Os06g0706400

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OsPTR9 affects nitrogen utilization efficiency, growth and grain yield in rice. [1]

Annotated Information

Function

The effect of OsPTR9 on the formation of roots. (from reference [1]).

OsPTR9 expression is regulated by light and N source

OsPTR9 is closely related to the functional di/tripeptide transporters [2] and is localized at the plasma membrane. Members of the PTR/NRT1 family transport a wide range of substrates, including di/tripeptides, nitrate, histidine, carboxylates, other N-containing compounds such as IAA-amino acid conjugates, ABA, glutathione, and even the defence compound glucosinolate, and other substrate compounds might be identified [3][4][5][6][7][2]. OsPTR9 was found to be expressed in all organs analysed, but expression levels varied. The expression of OsPTR9 was high at night and low during the light period, which is different than the expression patterns of many ammonium and nitrate transporter genes [8][9]. Inorganic N is usually used for metabolic synthesis in Arabidopsis under light, but organic N is usually used for long-distance transport and substance storage under dark conditions [10]. Therefore, OsPTR9 might also be an organic N transporter. Similar to AMT1;3 [11], but different from other inorganic N transporters, OsPTR9 expression also affected root growth. The expression of OsPTR9 was repressed during N starvation and induced by ammonium, similar to the expression induction of the ammonium transporter OsAMT1;2 [12]. The regulation of OsPTR9-expression by N sources and light/dark changes shows that there are common feedback regulatory pathways for C/N balance in rice, similar to reports from studies of Arabidopsis [13][14].

Root architecture is affected by altered expression of OsPTR9. (from reference [1]).

The effect of OsPTR9 on the development of roots and stems may contribute to nutrient uptake and allocation

Biomass and photosynthesis rate differed most between altered-OsPTR9 expressing plants and the wild type, when ammonium or nitrate was the sole N source other than nitrate. Ammonium is the preferred N species taken up by rice [15]. Root development is strongly affected by the plant's nutritional status and by the external availability of nutrients [16][17]. Ammonium is complementary to nitrate in shaping lateral root development and, in Arabidopsis, the stimulation of lateral root branching by ammonium occurs in an AMT1;3-dependent manner [11]. Increased expression of OsPTR9 promoted the growth of lateral roots, while a lower number of lateral roots were found in the osptr9 mutant and the OsPTR9-RNAi lines, suggesting that OsPTR9 contributes to ammonium-stimulated lateral root branching. In maize seedlings, the time required for the entire cap to be displaced by a new set of cells ranges from 24 h to 7 days, depending on growth conditions [18]. Abnormal cell displacement of the root cap in the osptr9 mutant and the OsPTR9-RNAi lines might block root growth into soil, while the thickened cell wall of the osptr9 mutant and the OsPTR9-RNAi lines may hinder lateral root formation leading to reduced root surface area for N uptake. Dense cytoplasm accumulated in the cortical fibre cells of the OsPTR9-RNAi lines and the osptr9 mutant, which might suggest a transportation obstacle due to the down-expression of OsPTR9 leading to cytoplasm accumulation in cells on the outside of the cortex. Rice roots in paddy soil prefer ammonium as the N source [15], and the major N forms in the xylem sap of rice plants are Gln and Asn [19]. Down-regulation of OsPTR9 expression caused decreased concentrations of some amino acids in roots and leaves, while many amino acids accumulated in stems. These might be caused by the abnormal development of the stem, which resulted in short and slim plants, and a reduced and disordered arrangement of the outer vascular bundle. These may, finally, block N translocation from source organs (leaves and roots) to sink (seed) resulting in nutrient accumulation in the stems and a reduced number of filled seeds. Generally, N partitioning to leaves positively regulates photosynthesis and consequently improves allocation of carbohydrates to sink tissues for vegetative and reproductive growth [20]. The changed levels and partitioning of amino acids and proteins might lead to the observed growth effects and reduced N translocation to seeds.

N recycling from leaves is important for increased grain yields in OsPTR9-over-expressing plants

The leaves are sinks for N during the vegetative stage; subsequently, this N is remobilized to the developing seeds. Up to 80% of grain N contents are derived from leaves in rice and wheat [21] [22] [23]. The high transport rate of amino acids is an essential prerequisite for seed development. Down-regulation of OsPTR9 resulted in higher concentrations of amino acids in the stems, suggesting that OsPTR9 directly or indirectly affected the transport of amino acids to seeds. Over-expression of OsPTR9 also promoted ammonium uptake, which might be the reason for the up-regulation of OsAMT1;2 expression in the OsPTR9-over-expressing lines, as OsAMT1;2 expression was shown to be induced by ammonium [12].

