Auxin promotes chloroplast division by increasing the expression of chloroplast division genes.

Key message: Auxin stimulates chloroplast division by upregulating the expression of genes involved in chloroplast division and influencing the positioning of chloroplast division rings. Chloroplasts divide by binary fission, forming a ring complex at the division site. Auxin, particularly indole acetic acid (IAA), significantly influences various aspects of plant growth. However, the impact of auxin on chloroplast division remains unclear. In this study, different concentrations of exogenous IAA were applied to wild Arabidopsis thaliana. The results showed that the number and size differences of chloroplasts in the cells of Arabidopsis thaliana treated with high concentrations of IAA increased compared to untreated plants. Further investigation revealed that high concentrations of IAA affected the expression of chloroplast division genes and the formation of division rings. In chloroplast division mutants, the effect of IAA on promoting chloroplast division is impaired. Defects of IAA synthetic gene also lead to a reduced effect of IAA on chloroplast division. Our findings demonstrate that auxin influences chloroplast division by regulating the expressions of chloroplast division genes and affecting the localization of division rings. These results are significant for further exploring the relationship between auxin and chloroplast division.