Biology subjects

Adema, K.

Publications and source records attributed to Adema, K..

3 recordsLinked to original sources

bioRxiv2026

Spatiotemporal dynamics of ethylene biosynthesis shape infection and nodule initiation in Medicago truncatula

Ethylene is a well-established negative regulator of nodulation, yet how ethylene biosynthesis and perception are spatially coordinated during early symbiotic signalling remains unresolved. Here, we investigate the dynamics of ethylene responses in Medicago truncatula using transcriptomics, promoter-reporter analyses, loss-of-function approaches and a synthetic reporter. We show that the activity of the ethylene-responsive EBSn reporter shifts from inner root tissues under non-symbiotic conditions to the outer cortex and epidermis following rhizobial inoculation, revealing a spatial reprogramming of ethylene signalling. Among the eight Medicago 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID SYNTHASE (ACS) genes, upon rhizobia application MtACS3 is induced in outer root cell layers, while MtACS10 is repressed in the inner cortex and pericycle, mirroring the shift in ethylene perception. Functional analysis demonstrates that MtACS10 restricts nodule initiation, whereas MtACS3 modulates infection thread number, prevents nodule clustering, and contributes to radial positioning of nodule primordia. Rhizobial induced ectopic ACS expression in the root interior counteracts MtACS10 repression and blocks nodulation, highlighting the requirement for spatially confined downregulation of ethylene biosynthesis. Together, these findings establish a framework in which localized shift in ethylene biosynthesis, mediated by distinct Medicago ACS genes, balances infection and organogenesis while co-defining the spatial limits of the root susceptible zone.

plant biology↗

bioRxiv2025

A PLETHORA transcription factor shapes cucumber shoot architecture

O_LIPLETHORA transcription factors (PLTs) are master regulators of plant development. Loss of shoot meristematic PLTs leads to reduced phyllotactic regularity and robustness in Arabidopsis and increased inflorescence branching in tomato. Whether these factors have similar functions in other species is not known. C_LIO_LITo address this knowledge gap, we integrated phylogenetic, transcriptomic, and genome-wide in vitro binding strategies with quantitative shoot architecture phenotyping of a panel of cucumber TILLING mutants of each CsPLT homolog. C_LIO_LIWe determined that CsPLT3/7 and CsPLT are expressed in complementary domains in the cucumber shoot apex. DAP-seq data indicated that both transcription factors recognised an ANT-like consensus motif and bound to SAM organising genes. We identified strong phenotypic defects in multiple Csplt3/7 mutants. In mature seeds, Csplt3/7 mutants formed a flat apex instead of a shoot apical meristem, from which secondary meristems emerged during subsequent seedling development. Mature Csplt3/7 shoots exhibited defects in internode length regularity, stem architecture, flower morphology, and axillary organ initiation. Moreover, phyllotactic patterns were slightly shifted from a spiral towards a distichous orientation. C_LIO_LIWe present one of the first pieces of evidence that the PLT3/7 clade fulfils both conserved and diversified roles in shoot development across taxonomic family boundaries. C_LI

plant biology↗

bioRxiv2023

Crane fly semiochemical overrules coordinate cyanobiont differentiation in Azolla ferns

Semiochemicals from insects that restrict plant symbiont dinitrogen fixation had not been known. Here we report on a the glycosylated triketide {delta}-lactone only found in Nephrotoma cornicina crane flies, cornicinine, that causes chlorosis in the floating-fern symbioses from the genus Azolla. Cornicinine was chemically synthesized, as well as its aglycone and diastereoisomer. Only the glycosylated trans-A form was active: 500 nM cornicinine in the growth medium turned the dinitrogen-fixing cyanobacterial filaments from Nostoc azollae inside the host leaf cavities into akinete-like cells. Cornicinine further inhibited akinete germination in Azolla sporelings, precluding re-establishment of the symbiosis during sexual reproduction. It did not affect the plant Arabidopsis thaliana or several free-living cyanobacteria from the genera Anabaena or Nostoc. Chlorosis occurred in hosts on nitrogen with and devoid of cyanobiont. Cornicinine, therefore, targeted host mechanisms resulting in coordinate cyanobiont differentiation. Sequence profiling of messenger RNA from isolated leaf cavities confirmed high NH4-assimilation and proanthocyanidin biosynthesis in this trichome-rich tissue. Leaf-cavity transcripts in ferns grown on cornicinine reflected activation of Cullin-RING ubiquitin-ligase pathways, known to mediate metabolite signaling and plant elicitation consistent with the chlorosis phenotype. Transcripts accumulating when akinetes are induced, in leaf cavities of ferns on cornicinine and in megasporocarps, were consistent with increased JA-oxidase, sulfate transport and exosome formation. The work begins to uncover molecular mechanisms of cyanobiont differentiation in a seed-free plant symbiosis important for wetland ecology or circular crop-production today, that once caused massive CO2 draw-down during the Eocene geological past. SignificanceCoordinated differentiation of host and filamentous cyanobacteria underlies the development of ecologically important symbioses; this includes the floating ferns Azolla which share their wetland habitat with Nephrotoma cornicina craneflies containing the glycosylated triketide {delta}-lactone semiochemical, cornicinine. Cornicinine overrules cyanobiont differentiation thus inhibiting symbiosis N2-fixation and sexual reproduction; its mode of action resembles plant elicitation as suggested by transcriptional profiling of cells lining the cyanobiont cavities using a new release of the fern host genome.

plant biology↗