Evolutionary divergence of CXE gene family in green plants unveils that PtoCXEs overexpression reduces fungal colonization in transgenic Populus.

This article focuses on the evolutionary diversification and functional characterization of the carboxylesterase (CXE) gene family in Viridiplantae, with an emphasis on Populus species. A total of 784 CXE genes were identified across 31 plant species representing major Viridiplantae lineages and classified into five clades, reflecting their evolutionary origins linked to bacterial ancestry and key plant groups such as bryophytes, ferns, and seed plants. In Populus trichocarpa, 51 CXE genes were found, expanded through tandem and segmental duplications, and grouped into eight classes showing varied gene structures and expression patterns under biotic and abiotic stresses. Functional assays in transgenic Populus tomentosa demonstrated that overexpression of six Class VI CXE genes reduced colonization by the fungal pathogen Cytospora chrysosperma, indicating a role in disease resistance and providing candidate genes for genetic improvement of forest tree resilience.