiple egg associated molecular pattern (EAMP) located in the egg glue a that teresponse in <italic>B. nigra</italic> is specific to <italic>Pieris</italic> species. Lastly, our results indicate that the EAMP is neither lipidic nor proteinaceous. Our study expands the knowledge on the mechanism of <italic>Brassica</italic>-<italic>Pieris</italic>-egg interaction and is a step closer toward identification of EAMPs in <italic>Pieris</italic> egg glue and corresponding receptor(s) in <italic>Brassica.</italic></p>