LAUSR

The polarized and dynamic actin cytoskeleton is essential for root cell growth. Here, we report the key role of thiol‐disulfide oxidoreductase PDI1;1 in actin structures. Microscopic analyses revealed that after Oryza sativa roots were exposed to H2O2, both actin and PDI1;1 were depolarized and arranged in a meshwork. In H2O2‐exposed cells, actin formed intermolecularly disulfide‐bonded high‐molecular‐weight structures, which were thiol‐trapped by PDI1;1. Recombinant PDI1;1 exhibited the ability to recognize actin in an in vitro binding assay. During recovery from H2O2 exposure, the amount of disulfide‐bonded high‐molecular‐weight structures of actin decreased over time, but deficiency of PDI1;1 inhibited the decrease. These results suggest a PDI1;1‐dependent pathway that reduces disulfide bonds in high‐molecular‐weight structures of actin, thus promoting their degradation.