Biology subjects

Richter, A. S.

Publications and source records attributed to Richter, A. S..

5 recordsLinked to original sources

bioRxiv2024

SnRK1 acts upstream of PAP1, contributing to fine-tuning flavonoid biosynthesis in high-light.

In land plants, one of the processes vital to cope with environmental changes is the accumulation of photoprotective flavonoids such as flavonols and anthocyanins. The inactivation of SUCROSE NON-FERMENTING1 RELATED PROTEIN KINASE1 (SnRK1), which acts in a chloroplast-derived sugar signalling pathway, permits the activation of flavonoid biosynthesis in high-light. The present study provides genetic evidence that SnRK1 acts upstream of PRODUCTION OF ANTHOCYANIN PIGMENT1 (PAP1), encoding a crucial transcription factor that activates the anthocyanin branch of flavonoid biosynthesis during high-light acclimation. A time-resolved expression analysis indicates a two-step suppression of MYB LIKE2 (MYBL2), a repressor of anthocyanin production, involving SnRK1 inactivation for stable anthocyanin accumulation during prolonged high-light exposure. Furthermore, overexpression of PAP1 resulted in the marked suppression of MYB11, MYB12 and MYB111 and FLAVONOL SYNTHASE1, initiating the flavonol branch of the pathway. Analysis of a flavonoid-deficient CHALCONE SYNTHASE mutant overexpressing PAP1 suggests that regulation of flavonoid biosynthesis is independent of flavonoid intermediates and end products but PAP1-dependent. It is proposed that PAP1 suppresses the flavonol branch by an as yet unknown mechanism, thereby promoting the consumption of carbon building blocks for anthocyanin production to permit the fine-tuning of the pathway.

plant biology↗

bioRxiv2023

UPP affects chloroplast development by interfering with chloroplast proteostasis

Arabidopsis uracil phosphoribosyltransferase (UPP) is an essential enzyme which appears to have a previously unknown, moonlighting activity. Our analysis of UPP amiRNA mutants has confirmed that this vital function is crucial for chloroplast development and growth. Interestingly, this function appears to be unrelated to nucleotide homeostasis since nucleotide levels were not altered in the studied mutants. Transcriptomics and proteomic analysis suggest that UPP plays a role in chloroplast proteostasis, especially under high light (HL). Immunoblots of mature plants and a de-etiolation experiment with young seedlings revealed PetC, the iron-sulfur protein of the cytochrome b6f complex, as a putative UPP target. In addition, UPP and PetC were identified in a high molecular weight complex. Consistently, we show that PetC is massively reduced in UPP knock-down plants. The block observed in photosynthetic electron transport, as evidenced by reduced high light-induced non-photochemical quenching (NPQ) but increased unregulated energy dissipation (NO), might be therefore a consequence of reduced PetC. After HL treatment, UPP amiRNA mutants showed impaired photosynthesis and reduced carbohydrate contents, resulting in an inability to induce flavonoid biosynthesis. In addition, the levels of the osmoprotectants raffinose, proline and fumarate were found to be reduced. Proteases, including thylakoid filamentation temperature-sensitive 1, 5 (FtsH), caseinolytic protease proteolytic subunit 1 (ClpP1), and processing peptidases, as well as components of the chloroplast protein import machinery, were up-regulated. In sum, our work suggests that UPP assists in stabilizing and protection of PetC during the assembly of the Fe-S cluster and targeting to the thylakoid.

molecular biology↗

bioRxiv2023

Spliceosomal complex components are critical for adjusting the C:N balance during high-light acclimation

Plant acclimation to an ever-changing environment is decisive for growth, reproduction and survival. Light availability limits biomass production on both ends of the intensity spectrum. Therefore, the adjustment of plant metabolism is central to high-light (HL) acclimation, and accumulation of photoprotective anthocyanins is commonly observed. However, mechanisms and factors regulating the HL acclimation response are less clear. Two Arabidopsis mutants of spliceosome components exhibiting a pronounced anthocyanin overaccumulation in HL were isolated from a forward genetic screen for new factors crucial for plant acclimation. Time-resolved physiological, transcriptome and metabolome analysis revealed a vital function of the spliceosome components for rapidly adjusting gene expression and metabolism. Deficiency of INCREASED LEVEL OF POLYPLOIDY1 (ILP1), NTC-RELATED PROTEIN1 (NTR1), and PLEIOTROPIC REGULATORY LOCUS1 (PRL1) resulted in a marked overaccumulation of carbohydrates and strongly diminished amino acid biosynthesis in HL. While not generally limited in N-assimilation, ilp1, ntr1, and prl1 mutants showed higher glutamate levels and reduced amino acid biosynthesis in HL. The comprehensive analysis reveals a function of the spliceosome in the conditional regulation of the carbon:nitrogen-balance and the accumulation of anthocyanins during HL acclimation. The importance of gene expression, metabolic regulation, and re-direction of carbon towards anthocyanin biosynthesis for HL acclimation are discussed.

molecular biology↗

bioRxiv2022

Triosephosphate export from chloroplasts regulates flavonoid biosynthesis and permits high light acclimation through the inactivation of SnRK1

Plants evolved multiple strategies to cope with rapid changes in the environment. During high light acclimation, biosynthesis of photoprotective flavonoids, such as anthocyanins, is induced. However, the exact nature of the signal and downstream factors for high light induction of flavonoid biosynthesis (FB) are still under debate. Here we show that carbon-fixation in chloroplasts, subsequent export of photosynthates by TRIOSEPHOSPHATE/PHOSPHATE TRANSLOCATOR (TPT), and the rapid increase in cellular sugar contents permit the transcriptional activation of FB during high light acclimation. In combination with genetic and physiological analysis, targeted and whole transcriptome gene expression studies showed that reactive oxygen species and phytohormones play only a minor role for rapid HL-induction of the anthocyanin branch of FB. In addition to FB, sugar-responsive genes were late-repressed or induced in tpt-2 in the course of the high light treatment and a significant overlap with transcripts regulated by SNF1-RELATED PROTEIN KINASE 1 (SnRK1) was found. Analysis of mutants with increased and repressed SnRK1 activity revealed that inactivation of SnRK1 is required for the rapid induction of FB during high light acclimation. Our study underlines the central role of chloroplasts as sensors for environmental changes and emphasizes the vital function of sugar-signalling in plant acclimation, even beyond the regulation of FB.

plant biology↗

bioRxiv2018

snakePipes enable flexible, scalable and integrative epigenomic analysis

The scale and diversity of epigenomics data has been rapidly increasing and ever more studies now present analyses of data from multiple epigenomic techniques. Performing such integrative analysis is time-consuming, especially for exploratory research, since there are currently no pipelines available that allow fast processing of datasets from multiple epigenomic assays while also allow for flexibility in running or upgrading the workflows. Here we present a solution to this problem: snakePipes, which can process and perform downstream analysis of data from all common epigenomic techniques (ChIP-seq, RNA-seq, Bisulfite-seq, ATAC-seq, Hi-C and single-cell RNA-seq) in a single package. We demonstrate how snakePipes can simplify integrative analysis by reproducing and extending the results from a recently published large-scale epigenomics study with a few simple commands. snakePipes are available under an open-source license at https://github.com/maxplanck-ie/snakepipes.

genomics↗