Fig. 2: Synergids are glandular cells generating many peptides via a ZmMYB98 controlled GRN.
From: Fertilization-induced synergid cell death by RALF12-triggered ROS production and ethylene signaling
a Proportion comparison of the 30 most highly expressed genes in synergid cells before pollination. 86.7% genes encode proteins containing predicted signal sequences for targeting to the secretory pathway. Egg cells and zygotes at 24 HAP are included for comparison. b Subcellular distribution of most abundant gene products in indicated cells. Localization of the fusion proteins SC1-GFP (a CRP) (c) and SC3-GFP (a PMEI) (d) in synergid cells and cell walls of micropylar nucellus cells in mature embryo sacs before pollination. Arrowheads point towards extracellular signals at the micropylar nucellus region. e Heatmap showing expression pattern of the TOP200 synergid cell-expressed genes during progression of synergid degeneration. f Expression analysis of the most abundant synergid cell-expressed transcription factors during synergid degeneration. For statistical analysis, count data at the gene level were analyzed with DESeq264. Stage-to-stage comparisons were performed and corrected for multiple testing over all genes and cell stage comparisons using false discovery rate (FDR). Letters indicate significant differences between developmental stages (adjusted P < 0.05). g Scheme of reporter and effector vectors for dual-luciferase transactivation assays presented in (h). h Transactivation assay showing that ZmMYB98 positively regulates a comprehensive set of most highly expressed synergid-specific/predominant genes. Data from previous publications22,69,70 were used to identify synergid-specific/predominant genes (Supplementary Data 4 and 6). Relative ratio of firefly luciferase (LUC) to Renilla luciferase (REN) was used to determine relative promoter activation activity. Results are an average of three independent experiments. Statistical significance is determined by two-tailed Student’s t-test (**P < 0.01, ***P < 0.001) and the error bars show standard deviation (SD). Source data and further statistical analysis are provided in the source data file. Observations of GFP signals in pZmSC1::ZmSC1-GFP (c) and pZmSC3::ZmSC3-GFP (d) were performed three times with similar results. FA filiform apparatus, mNU micropylar nucellus, SC synergid cell. Scale bars, 50 μm.
