Abstract
Four NRT2 genes encoding nitrate uptake in rice (Oryza sativa L. cv Nipponbare) were extracted from the rice genome database. NRT2.1 and NRT2.2 have same ORF sequence. NRT2.3 and NRT2.4 show 46.3% similarity. In this study, relationships between NRT2s expression and nitrate uptake are discussed.
To investigate time course expressions of NRT2s with RT-PCR method, rice seedlings, which had been pretreated with CaSO4 solution with or without (NH4)2SO4, were soaked in KNO3 solution. Transcriptions of NRT2.1, NRT2.2 and NRT2.4 were induced by NO3- and delayed transcriptions were found in NRT2.1 and NRT2.4 by NH4+ pretreatment. However, NRT2.3 was expressed constitutively.
Nitrate uptake was also induced by NO3- within 1 hour. The induction time was delayed 1 to 2 hours by NH4+ pretreatment compared to that without NH4+. This result is similar to the transcription pattern of NRT2.1, suggesting that NRT2.1 plays an important role in nitrate uptake in roots.
