Chitosan stimulates root hair callose deposition, endomembrane dynamics, and inhibits root hair growth

The study examines the effects of chitosan on root hair (RH) growth and callose deposition in Arabidopsis thaliana, revealing that low concentrations (0.001%) induce callose deposition without inhibiting primary root growth, while high concentrations (0.01%) significantly inhibit RH growth and alter endomembrane dynamics. The callose deposition is dependent on the PMR4 gene, but RH growth inhibition occurs independently of callose deposition. High chitosan concentrations trigger more intense calcium spiking, MAPK activation, and changes in 8,507 genes, compared to only 58 genes affected by low concentrations. The research suggests that chitosan acts as an elicitor with concentration-dependent effects, highlighting its potential as a modulator of plant growth and defense mechanisms.