Biology subjects

Siadjeu, C.

Publications and source records attributed to Siadjeu, C..

7 recordsLinked to original sources

bioRxiv2026

Floral scent diversity and evolution in deceptive Cypripedium, and post-pollination effects on floral scent and its biosynthesis in C. henryi

Background and Aims: Floral scent is a primary driver of pollinator attraction and reproductive isolation in deceptive orchids. Yet, little is known about the variation and evolution of scent in a phylogenetic framework and how pollination affects the biosynthesis and emission of scents in these lineages. This study characterizes scent diversity across Cypripedium, a genus of deceptive orchids, examines phylogenetic constraints, and investigates post-pollination effects on scent composition in one of the species. Methods: Floral volatile organic compounds (VOCs) were sampled from 31 Cypripedium taxa using dynamic headspace techniques, and analysed by gas chromatography coupled to mass spectrometry (GC/MS). Uni- and multivariate methods were used to analyse intra- and interspecific scent variation and test for phylogenetic signal in floral scent. Post-pollination effects on scent composition were experimentally tested in C. henryi using four pollination treatments, combined with RNA-seq analyses of floral tissues to examine transcriptional responses in VOC biosynthetic pathways. Key results: We detected 258 floral VOCs, revealing a high chemical diversity dominated by terpenoids, aliphatics, and aromatic compounds. Floral scent composition was highly species-specific, and closely related taxa often shared only few compounds. Scent composition differed among pollination groups, but these groups explained only a limited proportion of overall scent variation. We detected a significant but weak phylogenetic signal, suggesting limited evolutionary constraint in floral scent. Pollination had limited effect on C. henryis floral scent and volatile biosynthesis gene expression, despite a significant decrease in total scent emission after pollinium deposition. Transcriptional changes predominantly occurred in the petals rather than the labellum and staminode. Conclusion: Floral scent evolution in Cypripedium is characterized by high chemical diversity, and a weak phylogenetic constraint, consistent with variable selection in food-deceptive systems. The pollination study further suggests the absence of a strong, directed post-pollination effect on the floral scent of C. henryi. Keywords: Cypripedium; deceptive pollination; floral scent; volatile organic compounds (VOCs); phylogenetic signal; linalool; post-pollination effects; transcriptome profiles; differential gene expression; floral organs

plant biology↗

bioRxiv2026

Insights into the functional and genetic basis of heteranthery in Arthrostemma ciliatum Pav. ex D.Don (Melastomataceae)

BackgroundMelastomes are well known for their striking diversity in stamen morphologies mostly adapted to buzz pollination by bees. The variously modified connective appendages and heteranthery in the family have fascinated botanists for more than two centuries and a variety of functions associated with pollination have been discovered for these staminal traits over the years. The repeated evolutionary shifts in these traits have been linked to pollinator shifts, likely contributing to diversification in the family. The evolutionary lability of staminal traits, especially the connective morphology, led us to hypothesize that these traits might be controlled by relatively simple genetic mechanisms and we here take the first steps to test this hypothesis by using a comparative transcriptomics approach with Arthrostemma ciliatum as our model. We also tested the functional significance of heteranthery and whether the classical division of labour hypothesis holds true for this species by comparing the number, size and viability of pollen in the two stamen types. ResultsStaminal development of this species was studied and suitable stages for transcriptome comparisons were identified. Differential expression analyses between the morphologically distinct stamen whorls at four developmental stages showed the differential expression of several transcripts involved in stamen development/elongation. Pollen comparisons between the two whorls showed that the antepetalous/inner whorl stamens have a significantly higher number of pollen and higher germination rates while the antesepalous/outer whorl stamens have significantly larger pollen. ConclusionsWe identified Jasmonate and Gibberellin signalling pathway genes (JAZ, GID1, DELLA and ARF homologs), EPF/EPFL family genes, autophagy related genes (VPE homologs) and S Locus ELF homologs as putative candidates involved in causing staminal dimorphism in A. ciliatum. Our results indicate that, for the heterantherous morph of this species, the shorter stamens (antepetalous/inner whorl) have both pollinating and feeding functions contradicting the division of labour theory. We also report the possible existence of heterostyly in A. ciliatum as an outbreeding mechanism.

evolutionary biology↗

bioRxiv2024

Dsg2 truncation causes a lethal barrier breakdown in mice

Inflammatory bowel diseases (IBD) such as Crohns disease (CD) have a complex aetiology with alterations of both the intestinal epithelial barrier and the IL23/IL17 immune response. Here, we investigated the role of a novel mutation in the desmosomal cadherin desmoglein 2 gene (DSG2) in the pathogenesis of IBD. DSG2 is known to regulate intestinal epithelial barrier integrity. Genetic analysis of a CD patient revealed a novel likely pathogenic DSG2 mutation leading to a truncated protein lacking part of the intracellular domain. We generated an enterocyte-specific mouse model, recapitulating the human mutation to study how the cytoplasmic truncation of Dsg2 affects intestinal barrier properties systemically. Moreover, we analysed the intestinal genetic profile in these mice and compared it to IBD patients. We describe a first CD patient with a rare mutation in the DSG2 gene causing cytoplasmic truncation with affects Dsg2 mobility. Mice with enterocyte-specific Dsg2 truncation suffered from a lethal intestinal barrier defect and presented a skewed IL17 response similar to CD patients. We identified the desmosomal cadherin Dsg2 as a regulator of the skewed IL17 response. These data indicate that desmosomes regulate inflammation similar to psoriasis which explains why the same novel immune therapies are effective for both diseases.

