A nitrate transporter encoded by ZmNPF7.9 is essential for maize seed development

•ZmNPF7.9 is specifically expressed in the basal endosperm transfer layer cells of maize endosperm.•ZmNPF7.9 is a low-affinity, pH-dependent bidirectional nitrate transporter.•ZmNPF7.9 plays a specific role in seed development and grain weight by regulating nitrate transport and nutrition metabolism.