Dynamic proteomics reveals that endosperm weakening plays a critical role during seed germination in Polygonatum...

Polygonatum cyrtonema Hua, a valued Chinese medicinal herb, faces challenges in cultivation and seedling quality due to seed dormancy, a combinational type resulting from multiple factors whose molecular mechanisms remain unclear.

This study employed iTRAQ-based proteomics, transcriptomics, and hormone profiling to analyze three key germination stages (S1, pulp removal and initial imbibition. S2, radicle emergence through the seed coat. S3, transition phase between primary root elongation and cotyledon emergence).

Morphological observations indicated gradual endosperm weakening and embryo development during germination. Transcriptomics highlighted 30 enriched pathways, notably plant hormone signaling and starch and sucrose metabolism. Proteomics revealed consistent enrichment of FOG: RRM domain, aspartyl protease, and β-fructofuranosidase across comparisons. Hormone assays showed decreases in ABA, bioactive GAs, IAA, JA, and SA from S1 to S3, with a marked increase in the bioactive GAs/ABA ratio. Integrated omics emphasized metabolism and hormone signal transduction. Key enzymes in starch and sucrose metabolism (e.g., β-fructofuranosidase, α-xylosidase, β-D-xylosidase, and β-glucosidase) increased, supporting energy conversion and endosperm weakening. Conversely, ABA-related proteins (PYL4, PP2C) decreased. Sucrose synthase, involved in ABA-GA antagonism, also declined.

These results underscore synergistic endosperm weakening and hormonal regulation during P. cyrtonema seed germination, offering new insights for improving germination in species constrained by endosperm strength.