Kurt Hoogewijs

GOLVEN Secretory Peptides Regulate Auxin Carrier Turnover during Plant Gravitropic Responses

Growth and development are coordinated by an array of intercellular communications. Known plant signaling molecules include phytohormones and hormone peptides. Although both classes can be implicated in the same developmental processes, little is known about the interplay between phytohormone action and peptide signaling within the cellular microenvironment. We show that genes coding for small secretory peptides, designated GOLVEN (GLV), modulate the distribution of the phytohormone auxin. The deregulation of the GLV function impairs the formation of auxin gradients and alters the reorientation of shoots and roots after a gravity stimulus. Specifically, the GLV signal modulates the trafficking dynamics of the auxin efflux carrier PIN-FORMED2 involved in root tropic responses and meristem organization. Our work links the local action of secretory peptides with phytohormone transport.

Transcriptional and Functional Classification of the GOLVEN/ROOT GROWTH FACTOR/CLE-Like Signaling Peptides Reveals Their Role in Lateral Root and Hair Formation

Summary: The expression domains and phenotypes associated with distinct members of the GLV/RFG/CLEL secreted peptide family indicate that they function in multiple developmental programs, including meristem maintenance, gravitropism, lateral root emergence, and the formation of root hairs. The GOLVEN (GLV)/ROOT GROWTH FACTORS/CLE-Like small signaling peptide family is encoded by 11 genes in Arabidopsis (Arabidopsis thaliana). Some of them have already been shown to control root meristem maintenance, auxin fluxes, and gravitropic responses. As a basis for the detailed analysis of their function, we determined the expression domains for each of the 11 GLV genes with promoter-reporter lines. Although they are collectively active in all examined plant parts, GLV genes have highly specific transcription patterns, generally restricted to very few cells or cell types in the root and shoot and in vegetative and reproductive tissues. GLV functions were further investigated with the comparative analysis of root phenotypes induced by gain- and loss-of-function mutants or in treatments with GLV-derived synthetic peptides. We identified functional classes that relate to the gene expression domains in the primary root and suggest that different GLV signals trigger distinct downstream pathways. Interestingly, GLV genes transcribed at the early stages of lateral root development strongly inhibited root branching when overexpressed. Furthermore, transcription patterns together with mutant phenotypes pointed to the involvement of GLV4 and GLV8 in root hair formation. Overall, our data suggest that nine GLV genes form three subgroups according to their expression and function within the root and offer a comprehensive framework to study the role of the GLV signaling peptides in plant development.

The SBT6.1 subtilase processes the GOLVEN1 peptide controlling cell elongation

Highlight Maturation of GLV signaling peptides requires two SBT6 subtilases. SBT6 proteolytic activity is further regulated by the Serpin1 inhibitor, implying a complex network that controls cell elongation in Arabidopsis.

Singlet Oxygen-Induced Furan Oxidation for Site-Specific and Chemoselective Peptide Ligation

A novel chemoselective ligation methodology has been developed for the facile construction of peptide-based fluorescent probes. Furan-containing peptides were activated by singlet oxygen and covalently engaged by nitrogen nucleophiles to yield stable conjugates. Singlet oxygen was compatible with sensitive amino acid residues within the peptides and a range of fluorophores, bearing different functionalities, were successfully incorporated, illustrating the broad scope of the developed strategy.

Aromatic capping surprisingly stabilizes furan moieties in peptides against acidic degradation

We herein describe the synthesis of furan containing peptides for further post-synthetic derivatisation in solution through our recently developed furan-oxidation-labeling technology. Previously, it was reported by others that during acidic cleavage of furan-modified peptides, furan moieties can suffer from degradation. We demonstrate here that this degradation is position dependent and can be fully suppressed through introduction of proximate aromatic residues. Versatile introduction of 2-furylalanine at internal, C-terminal as well as the sensitive N-terminal positions has now been proven possible.

Advances in methods for reducing mitochondrial DNA disease by replacing or manipulating the mitochondrial genome

Mitochondrial DNA (mtDNA) is a multi-copy genome whose cell copy number varies depending on tissue type. Mutations in mtDNA can cause a wide spectrum of diseases. Mutated mtDNA is often found as a subset of the total mtDNA population in a cell or tissue, a situation known as heteroplasmy. As mitochondrial dysfunction only presents after a certain level of heteroplasmy has been acquired, ways to artificially reduce or replace the mutated species have been attempted. This review addresses recent approaches and advances in this field, focusing on the prevention of pathogenic mtDNA transfer via mitochondrial donation techniques such as maternal spindle transfer and pronuclear transfer in which mutated mtDNA in the oocyte or fertilized embryo is substituted with normal copies of the mitochondrial genome. This review also discusses the molecular targeting and cleavage of pathogenic mtDNA to shift heteroplasmy using antigenomic therapy and genome engineering techniques including Zinc-finger nucleases and transcription activator-like effector nucleases. Finally, it considers CRISPR technology and the unique difficulties that mitochondrial genome editing presents.

The Causes and Consequences of Nonenzymatic Protein Acylation

Thousands of protein acyl modification sites have now been identified in vivo. However, at most sites the acylation stoichiometry is low, making functional enzyme-driven regulation in the majority of cases unlikely. As unmediated acylation can occur on the surface of proteins when acyl-CoA thioesters react with nucleophilic cysteine and lysine residues, slower nonenzymatic processes likely underlie most protein acylation. Here, we review how nonenzymatic acylation of nucleophilic lysine and cysteine residues occurs; the factors that enhance acylation at particular sites; and the strategies that have evolved to limit protein acylation. We conclude that protein acylation is an unavoidable consequence of the central role of reactive thioesters in metabolism. Finally, we propose a hypothesis for why low-stoichiometry protein acylation is selected against by evolution and how it might contribute to degenerative processes such as aging.