Specification and regulation of vascular tissue identity in the Arabidopsis embryo

Abstract

Development of plant vascular tissues involves tissue identity specification, growth, pattern formation and cell-type differentiation. Although later developmental steps are understood in some detail, it is still largely unknown how the tissue is initially specified. We used the early Arabidopsis embryo as a simple model to study this process. Using a large collection of marker genes, we found that vascular identity was specified in the 16-cell embryo. After a transient precursor state, however, there was no persistent uniform tissue identity. Auxin is intimately connected to vascular tissue development. We found that, although an AUXIN RESPONSE FACTOR5/MONOPTEROS (ARF5/MP)-dependent auxin response was required, it was not sufficient for tissue specification. We therefore used a large-scale enhanced yeast one-hybrid assay to identify potential regulators of vascular identity. Network and functional analysis of candidate regulators suggest that vascular identity is under robust, complex control. We found that one candidate regulator, the G-class bZIP transcription factor GBF2, can modulate vascular gene expression by tuning MP output through direct interaction. Our work uncovers components of a gene regulatory network that controls the initial specification of vascular tissue identity.

Gene Expression Variation in Arabidopsis Embryos at Single-Nucleus Resolution

“…The mean expression values of all nuclei within each cluster were used to perform tissue enrichment tests as previously described (Schon and Nodine, 2017) and to calculate Spearman’s correlation coefficients with published globular stage embryo proper (32E) and suspensor (32S) samples (Zhou et al, 2020). The expression levels of selected markers and three recently reported genes ( PEAR1/AT2G37590 , DOF6/AT3G45610 and GATA20/AT2G18380 ) (Smit et al, 2020) not included in our reference marker table for tissue score calculation were plotted with Monocle3’s plot_genes_by_group() function.…”

An Artificial Conversion of Roots into Organs with Shoot Stem Characteristics by Inducing Two Transcription Factors

“…To investigate spatiotemporal expression of the up-regulated genes CUC and WUS , we introduced the pCUC2 : VENUS ( Heisler et al., 2005 ) and pWUS : dsRed ( Reddy and Meyerowitz, 2005 ) reporter genes into the ATHB25/REM7-ind plants and observed these gene expressions spatiotemporally ( Figure 5 : Figure S10 ). The expression of CUC2 gene, which is required for embryonic apical meristem formation, was observed in the whole roots especially in the nascent regions (elongation zone) generated from the RMs after the estradiol induction ( Figure 5 A: Figure S10 ), in addition to the regions around the apical meristems of shoot and main and lateral roots, where the CUC2 expression was normally expressed ( Figure 5 B: Figure S10 ) ( Smit et al., 2020 ). The WUS expression was observed in nascent regions and root cap on day 3 and later after the induction ( Figures 5 C–5E: Figures S10 and S11 ).…”

TheArabidopsisembryo as a quantifiable model for studying pattern formation

“…Moreover, the availability of the gene expression data boosted establishment of important molecular markers allowing for tracking specification processes in the root stem cell niche and vascular tissues (Smit et al, 2020). Collectively, embryonic tissueand cell-specific gene expression datasets became an invaluable resource for studying establishment of cell identity.…”

“…is quantitative reporter has been successfully used to visualise auxin response in specific embryonic tissues, such as vasculature, ground tissue, protoderm, hypophysis and suspensor (Möller et al, 2017;Roodbarkelari et al, 2015;Smit et al, 2020).…”