Phospho-proteomic analysis of developmental reprogramming in the moss Physcomitrella patens

One of the most common post-translational modifications is protein phosphorylation, which controls many activities of plant life. However, its role in the reprogramming of developmental pathways of plant cells remains elusive. Here, using Physcomitrella patens, we characterize the phospho-proteome for protonemata, protoplasts made therefrom, and protoplasts regenerated for 2d. Through a titanium dioxide (TiO2)-based phospho-peptide enrichment method and liquid chromatography-tandem mass spectrometry (LC-MS/MS), more than 2000 phospho-proteins were identified. Among the 519 proteins with functional annotation in fresh protoplasts and protoplasts regenerated for 2d, proteins involved in epigenetic modification, post-transcriptional gene regulation, hormone signal transduction, and meristem maintenance have been previously reported to be important for developmental reprogramming. Several novel transcription factors including SWI/SNF complex protein, SNF2 family protein and MADS-domain transcription factor appear to be important in developmental reprogramming plant cells. Phosphorylation of marker proteins such as somatic embryogenesis receptor kinase and NAC transcription factor, suggests that this post-translational modification is vital for the cell's ability to adjust its developmental program. Together, our study presents a more complete understanding of the plant cell's developmental reprogramming.

Protoplast regeneration is an ideal model system for investigating developmental reprogramming in plants. Here, for Physcomitrella patens, we characterize the phospho-proteome for protonemata, protoplasts made therefrom, and for protonemata regenerated from the protoplasts for 2d. Among the 519 proteins with functional annotation in fresh protoplasts and protoplasts regenerated for 2d, proteins involved in epigenetic modification, post-transcriptional gene regulation, hormone signal transduction, and meristem maintenance have been reported to be important for expression of developmental reprogramming. Together, our study presents a more complete understanding of the plant cell's developmental reprogramming.