Transcriptomic Analysis and Physiological Indicators Synthetically Uncover Candidate Genes Regulating Polyembryony Formation of Phoebe bournei Seeds

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.