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Embryo development in Arabidopsis (Arabidopsis thaliana) starts off with an asymmetric division of the zygote to generate the precursors of the embryo proper and the supporting extraembryonic suspensor. The suspensor degenerates as the development of the embryo proper proceeds beyond the heart stage. Until the globular stage, the suspensor maintains embryonic potential and can form embryos in the absence of the developing embryo proper. We report a mutant called meerling-1 (mrl-1), which shows a high penetrance of suspensor-derived polyembryony due to delayed development of the embryo proper. Eventually, embryos from both apical and suspensor lineages successfully develop into normal plants and complete their life cycle. We identified the causal mutation as a genomic rearrangement altering the promoter of the Arabidopsis U3 SMALL NUCLEOLAR RNA-ASSOCIATED PROTEIN 18 (UTP18) homolog that encodes a nucleolar-localized WD40-repeat protein involved in processing 18S preribosomal RNA. Accordingly, root-specific knockout of UTP18 caused growth arrest and accumulation of unprocessed 18S pre-rRNA. We generated the mrl-2 loss-of-function mutant and observed asynchronous megagametophyte development causing embryo sac abortion. Together, our results indicate that promoter rearrangement decreased UTP18 protein abundance during early stage embryo proper development, triggering suspensor-derived embryogenesis. Our data support the existence of noncell autonomous signaling from the embryo proper to prevent direct reprogramming of the suspensor toward embryonic fate.

we report a novel mutant called meerling-1 (mrl-1), which shows a high penetrance of suspensor derived polyembryony. In mrl-1, ectopic embryos develop upon delayed development of the embryo proper. Eventually, embryos from both lineages successfully develop into normal plants and complete their life cycle. We identified the causal mutation as a genomic rearrangement altering the promoter of the Arabidopsis UTP18 homolog that encodes a nucleolar localized WD40-repeat protein involved in processing 18S pre-ribosomal RNA., we report a novel mutant called meerling-1 (mrl-1), which shows a high penetrance of suspensor derived polyembryony. In mrl-1, ectopic embryos develop upon delayed development of the embryo proper. Eventually, embryos from both lineages successfully develop into normal plants and complete their life cycle. We identified the causal mutation as a genomic rearrangement altering the promoter of the Arabidopsis UTP18 homolog that encodes a nucleolar localized WD40-repeat protein involved in processing 18S pre-ribosomal RNA.

Organ formation in animals and plants relies on precise control of cell state transitions to turn stem cell daughters into fully differentiated cells. In plants, cells cannot rearrange due to shared cell walls. Thus, differentiation progression and the accompanying cell expansion must be tightly coordinated. PLETHORA (PLT) transcription factor gradients were shown to guide the progression of cell differentiation at different positions in the Arabidopsis root. While well-described transcription factor gradients in animals specify distinct cell fates within an essentially static context, the PLT gradient is unique in its ability to control cell differentiation in a growing organ during continuous production and expansion of cells. To understand the output of these gradients we studied the gene set transcriptionally controlled by PLTs. Our work reveals how the PLT gradient regulates cell state by region-specific induction of cell proliferation genes and repression of differentiation. Moreover, PLT targets include major patterning genes and autoregulatory feedback components, reinforcing their role as master regulators of organ development., Organ formation in animals and plants relies on precise control of cell state transitions to turn stem cell daughters into fully differentiated cells. In plants, cells cannot rearrange due to shared cell walls. Thus, differentiation progression and the accompanying cell expansion must be tightly coordinated. PLETHORA (PLT) transcription factor gradients were shown to guide the progression of cell differentiation at different positions in the Arabidopsis root. While well-described transcription factor gradients in animals specify distinct cell fates within an essentially static context, the PLT gradient is unique in its ability to control cell differentiation in a growing organ during continuous production and expansion of cells. To understand the output of these gradients we studied the gene set transcriptionally controlled by PLTs. Our work reveals how the PLT gradient regulates cell state by region-specific induction of cell proliferation genes and repression of differentiation. Moreover, PLT targets include major patterning genes and autoregulatory feedback components, reinforcing their role as master regulators of organ development.

Organ formation in animals and plants relies on precise control of cell state transitions to turn stem cell daughters into fully differentiated cells. In plants, cells cannot rearrange due to shared cell walls. Thus, differentiation progression and the accompanying cell expansion must be tightly coordinated. PLETHORA (PLT) transcription factor gradients were shown to guide the progression of cell differentiation at different positions in the Arabidopsis root. While well-described transcription factor gradients in animals specify distinct cell fates within an essentially static context, the PLT gradient is unique in its ability to control cell differentiation in a growing organ during continuous production and expansion of cells. To understand the output of these gradients we studied the gene set transcriptionally controlled by PLTs. Our work reveals how the PLT gradient regulates cell state by region-specific induction of cell proliferation genes and repression of differentiation. Moreover, PLT targets include major patterning genes and autoregulatory feedback components, reinforcing their role as master regulators of organ development., Organ formation in animals and plants relies on precise control of cell state transitions to turn stem cell daughters into fully differentiated cells. In plants, cells cannot rearrange due to shared cell walls. Thus, differentiation progression and the accompanying cell expansion must be tightly coordinated. PLETHORA (PLT) transcription factor gradients were shown to guide the progression of cell differentiation at different positions in the Arabidopsis root. While well-described transcription factor gradients in animals specify distinct cell fates within an essentially static context, the PLT gradient is unique in its ability to control cell differentiation in a growing organ during continuous production and expansion of cells. To understand the output of these gradients we studied the gene set transcriptionally controlled by PLTs. Our work reveals how the PLT gradient regulates cell state by region-specific induction of cell proliferation genes and repression of differentiation. Moreover, PLT targets include major patterning genes and autoregulatory feedback components, reinforcing their role as master regulators of organ development.

