OSense O-Sense


期刊:Plant Physiology
标题:A Transcription Factor, OsMADS57, Regulates Long-distance Nitrate Transport and Root Elongation
NO3-流实验处理方法:0.2 mM NO3-培养2周后,N饥饿处理3天
NO3-流实验测试液成份:0.2 mM KNO3, 0.2 mM CaCl2, 0.1 mM NaCl, 0.1 mM MgSO4, 0.3 mM MES, pH 6.0


Root nitrate uptake adjusts tothe plant’s nitrogen demand for growth. Here, we report that OsMADS57, aMADS-box transcription factor, modulates nitrate translocation from rice (Oryzasativa) roots to shoots under low-nitrate conditions. OsMADS57 is abundantlyexpressed in xylem parenchyma cells of root stele and is induced by nitrate.Compared with wild-type rice plants supplied with 0.2 mM nitrate, osmads57mutants had 31% less xylem loading of nitrate, while overexpression lines had2-fold higher levels. Shoot-root 15N content ratios were 40% lower in themutants and 76% higher in the overexpression lines. Rapid NO3− root influxexperiments showed that mutation of OsMADS57 did not affect root nitrateuptake.

Reverse transcriptionquantitative PCR analysis of OsNRT2 nitrate transporter genes showed that after5 min in 0.2 mM nitrate, only OsNRT2.3a (a vascular-specific high-affinitynitrate transporter) had reduced (by two-thirds) expression levels. At 60 minof nitrate treatment, lower expression levels were also observed for threeadditional NRT2 genes (OsNRT2.1/2.2/2.4). Conversely, in the overexpressionlines, four NRT2 genes had much higher expression profiles at all time pointstested.

As previously reported, OsNRT2.3afunctions in nitrate translocation, indicating the possible interaction betweenOsMADS57 and OsNRT2.3a. Yeast one-hybrid and transient expression assaysdemonstrated that OsMADS57 binds to the CArG motif (CATTTTATAG) within theOsNRT2.3a promoter. Moreover, seminal root elongation was inhibited in osmads57mutants, which may be associated with higher auxin levels in and auxin polartransport to root tips of mutant plants. Taken together, these results suggestthat OsMADS57 has a role in regulating nitrate translocation from root to shootvia OsNRT2.3a.



根硝酸盐吸收可调节植物对氮的生长需求。在这里,我们报告OsMADS57,一种MADS-box转录因子,在低硝酸盐条件下调节从水稻(Oryza sativa)根到芽的硝酸盐易位。OsMADS57在根茎的木质部薄壁细胞中大量表达,并由硝酸盐诱导。与提供0.2mM硝酸盐的野生型水稻植物相比,osmads57突变体的硝酸盐木质部负载量减少31%,而过表达株系的水平增加2倍。芽根15N含量比率在突变体中低40%,在过表达株系中高76%。快速NO3-根流入实验表明,OsMADS57的突变不影响硝酸根的吸收。

OsNRT2硝酸盐转运蛋白基因的逆转录定量PCR分析显示,在0.2mM硝酸盐中5分钟后,仅OsNRT2.3a(血管特异性高亲和力硝酸盐转运蛋白)表达水平降低(三分之二)。在硝酸盐处理60分钟时,还观察到另外三种NRT2基因(OsNRT2.1 / 2.2 / 2.4)的较低表达水平。相反,在过表达株系中,四个NRT2基因在所有测试时间点具有高得多的表达谱。


Figure 3. NO3- acquisition in wild-type (WT), mutants (m1-2) and overexpression lines (Ox1-3). Rice seedlings were grown in IRRI nutrient solution containing 0.2 mM NO3- for 2 weeks and then deprived of N for 3 d. The plants were transferred to IRRI nutrient solution containing 0.2 mM 15NO3- for 5 min. (B) Net NO3- fluxes in the seminal root meristem of rice plants supplied with 0.2 mM NO3- for 11 min. (C) Mean rate of NO3- fluxes during the entire 11 min. Data are means of five replications ± SE. *, P < 0.05 (Student’s t-test) comparing the WT and other lines. min = minutes.