Rice grown under anaerobic waterlogged soil condition takes up ammonium as a major source of nitrogen (N). A substantial quantity of nitrate is taken up by rice when aeration conditions prevail. This work compared the physiological and molecular responses of N-depleted rice (Oryza sativa L. japonica ssp. cv. Wuyunjing) to re-supply of different N sources in a hydroponic system. Expression of six genes known to be related to N uptake and assimilation in roots was analyzed by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). N starvation increased root growth but decreased shoot biomass and nitrate reductase (NR) activity. In comparison to nitrate as N source, ammonium tended to inhibit root growth but significantly improved shoot growth, total N uptake, and, particularly, the translocation of N to the above ground parts. Replacing half of the ammonium by nitrate in the single ammonium solution increased glutamine synthetase (GS) activity and total N uptake. This replacement enhanced expression of OsAMT1;3 but decreased the expression of OsAMT1;2 in the roots. Likewise, replacing half of the nitrate by ammonium in the single nitrate solution, increased NR activity and expression of an NR gene (OsNR1) but suppressed expression of OsNRT2 in the roots. Expression of both OsAMT1;1 and a GS gene (OsGS1;1) was relatively constant and not affected by the N form or starvation in the rice roots. Predominant beneficial effects of dual supply of the two forms of N in comparison with a single form of N either as ammonium or as nitrate might be due to improvement of ammonium uptake due to nitrate presence near the roots and enhanced reduction of nitrate in leaves by ammonium.

Here, orthologous genes of six phosphate transporter (PiT) genes, which are members of the Pht1 and Pht2 families in tomato and potato, have been cloned from the solanaceous species pepper, eggplant and tobacco. Overall, expressions of these genes in pepper, eggplant and tobacco showed similar patterns to those in tomato and potato: P-starvation enhancement in both leaves and roots for Pht1; 1, P-depletion induction exclusively in roots for Pht1; 2, mycorrhizal enhancement for Pht1; 3, and mycorrhizal induction for both Pht1; 4 and Pht1; 5. In the roots of nonmycorrhizal eggplant, SmPht1; 3, SmPht1; 4 and SmPht1; 5 were also expressed under extreme P starvation. Mycorrhizal symbiosis under high-P supply conditions reduced plant growth, with concurrent enhancement of Pht1; 2 expression in the roots of pepper as well as eggplant. In addition, the mycorrhizal symbiosis down-regulated the expression of Pht2; 1 genes greatly in the leaves of pepper and tobacco. The discrepancies between the evolutionary distances of the PiT genes and their expression patterns among the five species suggest greater complexity in function of PiT in plants than previously expected.

采用实时荧光定量PCR技术，通过使用特异引物，对水稻中的低丰度表达基因Osamt1；3进行了转录水平上的定量分析，成功建立了可检测低丰度表达基因的SYBRGreen实时荧光定量PCR技术平台。该方法具有很好的准确性和实用性。获得的荧光定量PCR扩增曲线，基线平整，指数区明显，斜率大且固定；线性范围广，17～36个循环都能测出；稳定性、重复性好，变异系数仅为0.47%；标准曲线表明，循环闽值与PCR体系中起始模板量的对数值之间有着良好的线性关系，可对基因表达进行相对定量；缺氯条件下OSAMTI；3与纯NH4+处理相比表达量增加4倍以上。