A dynamic ubiquitination balance of cell proliferation and endoreduplication regulators determines plant organ size.

Ubiquitination plays a crucial role throughout plant growth and development. The E3 ligase DA2 has been reported to activate the peptidase DA1 by ubiquitination, hereby limiting cell proliferation. However, the molecular mechanisms that regulate DA2 remain elusive.

Distinct cellular strategies determine sensitivity to mild drought of Arabidopsis natural accessions.

The worldwide distribution of Arabidopsis (Arabidopsis thaliana) accessions imposes different types of evolutionary pressures, which contributes to various responses of these accessions to environmental stresses. Responses to drought stress have mostly been studied in the Columbia accession, which is predominantly used in plant research. However, the reactions to drought stress are complex and our understanding of the responses that contribute to maintaining plant growth during mild drought (MD) is very limited.

Post-translational modifications regulate the activity of the growth-restricting protease DA1.

Plants are a primary food source and can form the basis for renewable energy resources. The final size of their organs is by far the most important trait to consider when seeking increased plant productivity. Being multicellular organisms, plant organ size is mainly determined by the coordination between cell proliferation and cell expansion.

UBP12 and UBP13 negatively regulate the activity of the ubiquitin-dependent peptidases DA1, DAR1 and DAR2.

Protein ubiquitination is a very diverse post-translational modification leading to protein degradation or delocalization, or altering protein activity. In , two E3 ligases, BIG BROTHER (BB) and DA2, activate the latent peptidases DA1, DAR1 and DAR2 by mono-ubiquitination at multiple sites. Subsequently, these activated peptidases destabilize various positive growth regulators.

Functional analysis of Arabidopsis and maize transgenic lines overexpressing the ADP-ribose/NADH pyrophosphohydrolase, AtNUDX7.

The conserved poly(ADP-ribosyl)ation (PAR) pathway consists of three genetic components that are potential targets to modulate the plant's energy homeostasis upon stress with the aim to improve yield stability in crops and help secure food supply. We studied the role of the PAR pathway component ADP-ribose/NADH pyrophosphohydrolase (AtNUDX7) in yield and mild drought stress by using a transgenic approach in Arabidopsis thaliana and maize (Zea mays). Arabidopsis AtNUDX7 cDNA was overexpressed in Arabidopsis and maize by means of the constitutive Cauliflower Mosaic Virus 35S promoter and the strong constitutive Brachypodium distachyon pBdEF1α promoter, respectively.

Ubiquitylation activates a peptidase that promotes cleavage and destabilization of its activating E3 ligases and diverse growth regulatory proteins to limit cell proliferation in .

The characteristic shapes and sizes of organs are established by cell proliferation patterns and final cell sizes, but the underlying molecular mechanisms coordinating these are poorly understood. Here we characterize a ubiquitin-activated peptidase called DA1 that limits the duration of cell proliferation during organ growth in The peptidase is activated by two RING E3 ligases, Big Brother (BB) and DA2, which are subsequently cleaved by the activated peptidase and destabilized. In the case of BB, cleavage leads to destabilization by the RING E3 ligase PROTEOLYSIS 1 (PRT1) of the N-end rule pathway.

Forever Young: The Role of Ubiquitin Receptor DA1 and E3 Ligase BIG BROTHER in Controlling Leaf Growth and Development.

The final size of plant organs is determined by a combination of cell proliferation and cell expansion. Leaves account for a large part of above-ground biomass and provide energy to complete the plant's life cycle. Although the final size of leaves is remarkably constant under fixed environmental conditions, several genes have been described to enhance leaf growth when their expression is modulated.

Plant Growth Beyond Limits.

Growth processes, governed by complex genetic networks in a coordinated manner, are determining factors for numerous crop traits. Many components of these networks, described in Arabidopsis and to a lesser extent in crops, enhance organ growth when perturbed. However, translating our understanding of plant growth into crop improvement has been very limited.