cell biology↗

bioRxiv2023

C4-like Sesuvium sesuvioides (Aizoaceae) exhibits CAM in cotyledons and putative C4+CAM metabolism in adult leaves as revealed by transcriptome analysis

The co-occurrence of C4 and CAM photosynthesis in a single species seems to be unusual and rare, probably because of the difficulty to co-regulate both pathways effectively. Nevertheless, it represents a unique chance in gaining new insights into the evolution and regulation of these complex pathways. Comparative transcriptomics using RNA-seq revealed C4-like and CAM photosynthesis in Sesuvium sesuvioides (Aizoaceae) leaves and cotyledons, respectively. When compared to cotyledons, phosphoenolpyruvate carboxylase 4 (PEPC4) and some key C4 genes were found to be up regulated in leaves. During the day, the expression of NADP-dependent malic enzyme (NADP-ME) was significantly higher in cotyledons than in leaves. The acidity titration confirmed higher acidity in the morning than in the previous evening indicating the induction of weak CAM in cotyledons by environmental conditions. Comparison of the leaves of S. sesuvioides (C4-like) and S. portulacastrum (C3) revealed that PEPC1 was significantly higher in S. sesuvioides, while PEPC3 and PEPC4 were up-regulated in S. portulacastrum. Finally, potential key regulatory elements involved in the C4 and CAM pathways were identified. These findings provide a new species in which C4 and CAM co-occur and raises the question if this phenomenon is indeed so rare or just hard to detect and probably more common in succulent C4 lineages. HighlightC4 and CAM metabolism co-occur in the C4-like species Sesuvium sesuvioides (Aizoaceae).

plant biology↗

bioRxiv2021

Insights into regulation of C2 and C4 photosynthesis in Amaranthaceae/Chenopodiaceae using RNA-Seq

Amaranthaceae (incl. Chenopodiaceae) show an immense diversity of C4 syndromes. More than 15 independent origins of C4 photosynthesis, partly in halophytic and/or succulent lineages, and the largest number of C4 species in eudicots signify the importance of this angiosperm lineage in C4 evolution. Here, we conduct RNA-Seq followed by comparative transcriptome analysis of three species from Camphorosmeae representing related clades with different photosynthetic types: Threlkeldia diffusa (C3), Sedobassia sedoides (C2), and Bassia prostrata (C4). Results show that B. prostrata belongs to the NADP-ME type and core genes encoding for C4 cycle are significantly up-regulated when compared to Sed. sedoides and T. diffusa, Sedobassia sedoides and B. prostrata share a number of up-regulated C4-related genes, however, two C4 transporters (DIT and TPT) are found significantly up-regulated only in Sed. sedoides. Combined analysis of transcription factors (TFs) of the closely related lineages (Camphorosmeae and Salsoleae) revealed that no C3 specific TFs is higher in C2 species as compared to C4 species, instead the C2 species show their own set of up-regulated TFs. Taken together, our study indicates that the hypothesis of the C2 photosynthesis as a proxy towards C4 photosynthesis is questionable in Sed. sedoides and more in favour of an independent evolutionary stable-state. HighlightTranscript expression profiles of C2 species are distinct and best explained as representing an independent evolutionary stable state.

plant biology↗

bioRxiv2021

Transcriptome sequence reveals candidate genes involving in the post-harvest hardening of trifoliate yam Dioscorea dumetorum

Storage ability of D. dumetorum is restricted by a severe phenomenon of post-harvest hardening which starts 72h after harvest and renders tubers inedible. Previous work has only focused on the biochemistry changes affecting the PHH on D. dumetorum. To the best of our knowledge nobody has identified candidate genes responsible for hardness on D. dumetorum. Here, transcriptome analysis of D. dumetorum tubers was performed, 4 months after emergence (4MAE), after harvest (AH), 3 days AH (3DAH) and 14 days AH (14DAH) on four accessions using RNA-Seq. In total between AH and 3DAH, 165, 199,128 and 61 differentially expressed genes (DEGs) were detected in Bayangam 2, Fonkouankem 1, Bangou 1 and Ibo sweet 3 respectively. Functional analysis of DEGs revealed that genes encoding for cellulose synthase A, xylan O-acetyltransferase chlorophyll a/b binding protein 1,2,3,4 and transcription factor MYBP were found predominantly and significantly up-regulated 3DAH, implying that genes were potentially involved in the post-harvest hardening. A hypothetical mechanism of this phenomenon and its regulation has been proposed. These findings provide the first comprehensive insights into genes expression in yam tubers after harvest and valuable information for molecular breeding against the post-harvest hardening. A hypothetical mechanism of this phenomenon and its regulation has been proposed. These findings provide the first comprehensive insights into genes expression in yam tubers after harvest and valuable information for molecular breeding against the post-harvest hardening.

plant biology↗

bioRxiv2020

High contiguity de novo genome sequence assembly of Trifoliate yam (Dioscorea dumetorum) using long read sequencing

Trifoliate yam (Dioscorea dumetorum) is one example of an orphan crop, not traded internationally. Post-harvest hardening of the tubers of this species starts within 24 hours after harvesting and renders the tubers inedible. Genomic resources are required for D. dumetorum to improve breeding for non-hardening varieties as well as for other traits. We sequenced the D. dumetorum genome and generated the corresponding annotation. The two haplophases of this highly heterozygous genome were separated to a large extent. The assembly represents 485 Mbp of the genome with an N50 of over 3.2 Mbp. A total of 35,269 protein-encoding gene models as well as 9,941 non-coding RNA genes were predicted and functional annotations were assigned.

genomics↗