Abscisic acid alleviates iron deficiency by promoting root iron reutilization and transport from root to shoot in A rabidopsis

Abscisic acid ( ABA ) has been demonstrated to be involved in iron ( F e) homeostasis, but the underlying mechanism is largely unknown. Here, we found that F e deficiency induced ABA accumulation rapidly (within 6 h) in the roots of A rabidopsis . Exogenous ABA at 0.5  μ M decreased the amount of root apoplastic F e bound to pectin and hemicellulose, and increased the shoot F e content significantly, thus alleviating F e deficiency‐induced chlorosis. Exogenous ABA promoted the secretion of phenolics to release apoplastic F e and up‐regulated the expression of AtNRAMP3 to enhance reutilization of F e stored in the vacuoles, leading to a higher level of soluble F e and lower ferric–chelate reductase ( FCR ) activity in roots. Treatment with ABA also led to increased F e concentrations in the xylem sap, partially because of the up‐regulation of AtFRD3 , AtYSL2 and AtNAS1 , genes related to long‐distance transport of F e. Exogenous ABA could not alleviate the chlorosis of abi5 mutant resulting from the significantly low expression of AtYSL2 and low transport of F e from root to shoot. Taken together, our data support the conclusion that ABA is involved in the reutilization and transport of F e from root to shoot under F e deficiency conditions in A rabidopsis .