Early Ovule Morphogenesis and Germ Cells Formation

AUTRAN, DAPHNÉ; MOSCA, GABRIELA; FREY, A; HAMANT O; GRIMANELLI G ; LARTAUD, M; BAROUX, CELIA; MENDOCILLA SATO; GIRALDO-FONSECA, A; GODIN, C ; DELGADO LUCIANA; HERNANDEZ-LAGANA, ELVIRA; PIRES, N ; GROSSNIKLAUS, ULRICH; BOUDAOUD, A ; CONEJERO, G

Workshop; Proceedings of the 7th Series of Seminars on Advances in Apomixis Research; 2020

In flowering sexual plants, the female germline precursor differentiates as a singlespore mother cell, so-called Megaspore Mother Cell (MMC). MMC formation is contemporaryto early ovule primordium growth. Here, we explored how organ growthcontributes to MMC differentiation. In the model plant Arabidopsis, by quantitative analysisof 3D images at cellular resolution, cell cycle markers, and tissue growth models,we identified spatio-temporal patterns of cell growth and divisions in the early ovuleprimordium. Our analysis revealed that MMC characteristics first arise in more thanone cell, but MMC fate becomes progressively restricted to a single cell during organgrowth. Altered primordium growth patterns in katanin mutants?affected in microtubulesdynamics?coincided with a delay in theMMCfate restriction process. We propose a modelof gradual canalization of reproductive cell fate coupled to ovule primordium growth inArabidopsis. Further studies should determine if this model is conserved in ovules ofgrasses; either sexual such as in maize, or following an aposporous reproductive mode,such as in Paspalum.