Organ formation in animals and plants relies on precise control of cell state transitions to turn stem cell daughters into fully differentiated cells. In plants, cells cannot rearrange due to shared cell walls. Thus, differentiation progression and the accompanying cell expansion must be tightly coordinated. PLETHORA (PLT) transcription factor gradients were shown to guide the progression of cell differentiation at different positions in the Arabidopsis root. While well-described transcription factor gradients in animals specify distinct cell fates within an essentially static context, the PLT gradient is unique in its ability to control cell differentiation in a growing organ during continuous production and expansion of cells. To understand the output of these gradients we studied the gene set transcriptionally controlled by PLTs. Our work reveals how the PLT gradient regulates cell state by region-specific induction of cell proliferation genes and repression of differentiation. Moreover, PLT targets include major patterning genes and autoregulatory feedback components, reinforcing their role as master regulators of organ development., Organ formation in animals and plants relies on precise control of cell state transitions to turn stem cell daughters into fully differentiated cells. In plants, cells cannot rearrange due to shared cell walls. Thus, differentiation progression and the accompanying cell expansion must be tightly coordinated. PLETHORA (PLT) transcription factor gradients were shown to guide the progression of cell differentiation at different positions in the Arabidopsis root. While well-described transcription factor gradients in animals specify distinct cell fates within an essentially static context, the PLT gradient is unique in its ability to control cell differentiation in a growing organ during continuous production and expansion of cells. To understand the output of these gradients we studied the gene set transcriptionally controlled by PLTs. Our work reveals how the PLT gradient regulates cell state by region-specific induction of cell proliferation genes and repression of differentiation. Moreover, PLT targets include major patterning genes and autoregulatory feedback components, reinforcing their role as master regulators of organ development.

Organ formation in animals and plants relies on precise control of cell state transitions to turn stem cell daughters into fully differentiated cells. In plants, cells cannot rearrange due to shared cell walls. Thus, differentiation progression and the accompanying cell expansion must be tightly coordinated. PLETHORA (PLT) transcription factor gradients were shown to guide the progression of cell differentiation at different positions in the Arabidopsis root. While well-described transcription factor gradients in animals specify distinct cell fates within an essentially static context, the PLT gradient is unique in its ability to control cell differentiation in a growing organ during continuous production and expansion of cells. To understand the output of these gradients we studied the gene set transcriptionally controlled by PLTs. Our work reveals how the PLT gradient regulates cell state by region-specific induction of cell proliferation genes and repression of differentiation. Moreover, PLT targets include major patterning genes and autoregulatory feedback components, reinforcing their role as master regulators of organ development., Organ formation in animals and plants relies on precise control of cell state transitions to turn stem cell daughters into fully differentiated cells. In plants, cells cannot rearrange due to shared cell walls. Thus, differentiation progression and the accompanying cell expansion must be tightly coordinated. PLETHORA (PLT) transcription factor gradients were shown to guide the progression of cell differentiation at different positions in the Arabidopsis root. While well-described transcription factor gradients in animals specify distinct cell fates within an essentially static context, the PLT gradient is unique in its ability to control cell differentiation in a growing organ during continuous production and expansion of cells. To understand the output of these gradients we studied the gene set transcriptionally controlled by PLTs. Our work reveals how the PLT gradient regulates cell state by region-specific induction of cell proliferation genes and repression of differentiation. Moreover, PLT targets include major patterning genes and autoregulatory feedback components, reinforcing their role as master regulators of organ development.

[EN] Natural genetic variation is crucial for adaptability of plants to different environments. Seed dormancy prevents precocious germination in unsuitable conditions and is an adaptation to a major macro-environmental parameter, the seasonal variation in temperature and day length. Here we report the isolation of IBO, a quantitative trait locus (QTL) that governs c. 30% of germination rate variance in an Arabidopsis recombinant inbred line (RIL) population derived from the parental accessions Eilenburg-0 (Eil-0) and Loch Ness-0 (Lc-0).IBO encodes an uncharacterized phosphatase 2C-related protein, but neither the Eil-0 nor the Lc-0 variant, which differ in a single amino acid, have any appreciable phosphatase activity in in vitro assays. However, we found that the amino acid change in the Lc-0 variant of the IBO protein confers reduced germination rate. Moreover, unlike the Eil-0 variant of the protein, the Lc-0 variant can interfere with the activity of the phosphatase 2C ABSCISIC ACID INSENSITIVE 1 in vitro. This suggests that the Lc-0 variant possibly interferes with abscisic acid signaling, a notion that is supported by physiological assays. Thus, we isolated an example of a QTL allele with a nonsynonymous amino acid change that might mediate local adaptation of seed germination timing.