Cluster of genes related to storage protein synthesis,specifically genes encoding proteins of the prolamin class show upregulation in the XAPendosperm. Subsequently, mature grains analysis indicates that XAP grains have increasedpercentages of total nitrogen and prolamins. These findings suggest that synthesis of prolaminstorage protein might be stimulated in XAP endosperm. The expression of metal transportergenes including Zn and Fe transporters were upregulated in XAP endosperm. Correspondingly,genes related to the biosynthesis of nitrogen chelator compounds like nicotianamine synthaseare upregulated in the XAP endosperm. Consistent with this result, significant increment of Znand Fe was observed in mature XAP grains. The availability of N assimilates in XAP endospermobviously enhances the biosynthesis of nitrogenous chelator compounds and metaltransporters, which might accelerate the uploading of Zn and Fe into the developing grain.