A reduced aquatic angiosperm lacking canonical gravitropism genes retains robust gravity- responsive transcriptional programs
Year: 2026
Type: preprint
Abstract: Gravitropism is the ability of plants to sense and respond to gravity, a fundamental trait ensuring proper orientation of roots and shoots. While well-characterised in terrestrial plants, how aquatic species respond to altered gravity remains unknown. Wolffia australiana , one of the smallest known flowering plants, is morphologically reduced, rootless, and fast-growing, making it an ideal model for studying plant adaptation under extreme space-like conditions. We examined W. australiana 's growth, morphology, and transcriptomic responses under different gravity levels (µg, 0.16g, 2g and 4g) using random positioning machines and a large-diameter centrifuge. Lunar gravity increased growth rate, while hypergravity suppressed it. Morphological changes in mother fronds were observed only under hypergravity. Transcriptomic profiling revealed that ~ 25% of genes were differentially expressed under low gravity, compared to ~ 7% under 2g and ~ 11% under 4g. Despite lacking canonical gravity-sensing genes, W. australiana exhibited distinct and coordinated transcriptional responses across treatments. Notably, circadian clock genes and those with time-of-day (TOD)-dependent expression were significantly overrepresented among gravity-responsive genes; many of these were enriched in the epidermis. These findings highlight W. australiana 's unique transcriptional and morphological plasticity, suggesting alternative gravitropic mechanisms with direct implications for space agriculture.
Source: Research Square
Language: English
Subfield: Physiology
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W7202176230