Expression pattern of ERL1pro::ERL1-YFP. (A–J) Time-lapse live imaging of developing abaxial cotyledon epidermis of the 1-day-old T4 seedling of ERL1pro::ERL1-YFP erl1-2. Time points after image collection are indicated in hours:(A) 0.0 hr; (B) 3.5 hr; (C) 13.0 hr; (D) 16.0 hr; (E) 24.5 hr; (F) 26.0 hr; (G) 36.0 hr; (H) 50.5 hr; (I) 68.0 hr; and (J) 71.0 hr. Arrowheads point to two representative cells. Images for (A–J) are taken at the same magnification. Scale bar, 10 µm. (K–L) High resolution live images of stomatal precursors expressing ERL1-YFP. (K, L) meristemoid mother cells (MMC); (M) meristemoid (M); (N) late meristemoid (late M); (O) late meristemoid to guard mother cell transition (late M~GMC); (P) GMC; (Q) immature guard cells (im GC). Images for (K–L) are taken at the same magnification. Scale bar, 7.5 µm. ERL1-YFP signals are detected at the plasma membrane from early meristemoids (A, K, L; arrowheads) and accumulate high at the asymmetric division site (e.g. D, F, M; cyan asterisks). ERL1-YFP signals boost during the late meristemoid-to-GMC transition (G, H, N, O; cyan plus), and diminishes after GMC symmetric division (I, J, P, Q; arrowheads). See accompanying Video 1. Experiments were repeated three times. Total seedlings analyzed; n = 9.
Autocrine regulation of stomatal differentiation potential by EPF1 and ERECTA-LIKE1 ligand-receptor signaling
Qi X., Han S.-K., Dang J. H., Garrick J. M., Ito M., Hofstetter A. K., Torii K. U. (2017)
Xingyun Qi, Soon-Ki Han, Jonathan H. Dang, Jacqueline M. Garrick, Masaki Ito, Alex K. Hofstetter, Keiko U. Torii,
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In Plant Biology, Developmental Biology – https://doi.org/10.7554/eLife.24102.001 –
https://elifesciences.org/articles/24102
Shown are confocal microscopy images of cotyledon abaxial epidermis from 7-day-old seedlings of the following genotypes: (A) er erl1 erl2; (B) MUTEpro::ERL1-YFP in er erl1 erl2; (D) er erl1 erl2 epf1 epf2; (E) MUTEpro::ERL1-YFP in er erl1 erl2 epf1 epf2; (F) MUTEpro::ERL1-YFP in er erl1 erl2 mock treated; (G) MUTEpro::ERL1-YFP in er erl1 erl2 treated with 5 µM Stomagen peptide; (H) er erl1 erl2 tmm; (I) MUTEpro::ERL1-YFP in er erl1 erl2 tmm. T1 transgenic seedlings of MUTEpro::ERL1-YFP er erl1 erl2; MUTEpro::ERL1-YFP er erl1 erl2 epf1 epf2; and MUTEpro::ERL1-YFP er erl1 erl2 tmm were used for the analysis. T2 seedlings of MUTEpro::ERL1-YFP er erl1 erl2 were used for the mock or Stomagen treatment. Scale bars, 10 µm (A, B, D, E, H, I), 25 µm (F, G). (C) Quantitative analysis. Stomatal index (SI) of the cotyledon abaxial epidermis from 7-day-old seedlings of respective genotypes. For each genotype, images from six seedlings were analyzed. Welch’s Two Sample T-test was performed for mock vs. Stomagen application (Left). One-way ANOVA followed by Tukey’s HSD test was performed for comparing all other genotypes and classify their phenotypes into three categories (a, b, and c).
Abstract
Development of stomata, valves on the plant epidermis for optimal gas exchange and water control, is fine-tuned by multiple signaling peptides with unique, overlapping, or antagonistic activities. EPIDERMAL PATTERNING FACTOR1 (EPF1) is a founding member of the secreted peptide ligands enforcing stomatal patterning. Yet, its exact role remains unclear. Here, we report that EPF1 and its primary receptor ERECTA-LIKE1 (ERL1) target MUTE, a transcription factor specifying the proliferation-to-differentiation switch within the stomatal cell lineages. In turn, MUTE directly induces ERL1. The absolute co-expression of ERL1 and MUTE, with the co-presence of EPF1, triggers autocrine inhibition of stomatal fate. During normal stomatal development, this autocrine inhibition prevents extra symmetric divisions of stomatal precursors likely owing to excessive MUTE activity. Our study reveals the unexpected role of self-inhibition as a mechanism for ensuring proper stomatal development and suggests an intricate signal buffering mechanism underlying plant tissue patterning.
PLANT STOMATA ENCYCLOPEDIA 
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