MaEIN2 links ethylene signaling to chlorogenic acid accumulation in mulberry leaves in response to silkworm-feeding

Mulberry ( Morus alba L) leaves are the sole food source of the domesticated silkworm ( Bombyx mori ) and are rich in chlorogenic acid (ChA), a phenolic metabolite implicated in plant defense and silkworm performance. However, how herbivory-associated cues are integrated with ethylene (ET) signaling to regulate ChA accumulation remains elusive. Here, we found that silkworm feeding markedly enhanced ChA levels in mulberry leaves, accompanied by notable cascading changes in genes associated with the ethylene (ET) signaling pathway, particularly Morus alba L. ETHYLENE INSENSITIVE 2 ( MaEIN2 ), indicating that ET is involved in the stress response elicited by silkworm feeding. Virus-induced gene silencing (VIGS) of MaEIN2 significantly reduced ChA accumulation and downregulated downstream genes implicated in ChA biosynthesis. Moreover, MaEIN2 -silenced seedlings exhibited compromised resistance to A. tumefaciens harboring tobacco rattle virus (TRV)-based plasmids, supporting a role for MaEIN2 in biotic stress defense. Collectively, these results indicate that MaEIN2 mediates ET-dependent defense responses by modulating ChA accumulation in mulberry. Furthermore, herbivory-induced stress appears to operate through MaEIN2 -dependent ET signaling, which elevates ChA content potentially to accommodate silkworm developmental needs. This study provides new insights into the role of MaEIN2 in linking silkworm feeding with ChA accumulation in mulberry.