A Journey Through a Leaf: Phenomics Analysis of Leaf Growth in Arabidopsis thaliana.

In Arabidopsis, leaves contribute to the largest part of the aboveground biomass. In these organs, light is captured and converted into chemical energy, which plants use to grow and complete their life cycle. Leaves emerge as a small pool of cells at the vegetative shoot apical meristem and develop into planar, complex organs through different interconnected cellular events.

Combining growth-promoting genes leads to positive epistasis in Arabidopsis thaliana.

Several genes positively influence final leaf size in Arabidopsis when mutated or overexpressed. The connections between these growth regulators are still poorly understood although such knowledge would further contribute to understand the processes driving leaf growth. In this study, we performed a combinatorial screen with 13 transgenic Arabidopsis lines with an increased leaf size.

SAMBA, a plant-specific anaphase-promoting complex/cyclosome regulator is involved in early development and A-type cyclin stabilization.

The anaphase-promoting complex/cyclosome (APC/C) is a large multiprotein E3 ubiquitin ligase involved in ubiquitin-dependent proteolysis of key cell cycle regulatory proteins, including the destruction of mitotic cyclins at the metaphase-to-anaphase transition. Despite its importance, the role of the APC/C in plant cells and the regulation of its activity during cell division remain poorly understood. Here, we describe the identification of a plant-specific negative regulator of the APC/C complex, designated SAMBA.

Leaf size control: complex coordination of cell division and expansion.

Size control of multicellular organisms poses a longstanding biological question that has always fascinated scientists. Currently the question is far from being resolved because of the complexity of and interconnection between cell division and cell expansion, two different events necessary to form a mature organ. Because of the importance of plants for food and renewable energy sources, dissecting the genetic networks underlying plant growth and organ size is becoming a high priority in plant science worldwide.

Exit from proliferation during leaf development in Arabidopsis thaliana: a not-so-gradual process.

Early leaf growth is sustained by cell proliferation and subsequent cell expansion that initiates at the leaf tip and proceeds in a basipetal direction. Using detailed kinematic and gene expression studies to map these stages during early development of the third leaf of Arabidopsis thaliana, we showed that the cell-cycle arrest front did not progress gradually down the leaf, but rather was established and abolished abruptly. Interestingly, leaf greening and stomatal patterning followed a similar basipetal pattern, but proliferative pavement cell and formative meristemoid divisions were uncoordinated in respect to onset and persistence.

The APC/C subunit 10 plays an essential role in cell proliferation during leaf development.

The largest E3 ubiquitin-ligase complex, known as anaphase-promoting complex/cyclosome (APC/C), regulates the proteolysis of cell cycle regulators such as CYCLIN B and SECURIN that are essential for sister-chromatid separation and exit from mitosis. Despite its importance, the role of APC/C in plant cells and the regulation of its activity during cell division remain poorly understood. Here, the Arabidopsis thaliana APC/C subunit APC10 was characterized and shown to functionally complement an apc10 yeast mutant.

Plant structure visualization by high-resolution X-ray computed tomography.

New developments in high-resolution X-ray computed tomography (HRXCT) are promising for the broader application of this non-destructive imaging method in plant sciences. Here, we demonstrate how detailed three-dimensional morphological traits can be extracted rapidly from in vivoArabidopsis thaliana seedlings without sample manipulation. Furthermore, ex vivo scanning at sub-micron resolution allows the quantification and visualization of the cellular organization of plant tissue samples, making HRXCT a desired tool in developmental plant biology.

Hide and seek: uncloaking the vegetative shoot apex of Arabidopsis thaliana.

Leaf primordia are iteratively formed on the flanks of the shoot apical meristem (SAM) at the vegetative shoot apex of Arabidopsis thaliana. The youngest leaf primordia and the SAM are extensively covered by older proliferating leaves, making it difficult to obtain accurate volumetric data from these structures. Combination of serial histological sections combined with 3D reconstruction software allowed us to acquire such data.