Biology subjects

Rambaud-Lavigne, L.

Publications and source records attributed to Rambaud-Lavigne, L..

2 recordsLinked to original sources

bioRxiv2023

Chimeric identities and reduced stiffness characterise the shoot apex of Arabidopsis stem cell mutants

Stem cell homeostasis in the shoot apical meristem involves a core regulatory feedback loop between the signalling peptide CLAVATA3, produced in stem cells, and the transcription factor WUSCHEL, expressed in the underlying organising centre. clavata mutants display massive meristem overgrowth, which is thought to be caused by stem cell overproliferation, although it is unknown how uncontrolled stem cell divisions lead to this altered morphology. Here we first reveal local buckling defects in mutant meristems, and use analytical models to show how mechanical properties and growth rates may contribute to the phenotype. Indeed, clavata meristems are mechanically more heterogeneous than the wild type, and also display regional growth heterogeneities. Furthermore, stereotypical wild-type meristem organisation is lost in mutants, in which cells simultaneously express distinct fate markers. Finally, cells in mutant meristems are auxin responsive, suggesting that they are functionally different from wild-type stem cells. Thus all benchmarks show that clavata meristem cells are different from wild-type stem cells, suggesting that fasciation is caused by the disruption of a more complex regulatory framework that maintains distinct genetic and functional domains at the shoot apex. Summary statementHeterogeneities in cell mechanics, growth, function and identity contribute to buckling in clavata mutant shoot apices.

plant biology↗

bioRxiv2021

INDEHISCENT regulates explosive seed dispersal

How traits evolve to produce novelty or stasis is an open question in biology. We investigate this question in Cardamine hirsuta, a relative of Arabidopsis thaliana that employs explosive fracture to disperse its seeds. This trait evolved through key morphomechanical innovations that distinguish the otherwise very similar, dehiscent fruit of these two species. Using CRISPR/Cas9, we show that dehiscence zone formation is absolutely required for explosive fracture in C. hirsuta, and is controlled by the bHLH transcription factor INDEHISCENT (IND). Using mutant screens, we identified the MADS-box transcription factor FRUITFULL (FUL) as a negative regulator of IND in C. hirsuta. Although FUL function is conserved in C. hirsuta, the consequences of IND mis-expression differ in ful mutants of C. hirsuta versus A. thaliana. In ful mutants of both species, valve tissue is replaced by dehiscence zone tissue, which comprises two distinct cell types: lignified layer and separation layer cells. While A. thaliana ful mutants develop stunted fruit with ectopic lignified layer cells, C. hirsuta ful mutants have elongated fruit with ectopic separation layer cells. We show that IND dose determines the proportion of these two cell types in ectopic dehiscence zones. We also show that the extent of ectopic lignification caused by IND mis-expression determines fruit length. Our findings indicate developmental system drift in the conserved gene network patterning dehiscent fruit in two related Brassicaceae species.

plant biology↗