A Reservoir of Pluripotent Phloem Cells Safeguards the Linear Developmental Trajectory of Protophloem Sieve Elements
38 Pages Posted: 9 Sep 2019 Sneak Peek Status: Review CompleteMore...
Plant cells can change their identity based on positional information, a mechanism that confers developmental plasticity to plants. This ability, common to distinct multicellular organisms, is particularly relevant for plant phloem cells. Protophloem sieve elements (PSEs), one type of phloem conductive cells, act as the main organizers of the phloem pole, which comprises four distinct cell types organized in a conserved pattern. Here, we report how Arabidopsis roots generate a reservoir of uncommitted phloem cells competent to swap their cell identities. While PSE misspecification induces cell identity hybridism, the activity of RECEPTOR LIKE PROTEIN KINASE 2 (RPK2) by perceiving CLE45 peptide contributes to restrict PSE identity to the PSE position. By maintaining a spatio-temporal window when PSE and PSE-adjacent cells’ identities are interchangeable, CLE45 signaling endows phloem cells with the competence to re-pattern a functional phloem pole when protophloem fails to form.
Keywords: cell identity, phloem, companion cell, plastic developmental trajectory, RPK2, CLE peptides
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