Francisco Augusto Santos de Azevedo Carioca¹, Yara Martins da Silva², Victor Mateus Barroso Lopes Morais¹, Jonatas de Freitas Oliveira¹, Fábio César Souza Nogueira², Gilberto Barbosa Domont², Francisco de Assis de Paiva Campos¹

The carnauba palm (Copernicia prunifera), a native species of Brazil’s semi-arid Northeast and a member of the Arecaceae family, is culturally emblematic and economically vital due to its multipurpose products such as wax, oil, and fibers. Despite its importance, Arecaceae seeds are known for their dormancy and slow germination, and the molecular mechanisms underlying these processes remain poorly understood. To address this gap, we investigated the dynamic changes in the proteome and phosphoproteome of C. prunifera seeds during imbibition—the critical water uptake phase that precedes germination. Proteins were extracted from seeds at four key developmental stages (mature, 4DAI, 7DAI, and germinated), followed by label-free quantification using high-resolution mass spectrometry. A total of 4,431 proteins were identified, from which 924 proteins were enriched using titanium dioxide. From this pool, 385 were confirmed as phosphorylated, yielding an enrichment efficiency of 41.7%. These phosphoproteins increased in number from 199 (mature) to 331 (germinated), reflecting enhanced signaling activity during germination. Functional categorization showed enrichment of kinases, splicing factors, multifunctional proteins, and epigenetic regulators among phosphoproteins, whereas categories such as redox metabolism, amino acid metabolism, proteases, and secondary metabolism were depleted. Quantitative analysis revealed 1,159 differentially abundant proteins across stages, with 532 upregulated and 627 downregulated. Among the phosphoproteins, 23 phosphopeptides from 21 proteins showed significant changes, including motifs associated with acidophilic and proline-directed kinases, particularly casein kinase II (CK2). Of 617 total phosphorylation sites, serine phosphorylation was predominant (~93%), followed by threonine and minimal tyrosine phosphorylation. Motif analysis identified 45 significantly enriched patterns, highlighting conserved phosphorylation signatures across monocots. This study provides the first large-scale proteomic and phosphoproteomic landscape of C. prunifera seeds during germination. It identifies key regulatory proteins and phosphorylation events critical for seed activation, offering new insights into palm seed biology and potential molecular targets to improve germination efficiency and conservation strategies for Arecaceae species.

Agradecimentos: Financial support from CAPES and CNPq are gratefully acknowledged.