The laccase gene CcLac2 is essential for the summer-form to winter-form transition in the Chinese pear psyllid.

BACKGROUND: The Chinese pear psyllid (Cacopsylla chinensis), a vector of the bacterial pathogen Erwinia amylovora, displays seasonal polyohenism, transitioning from a summer-form to a winter-form in response to temperature fluctuations. Although the winter-form phenotypes, characterized by enhanced cuticular melanization and thickening, have been extensively documented, the underlying molecular regulatory network remains poorly understood. Given the pivotal biological functions of laccases in insect cuticular melanization and sclerotization, in this research, we systematically investigated the molecular characteristics of the laccase genes CcLac1 and CcLac2, as well as their regulatory roles in driving this seasonal polyphenism. RESULTS: Our results showed that CcLac2 was predominantly expressed in the epidermis and markedly upregulated under low-temperature conditions. Functional investigations using RNA interference (RNAi) further revealed that CcLac2 plays an essential role in promoting the transition from the summer- to winter-form by orchestrating cuticular pigment deposition, cuticle thickening, and chitin deposition. In contrast, CcLac1 was not significantly involved in low-temperature mediated morphological alterations. CONCLUSION: In summary, this study provides solid experimental evidence confirming that CcLac2 is critical for seasonal morph transition in C. chinensis, advancing our understanding of the molecular mechanisms underlying arthropod seasonal adaptation and identifying potential molecular targets for precision-based management strategies for this economically important pest. © 2026 Society of Chemical Industry.