Transcriptional Activation of Arabidopsis Zygotes Is Required for Their Initial Division

Abstract

Commonly referred to as the maternal-to-zygotic transition, the shift of developmental control from maternal-to-zygotic genomes is a key event during animal and plant embryogenesis.Together with the degradation of parental gene products, the increased transcriptional activities of the zygotic genome remodels the early embryonic transcriptome during this transition.Although evidence from multiple flowering plants suggests that zygotes become transcriptionally active soon after fertilization, the timing and developmental requirements of zygotic genome activation in Arabidopsis thaliana (Arabidopsis) remained a matter of debate until recently. In this report, we optimized an expansion microscopy technique for robust immunostaining of Arabidopsis ovules and seeds. This enabled the detection of marks indicative of active transcription in zygotes before the first cell division. Moreover, we employed a live-imaging culture system together with transcriptional inhibitors to demonstrate that such active transcription is required in zygotes. Our results indicate that zygotic genome activation occurs soon after fertilization and is physiologically required prior to the initial zygotic division in Arabidopsis. T. (2013) Gene expression profiles in rice gametes and zygotes: identification of gamete-enriched genes and up-or down-regulated genes in zygotes after fertilization. Transcriptomes of isolated Oryza sativa gametes characterized by deep sequencing: evidence for distinct sex-dependent chromatin and epigenetic states before fertilization. Plant J., 76, 729-741.

Gene expression variation in Arabidopsis embryos at single-nucleus resolution

“…For example, in animals it has been long recognized that maternal gene products control initial pattern formation before the transition of control from the maternal to the zygotic genome (Lee et al, 2014;Tadros and Lipshitz, 2009). By contrast, transcriptional activation of the zygotic genome soon after fertilization is necessary for zygote elongation and initial divisions in Nicotiana tabacum (tobacco) (Zhao et al, 2011) and the model flowering plant Arabidopsis thaliana (Arabidopsis) (Kao and Nodine, 2019;Zhao et al, 2019). In addition, the vast majority of genes regulating Arabidopsis embryo morphogenesis are zygotically expressed (Nodine and Bartel, 2012;Zhao et al, 2019) and required (Meinke, 2019;Muralla et al, 2011).…”

Gene Expression Variation in Arabidopsis Embryos at Single-Nucleus Resolution

“…For example, in animals it has been long recognized that maternal gene products control initial pattern formation before the transition of control from the maternal to the zygotic genome (Lee et al, 2014;Tadros and Lipshitz, 2009). By contrast, transcriptional activation of the zygotic genome soon after fertilization is necessary for zygote elongation and initial divisions in Nicotiana tabacum (tobacco) (Zhao et al, 2011) and the model flowering plant Arabidopsis thaliana (Arabidopsis) (Kao and Nodine, 2019;Zhao et al, 2019). In addition, the vast majority of genes regulating Arabidopsis embryo morphogenesis are zygotically expressed (Nodine and Bartel, 2012;Zhao et al, 2019) and required (Meinke, 2019;Muralla et al, 2011).…”

Maize RAMOSA3 accumulates in nuclear condensates enriched in RNA POLYMERASE II isoforms during the establishment of axillary meristem determinacy

“…To verify this protocol was consistent with previous results using semithin sections 13 , we confirmed RA3 localization in cytoplasmic and nuclear speckles in the cells subtending developing SPMs in wild type (B73) (Figure 1A and C). We used ra3 mutant ears as a negative control to verify antibody specificity, as suggested in similar protocols 21 , and as expected no signal was detected (Figure 1B). Since RA3 expression was found in a limited number of cells, we used a positive control, anti-YSPTSPS repeat from the C-terminal domain of RNA polymerase II (POL II-CTD) phosphorylated on serine 2 (Ser2 Pho) as a constitutive nuclear marker, and found uniform nuclear immunostaining throughout the whole inflorescence, including in cells where RA3 was expressed, corroborating the technical consistency in our immunolabeling protocol (Figure 1A-B).…”