Abstract: In order to improve rices nitrogen absorption rate, marker\|free, reporter\|free and backbone\|free transgenic rice, (Nitrate Transporter, NAT) was cloned from diatom genome, and three plant expression vectors were constructed: marker-free plant expressing vector pANW2300K-which makes it possible for diatom nitrate transporter-NAT gene to be highly expressed in rice, positive-negative plant expressing vector pCodA1301 which carries a negative selectable marker-CodA and the plant expressing vector pIpt121. Through these vectors we proved that Ipt gene can inhibit the growth of tobacco, while having little effect on rice. We also established a transgenic system based on transient selection and positive-negative selection. Eighteen marker-free and backbone-free rice plants expressing the target gene NAT were identified to be transgenic, representing a transformation rate of 28%. It is the first time in China that intragenesis technology was fully used in rice．

Key words: rice, intragenesis technology, transient selection, positive-negative selection, NAT