Mutation

Phenotypes of rice plants with altered expression of OsPTR9. (from reference [1]).

An OsPTR9 T-DNA insertion mutant (04Z11AH79, osptr9) was obtained from the Rice Mutant Database at Huazhong Agricultural University, China (http://rmd.ncpgr.cn/). One T-DNA copy was inserted in the first exon of OsPTR9, that is, 521 nucleotides downstream of the start codon of the OsPTR9 gene, as verified by sequencing the flanking region. The homozygous mutant (osptr9) was screened and used for analysis. RT-PCR analysis revealed that OsPTR9 mRNA is absent in the osptr9 at both day and night. OsPTR9-RNAi transgenic rice plants (RNAi) were generated under control of the rice Ubi-1 promoter [24]. Nine independent OsPTR9-RNAi lines were obtained, 3 of which showed very low OsPTR9 transcript levels in panicles. To address the effect of increased OsPTR9 expression, OsPTR9 over-expressing (OE) rice was constructed under the control of the 35S promoter [25]. Three of 11 independent OE lines were obtained that accumulated large amounts of OsPTR9 transcripts.

Expression

Subcellular localization of OsPTR9-eGFP fusion protein. (from reference [1]).

OsPTR9 (LOC_06g49250) is most closely related to the members of subgroup II of the PTR/NRT1 family, containing the Arabidopsis di/tripeptide transporter AtPTR2 (At2g02040) [7]. The OsPTR9 mRNA (AK064899) encodes a protein with the domain (LGTGGIKPXV) characteristic of the PTR proteins [26] [27]. Transient expression of 35S:OsPTR9-eGFP in onion epidermal cells resulted in green fluorescence at the periphery of the cells, outside of the nucleus. In addition, stable expression of 35S:OsPTR9-eGFP in plasmolysed root cells of tobacco and roots of rice showed OsPTR9-eGFP localized to the plasma membrane.

Expression analysis of OsPTR9. (from reference [1]).

In roots, GUS staining was mainly observed in young main root tips and in the cortical fibre cells of lateral roots. Furthermore, OsPTR9 expression was higher in leaves and panicles than in roots and stems.

OsPTR9 expression is regulated by light and N source. (from reference [1]).

Higher transcript levels of OsPTR9 were observed where inorganic N (NO3−, NH4+ or NH4NO3) was the sole N source, compared with organic or mixed N sources (peptone or NH4NO3 + peptone). Preliminary experiments showed that the osptr9 mutant was more seriously affected by growth on ammonium than on nitrate (data not shown), and OsPTR9 expression was induced by both low (0.5 mm) and high (5 mm) ammonium sulphate levels. The induction of OsPTR9 expression by NH4+ occurred later than that of the ammonium transporter (OsAMT1;2).

Labs working on this gene

1. Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China 2. University of Chinese Academy of Sciences, Beijing, China 3. Key Laboratory of South China Agricultural Plant Genetics and Breeding, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China 4. Institute of Plant Sciences, University of Bern, Bern, Switzerland 5. Wuhan Bioengineering Institute, Wuhan, China

