Phoebe bournei is a precious timber species unique to China, possessing significant ornamental, ecological, and medicinal values. The polyembryonic phenomenon is widely observed in its seeds, but the underlying mechanisms driving its formation remain unclear. In this study, an integrated analysis was conducted for polyembryony formation in P. bournei seeds, including biochemical indicators, environmental factors, and transcriptional levels. Firstly, morphological observation of seeds from 13 plus trees showed no significant correlation between polyembryony rate and external environment or seed morphology. Subsequently, comparative transcriptomic analysis between monoembryonic and polyembryonic seeds identified 1957 differentially expressed genes (DEGs), which were significantly enriched in biological processes and pathways including photosystem II, tetrapyrrole binding, heme binding, and phenylpropanoid biosynthesis, indicating the probable effect of gene regulation in polyembryony formation. Furthermore, eight RWP transcription factors were identified, potentially involved in polyembryony. qRT-PCR analysis revealed that the expression levels of PbRWP2 and PbRWP5 were significantly upregulated in polyembryonic seeds, indicating they may be key regulatory genes during polyembryony formation in P. bournei seeds. This study preliminarily explored the transcriptomic characterization and potential molecular regulatory basis of polyembryony formation in P. bournei, laying a critical foundation for further deciphering the intricate mechanisms governing its polyembryonic development.

Phoebe bournei is an economically and ecologically important woody species native to China. As a core component of colchicine-triggered polyploid breeding, the tubulin genes (TUA and TUB) have been identified and functionally analyzed in many plants, but not yet in P. bournei. Here, tubulin family members in P. bournei were identified through sequence alignment and subsequently characterized using comprehensive bioinformatic analyses. In particular, a total of six PbTUA and ten PbTUB members were identified and grouped into two and five subfamilies, respectively, according to phylogenetic relationships. Most tubulin proteins were small (414–522 aa) with predicted stability. Furthermore, 36 collinear gene pairs were identified, suggesting a possible contribution to the evolutionary expansion of this family. For different tissues, the expression levels of most tubulin genes were generally lower in leaves but higher in roots. Besides, treatment with 1.0% colchicine inhibited the expression of all 15 tubulin genes except PbTUB6. These results provide preliminary insights into tubulin genes associated with polyploid induction and supply candidate genes for future functional studies toward polyploid germplasm creation of P. bournei.