Developmental robustness of the shoot apical meristem despite sex-chromosome dosage imbalance in Silene latifolia.

backgroundMaintaining developmental stability despite sex-linked gene dosage imbalance represents a fundamental challenge for dioecious species. In the dioecious plant Silene latifolia, floral sexual dimorphism is associated with the sex-linked WUSCHEL (SlWUS1) and a CLAVATA3-like gene (GSFY) resulting in sex-specific differences in WUS-CLV3 copy number. Because the WUS-CLV3 feedback loop is a central regulator of stem cell homeostasis in the shoot apical meristem (SAM), such dosage imbalance would be expected to destabilise meristem maintenance.

resultsWe performed a quantitative analysis of SAM size in male and female Silene latifolia plants across vegetative developmental stages. Seedlings were grown in liquid half-strength Murashige and Skoog (½ MS) medium, and SAM morphology was examined using differential interference contrast microscopy. SAM diameter and area were subsequently measured using ImageJ. SAM size did not differ between male and female plants throughout vegetative development, despite differences in WUS copy number. This robustness persisted following exogenous application of the GSFY peptide (GSFYp) and cytokinin (CK), both of which significantly modulated SAM size and WUS expression. Expression analyses showed that the X-linked SlWUS1 is weakly expressed in the SAM, whereas the autosomal SlWUS2 exhibits high and sex-independent expression and responds similarly to peptide and CK signals in both sexes.

conclusionsThese findings indicate that stem cell homeostasis in S. latifolia is primarily maintained by the autosomal SlWUS2, which buffers sex-linked dosage variation without relying on classical gene dosage compensation. Our results suggest the presence of a regulatory architecture that protects essential developmental processes from destabilisation during the evolution of dioecy.