Cadmium affects cell niches maintenance in Arabidopsis thaliana post-embryonic shoot and root apical meristem by altering the expression of WUS/WOX homolog genes and cytokinin accumulation

Cadmium (Cd) is one of the most widespread polluting heavy metals in both terrestrial and aquatic environments and represents an extremely significant pollutant causing severe environmental and social problems due to its high toxicity and large solubility in water. In plants, the root is the first organ that get in contact with Cd. It is absorbed by the root system and translocated to the shoot and leaves through xylem loading, causing a variety of genetic, biochemical, and physiological damages. Cd inhibits both the root and shoot growth, but the mechanisms underlying this inhibition remain elusive. In this context in the present work we focused the attention on the effects of Cd on meristem size and organization of both shoot and root. To this aim morpho-histological and molecular analyses were carried out on 5 days old seedlings exposed or not to Cd (100 μM and 150 μM for 24) of wild type and transgenic lines expressing molecular markers with an important role in shoot and root pattern organization. More precisely, we monitored the expression pattern of WUS/CLV3 and WOX5 transcription factors involved in the establishment and maintenance of stem cell niche and the control of meristem size and of TCSn::GFP cytokinin-sensitive sensor as relevant components of hormone circuit controlling shoot and root growth. The results highlighted that the treatments with Cd impacts shoot and root size and shape by altering the paralogous WOX genes expression via cytokinin accumulation.