Biology subjects

Bellin, L.

Publications and source records attributed to Bellin, L..

5 recordsLinked to original sources

bioRxiv2025

A non-rectifying potassium channel increases cassava drought tolerance and storage root yield

Cassava (Manihot esculenta) is an important crop for food security in the tropics, particularly for smallholder farmers in sub-Saharan Africa, where yields are often severely limited by pathogen pressure, nutrient deficiency, and water scarcity. We expressed a non-rectifying Arabidopsis thaliana potassium (K+) channel gene version, AKT2var, in the vascular tissue of cassava plants. The transgenic cassava plants had higher electron transport and CO2 assimilation rates, a higher bulk flow velocity, and increased source-sink carbohydrate transport, as demonstrated by comparative 11C-positron emission tomography and tissue-specific metabolite profiling. Cassava storage root yield was significantly increased in greenhouse experiments and in a multi-year field trial conducted under subtropical conditions. AKT2var plants were also more tolerant to drought stress and had higher storage root yield. Targeted alteration of K+ transport is therefore a promising strategy to improve cassava productivity without additional fertilizer input and in climate-adverse growing conditions.

plant biology↗

bioRxiv2024

Symplasmic phloem loading and sub-cellular transport in storage roots are key factors for carbon allocation in cassava

Cassava is a deciduous woody perennial shrub that stores large amounts of carbon and water in its storage roots. Previous studies have shown that assimilate unloading into storage roots happens symplasmically once secondary anatomy is established. However, mechanisms controlling phloem loading and overall carbon partitioning to different cassava tissues remain unclear. Here we used a combination of histological, transcriptional, and biochemical analyses on different cassava tissues and timepoints to better understand source-sink carbon allocation. We find that cassava likely utilizes a predominantly passive symplasmic phloem loading strategy, indicated by the lack of expression of genes coding for key players of sucrose transport, the existence of branched plasmodesmata in the companion cell/bundle sheath interface of minor leaf veins, and very high leaf sucrose concentrations. Furthermore, we show that tissue-specific changes in anatomy and NSC contents are associated with tissue-specific modification in gene expression for sucrose cleavage/synthesis, as well as subcellular compartmentalization of sugars. Overall, our data suggest that carbon allocation during storage root filling is mostly facilitated symplasmically, and is likely mostly regulated by local tissue demand and subcellular compartmentalization.

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↗

bioRxiv2021

Pyrimidine nucleotide availability is essential for efficient photosynthesis, ROS scavenging, and organelle development

Nucleotide limitation and imbalance is a well described phenomenon in animal research but understudied in the plant field. A peculiarity of pyrimidine de novo synthesis in plants is the complex subcellular organization. Here, we studied two organellar localized enzymes in the pathway, with chloroplast aspartate transcarbamoylase (ATC), and mitochondrial dihydroorotate dehydrogenase (DHODH). ATC knockdowns were most severely affected, exhibiting low levels of pyrimidine nucleotides, a low energy state, reduced photosynthetic capacity and accumulation of reactive oxygen species (ROS). Furthermore, altered leaf morphology and chloroplast ultrastructure were observed in ATC mutants. Although less affected, DHODH knockdown mutants showed impaired seed germination and altered mitochondrial ultrastructure. Transcriptome analysis of an ATC-amiRNA line revealed massive alterations in gene expression with central metabolic pathways being downregulated and stress response and RNA related pathways being upregulated. In addition, genes involved in central carbon metabolism, intracellular transport and respiration were mainly downregulated in ATC mutants, being putatively responsible for the observed impaired growth. ONE-SENTENCE SUMMARYImpaired pyrimidine nucleotide synthesis results in nucleotide limitation and imbalance, resulting in impaired photosynthesis, reduced growth, reproduction, and seed yield together with massively altered gene expression

plant biology↗

bioRxiv2020

UMP inhibition and sequential firing in aspartate transcarbamoylase open ways to regulate plant growth

Pyrimidine nucleotides are essential to plant development. We proved that Arabidopsis growth can be inhibited or enhanced by down- or upregulating aspartate transcarbamoylase (ATC), the first committed enzyme for de novo biosynthesis of pyrimidines in plants. To understand the unique mechanism of feedback inhibition of this enzyme by uridine 5-monophosphate (UMP), we determined the crystal structure of the Arabidopsis ATC trimer free and bound to UMP, demonstrating that the nucleotide binds and blocks the active site. The regulatory mechanism relies on a loop exclusively conserved in plants, and a single-point mutation (F161A) turns ATC insensitive to UMP. Moreover, the structures in complex with a transition-state analog or with carbamoyl phosphate proved a mechanism in plant ATCs for sequential firing of the active sites. The disclosure of the unique regulatory and catalytic properties suggests new strategies to modulate ATC activity and to control de novo pyrimidine synthesis and plant growth.

plant biology↗