Biology subjects

Sultan, L. D.

Publications and source records attributed to Sultan, L. D..

4 recordsLinked to original sources

bioRxiv2024

The thylakoid lumen Deg1 protease affects non-photochemical quenching via the levels of violaxanthin de-epoxidase and PsbS

Non-photochemical quenching (NPQ), the dissipation of excess light energy as heat, has been long recognized as a major protective mechanism that minimizes the potential for oxidative damage to photosystem II (PSII) reaction centers. Two major positive contributors to NPQ are the carotenoid zeaxanthin, generated from violaxanthin by the enzyme violaxanthin de-epoxidase (VDE or NPQ1), and the thylakoid protein PsbS (NPQ4). The involvement of the lumenal Deg proteases in the repair of PSII from photoinhibition prompted us to further explore their possible role in other responses of Arabidopsis thaliana to high light. Here we show that upon exposure to high light, the single deg1 and the triple deg158 mutants display different levels and kinetics of NPQ, compared to the deg58 mutant and WT that behave alike. In response to high light, the two genotypes lacking Deg1 over-accumulate NPQ1 and NPQ4. After temporal inhibition of protein translation in vivo, the level of these two proteins in deg1 is higher than in WT. Together, the results suggest that Deg1 represents a new level of regulation of the NPQ process through adjusting the quantity of NPQ1 and NPQ4 proteins, probably through their proteolysis.

plant biology↗

bioRxiv2020

Insights into the mitochondrial transcriptome landscapes of two Brassicales plant species, Arabidopsis thaliana (var. Col-0) and Brassica oleracea (var. botrytis)

Mitochondria play key roles in cellular energy metabolism within eukaryotic cells. As relics of endosymbiotic bacteria, most (but not all) mitochondria contain their own genome (mitogenome, mtDNA), as well as intrinsic biosynthetic machinery for making organelle RNAs and proteins. The expression of the mtDNA requires regulated metabolism of its transcriptome by nuclear-encoded factors. Post-transcriptional mtRNA modifications play a central role in the expression of the plant mitogenomes, and hence in organellar biogenesis and plant physiology. Despite extensive investigations, a full map of angiosperm mitochondrial transcriptomes, a prerequisite for the elucidation of the basic RNA biology of mitochondria, has not been reported yet. Using RNA-seq data, RT-PCR and bioinformatics, we sought to explore the gene expression profiles of land plant mitochondria. Here, we present the mitochondrial transcriptomic maps of two key Brassicaceae species, Arabidopsis thaliana (var Col-0) and cauliflower (Brassica oleracea var. botrytis). The revised transcriptome landscapes of Arabidopsis and cauliflower mitogenomes provide with more detail into mtRNA biology and processing in angiosperm mitochondria, and we expect that they would serve as a valuable resource for the plant organellar community. Accession numbersSequences are available at the Sequence Read Archive (accession no. PRJNA472433), for both Arabidopsis thaliana var. Col-0 mtRNA (SRA no. SRX4110179) and Brassica oleracea var. botrytis mtRNA (SRA no. SRX4110177).

plant biology↗

bioRxiv2019

The unique topologies of N6-Adenosine methylation (m6A) in land-plant mitochondria and their putative effects on organellar gene-expression

Mitochondria are the main source of ATP production and also contribute to many other processes central to cellular function. Mitochondrial activities have been linked with growth, differentiation and aging. As relicts of bacterial endosymbionts, these organelles contain their own genetic system (i.e., mitogenome or mtDNA). The expression of the mtDNA in plants is complex, particularly at the posttranscriptional level. Following transcription, the polycistronic pre-RNAs in plant mitochondria are processed into individual RNAs, which then undergo extensive modifications, as trimming, splicing and C[->]U editing, before being translated by organellar ribosomes. Our study focuses on N6-methylation of Adenosine ribonucleotides (m6A-RNA) in plant mitochondria. m6A is the most common modification in eukaryotic mRNAs. The biological significance of this highly dynamic modification is under investigation, but its widely accepted that m6A mediates structural switches that affect RNA stability and activity. By performing m6A-pulldown/RNA-seq (m6A-RIP-seq) analyses of Arabidopsis and cauliflower mitochondrial transcripts (mtRNAs), we provide with detail information on the m6A landscapes in angiosperms mitochondria. The results indicate that m6A targets different types of mtRNAs, including coding sequences, UTRs, introns and non-coding RNA species. While introns and noncoding-RNAs undergo multiple m6A modifications along the transcript, in mRNAs m6A-modifications are preferably positioned near start-codons, and may modulate the translatability of the m6A-modified transcripts.

molecular biology↗

bioRxiv2019

Astaxanthin extends lifespan via altered biogenesis of the mitochondrial respiratory chain complex III

Astaxanthin is a keto-carotenoid produced in some bacteria and algae, which has very important industrial applications (i.e., in cosmetics, coloring additive in aquaculture and as a dietary supplement for human). Here, we analyzed the molecular basis of Astaxanthin-mediated prolongevity in the model organism, Caenorhabditis elegans. The increased lifespan effects of Astaxanthin are restricted in C. elegans to the adult phase and are uninfluenced by various other carotenoids tested. Genetic analyses indicated that the Astaxanthin-mediated life-extension relies on mitochondria activity, via the Rieske iron-sulfur polypeptide-1 (ISP-1), but is not influenced by the functions of other known longevity-related gene-loci, including CLK-1, DAF-2, DAT-16, EAT-2, GAS-1 GLP-1 or MEV-1. Biochemical analyses of native respiratory complexes showed that Astaxanthin affects the biogenesis of holo-complex III (and likely supercomplex I+III, as well). Effects on holo-CIII assembly and activity were also indicated by in-vitro assays, with mitochondria isolated from worms, rodents, human and plants, which were treated with Astaxanthin. These data indicated a cross-species effect on the oxidative phosphorylation (OXPHOS) machinery by the carotenoid, and provide with further insights into the molecular mechanism of animals longevity extension by Astaxanthin.\n\nSignificance StatementAstaxanthin is a widely consumed pigment by animals and human. In this study we find that Astaxanthin, but not other tested carotenoids, significantly extends the lifespan of animals by affecting respiratory complex III (CIII) biogenesis of the mitochondria, in plants, C. elegans, rodents and human. We further propose a model to try explaining this effect of astaxanthin on animals longevity.

developmental biology↗