Nitrogen supply affects ion homeostasis by modifying root Casparian strip formation through the miR528-LAC3 module in maize
Yu Guo, Yafei Wang, Huan Chen, Qingguo Du, Zhonghua Wang, Xiaoping Gong, Qing Sun, Wenxue Li
Abstract
Although nitrogen (N) is known to affect mineral element homeostasis in plants, the molecular mechanisms of interactions between N and other nutrients remain largely unclear. We report here that N supply affects ion homeostasis of maize. Berberine hemisulphate staining and a propidium iodide penetration assay showed that N luxury significantly delayed Casparian strip (CS) formation in maize roots. We further demonstrated that N-mediated CS formation of maize was independent of RBOHF-activated H2O2 production. N luxury induced the expression of ZmmiR528 in whole root and root tips. Knock-down and loss-of-function ZmmiR528 promoted CS formation under both N-luxury and N-deficient conditions. Both ZmMIR528a and ZmMIR528b contribute to the early CS formation under different N conditions. RNA-seq and real-time RT-PCR analysis demonstrated that ZmLAC3, but not ZmLAC5 responded to N treatments. Consistent with results obtained with ZmmiR528 TM transgenic maize and mir528a/b loss-of-function mutants, transgenic maize overexpressing ZmLAC3 displayed early CS formation under different N conditions. In field condition, the K, Ca, Mn, Cu, Mg and Zn concentrations were greater in the ear leaf of ZmLAC3 overexpressing transgenic maize than in the WT. The results indicate that ZmmiR528 affects CS formation of maize by regulating the expression of ZmLAC3 and modification of CS formation has the potential to improve maize quality.