CsaHOS1 homeologs regulate seed development and fatty acid accumulation in Camelina sativa under different temperature and photoperiod conditions

Temperature and photoperiod influence plant development and seed lipid accumulation, but the molecular mechanisms underlying these responses in oilseed crops remain incompletely understood. HOS1, a RING-type E3 ubiquitin ligase involved in environmental signaling and developmental regulation, has not been functionally characterized in oilseed crops. Here, we investigated three HOS1 homeologs ( CsaHOS1-A, CsaHOS1-B , and CsaHOS1-C ) in allohexaploid Camelina sativa , an industrial oilseed crop. Sequence and expression analyses revealed conserved protein domains and high transcript accumulation during seed development. CRISPR/Cas9-mediated mutagenesis revealed phenotypic differences consistent with functional redundancy among the three homeologs, with higher-order mutants exhibiting growth defects and abnormal seed morphology. The csahos1-aabbcc triple mutants exhibited approximately 80–90% abnormal seeds, while seed weight and total fatty acid content decreased by up to 22% and 34%, respectively, in higher-order mutants. At 22 °C, the csahos1-aabbcc triple mutant exhibited reduced absolute contents of oleic acid (18:1), linoleic acid (18:2), and α-linolenic acid (18:3) under both long-day and short-day conditions. Elevated temperature (28 °C) was associated with reduced seed weight and fatty acid accumulation in genotypes that produced mature seeds. Notably, the csahos1-aabbcc triple mutant failed to produce mature seeds at 28 °C under both photoperiod conditions. These findings indicate that CsaHOS1 homeologs contribute to seed development and fatty acid accumulation under different environmental conditions, although the underlying molecular mechanisms remain to be elucidated.