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PP：南農資環院丨MADS-box轉錄因子促低氮時根系吸硝
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期刊：Plant Physiology
主題：MADS-box轉錄因子促低氮時根系吸硝
標題：A Transcription Factor, OsMADS57, Regulates Long-distance Nitrate Transport and Root Elongation
影響因子：6.305
檢測指標：NO3-流速
NO3-流實驗處理方法：
0.2 mM NO3-培養2周后，N饑餓處理3天
NO3-流實驗測試液成份：
0.2 mM KNO3, 0.2 mM CaCl2, 0.1 mM NaCl, 0.1 mM MgSO4, 0.3 mM MES, pH 6.0
作者：南京農業大學張亞麗、黃雙杰
英文摘要
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.
中文摘要（谷歌機翻）
根硝酸鹽吸收可調節植物對氮的生長需求。在這里，我們報告OsMADS57，一種MADS-box轉錄因子，在低硝酸鹽條件下調節從水稻（Oryza sativa）根到芽的硝酸鹽易位。OsMADS57在根莖的木質部薄壁細胞中大量表達，并由硝酸鹽誘導。與提供0.2mM硝酸鹽的野生型水稻植物相比，osmads57突變體的硝酸鹽木質部負載量減少31％，而過表達株系的水平增加2倍。芽根15N含量比率在突變體中低40％，在過表達株系中高76％。快速NO3-根流入實驗表明，OsMADS57的突變不影響硝酸根的吸收。
OsNRT2硝酸鹽轉運蛋白基因的逆轉錄定量PCR分析顯示，在0.2mM硝酸鹽中5分鐘后，僅OsNRT2.3a（血管特異性高親和力硝酸鹽轉運蛋白）表達水平降低（三分之二）。在硝酸鹽處理60分鐘時，還觀察到另外三種NRT2基因（OsNRT2.1 / 2.2 / 2.4）的較低表達水平。相反，在過表達株系中，四個NRT2基因在所有測試時間點具有高得多的表達譜。
如先前報道，OsNRT2.3a在硝酸鹽易位中起作用，表明OsMADS57和OsNRT2.3a之間可能的相互作用。酵母單雜交和瞬時表達測定證明OsMADS57與OsNRT2.3a啟動子內的CArG基序（CATTTTATAG）結合。此外，osmads57突變體中的精液根伸長受到抑制，這可能與突變植物根尖中的生長素水平和生長素極性轉運相關。總之，這些結果表明OsMADS57通過OsNRT2.3a調節從根到莖的硝酸鹽易位。
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 15 NO3- 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.