Involvement of reactive oxygen species in zinc-deficiency induced inhibition of crown root growth in maize plant

The levels of reactive oxygen species (ROS) including superoxide anion radical (O₂^•−), hydrogen peroxide (H₂O₂) increase in plants under Zinc (Zn) deficiency stress. However, less is known about whether excessive levels of ROS mediate root development and growth under Zn deficient condition.

Maize variety Zhengdan 958 was chosen to grow with nutrient solution culture with the treatments (DAT) of 0 and 1 μM Zn supply. Exogenous H₂O₂ and its scavenger (N, N-dimethylthiourea, DMTU), and a catalase inhibitor (Aminotriazole, AT) were added. The distribution of ROS in roots were detected by chemical staining and fluorescent probe technology. The differential expression of related genes and proteins in roots were analyzed through proteomics and transcriptomics approaches.

Zn deficiency stress caused high O₂^•−and H₂O₂ levels in roots and decreased crown root elongation. Exogenous addition of DMTU reduced the H₂O₂ content in roots and the inhibitory effect of Zn deficiency on root elongation. Under Zn supply, the addition of H₂O₂ and AT resulted in short crown roots. The down-regulation of several genes associated with cell wall extension, such as cellulose synthase, xyloglucan endtransglucosylase/hydrolase and beta expansin 8, were found in the transcriptome and proteome data of Zn-deficient root.

It is suggested that H₂O₂ might be involve in the inhibition of crown root development in maize plants subjected to Zn deficiency stress, which may account for the down-regulation of genes related to cell wall extension through transcriptomic and proteomic analysis.