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Fang, Z., Xia, K., Yang, X., Grotemeyer, M.S., Meier, S., Rentsch, D., Xu, X., Zhang, M. (2012) Altered expression of the PTR/NRT1 homologue OsPTR9 affects nitrogen utilization efficiency, growth and grain yield in rice. Plant Biotechnol. J doi: 10.1111/pbi.12031
  2. ↑ 2.0 2.1 Weichert, A., Brinkmann, C., Komarova, N.Y., Dietrich, D., Thor, K., Meier, S., Grotemeyer, M.S. and Rentsch, D. (2012) AtPTR4 and AtPTR6 are differentially expressed, tonoplast-localized members of the peptide transporter/nitrate transporter 1 (PTR/NRT1) family. Planta, 235, 311–323.
  3. ↑ Chiang, C.S., Stacey, G. and Tsay, Y.F. (2004) Mechanisms and functional properties of two peptide transporters, AtPTR2 and fPTR2. J. Biol. Chem. 279, 30150–30157.
  4. ↑ Kanno, Y., Hanada, A., Chiba, Y., Ichikawa, T., Nakazawa, M., Matsui, M., Koshiba, T., Kamiya, Y. and Seo, M. (2012) Identification of an abscisic acid transporter by functional screening using the receptor complex as a sensor. Proc. Natl Acad. Sci. USA, 109, 9653–9658.
  5. ↑ Krouk, G., Lacombe, B. and Bielach, A. (2010) Nitrate-regulated auxin transport by NRT1. 1 defines a mechanism for nutrient sensing in plants. Dev. Cell, 18, 927–937.
  6. ↑ Nour-Eldin, H.H., Andersen, T.G., Burow, M., Madsen, S.R., Jorgensen, M.E., Olsen, C.E., Dreyer, I., Hedrich, R., Geiger, D. and Halkier, B.A. (2012) NRT/PTR transporters are essential for translocation of glucosinolate defence compounds to seeds. Nature, 488, 531–534.
  7. ↑ 7.0 7.1 Tsay, Y.F., Chiu, C.C., Tsai, C.B., Ho, C.H. and Hsu, P.K. (2007) Nitrate transporters and peptide transporters. FEBS Lett. 581, 2290–2300.
  8. ↑ Delhon, P., Gojon, A., Tillard, P. and Passama, L. (1995) Diurnal regulation of NO3− uptake in soybean plants I. Changes in NO3− influx, efflux, and N utilization in the plant during the day/night cycle. J. Exp. Bot. 46, 1585–1594.
  9. ↑ Gazzarrini, S., Lejay, L., Gojon, A., Ninnemann, O., Frommer, W.B. and von Wirén, N. (1999) Three functional transporters for constitutive, diurnally regulated, and starvation-induced uptake of ammonium into Arabidopsis roots. Plant Cell, 11, 937–948.
  10. ↑ Lam, H.M., Coschigano, K., Schultz, C., Melo-Oliveira, R., Tjaden, G., Oliveira, I., Ngai, N., Hsieh, M.H. and Coruzzi, G. (1995) Use of Arabidopsis mutants and genes to study amide amino acid biosynthesis. Plant Cell, 7, 887–898.
  11. ↑ 11.0 11.1 Lima, J.E., Kojima, S., Takahashi, H. and Wirén, N.V. (2010) Ammonium triggers lateral root branching in Arabidopsis in an ammonium transporter 1;3-dependent manner. Plant Cell, 22, 3621–3633.
  12. ↑ 12.0 12.1 Sonoda, Y., Ikeda, A., Saiki, S., von Wirén, N., Yamaya, T. and Yamaguchi, J. (2003) Distinct expression and function of three ammonium transporter Genes (OsAMT1;1-1;3) in rice. Plant Cell Physiol. 44, 726–734.
  13. ↑ Gazzarrini, S., Lejay, L., Gojon, A., Ninnemann, O., Frommer, W.B. and von Wirén, N. (1999) Three functional transporters for constitutive, diurnally regulated, and starvation-induced uptake of ammonium into Arabidopsis roots. Plant Cell, 11, 937–948.
  14. ↑ Girin, T., Lejay, L., Wirth, J., Widiez, T., Palenchar, P.M., Nazoa, P., Touraine, B., Gojon, A. and Lepetit, M. (2007) Identification of a 150 bp cis-acting element of the AtNRT2.1 promoter involved in the regulation of gene expression by the N and C status of the plant. Plant Cell Env. 30, 1366–1380.
  15. ↑ 15.0 15.1 Sasakawa, H. and Yamamoto, Y. (1978) Comparison of the uptake of nitrate and ammonium by rice seedlings. Plant Physiol. 62, 665–669.
  16. ↑ Bucio, J.L., Ramirez, A.C. and Estrella, L.H. (2003) The role of nutrient availability in regulating root architecture. Curr. Opin. Plant Biol. 6, 280–287.
  17. ↑ Forde, B. and Lorenzo, H. (2001) The nutritional control of root development. Plant Soil, 232, 51–68.
  18. ↑ Barlow, P.W. (1978) Cell displacement through the columella of the root cap of Zea mays L. Ann. Bot. 42, 783–790.
  19. ↑ Williams, L. and Miller, A. (2001) Transporters responsible for the uptake and partitioning of nitrogenous solutes. Annu. Rev. Plant Physiol. Plant Mol. Biol. 52, 659–688.
  20. ↑ Zhang, L.Z., Tan, Q.M., Lee, R., Trethewy, A., Lee, Y.H. and Tegeder, M. (2010) Altered xylem-phloem transfer of amino acids affects metabolism and leads to increased seed yield and oil content in Arabidopsis. Plant Cell, 22, 3603–3620.
  21. ↑ Kichey, T., Hirel, B., Heumez, E., Dubois, F. and Le Gouis, J. (2007) In winter wheat (Triticum aestivum L.), post-anthesis nitrogen uptake and remobilisation to the grain correlates with agronomic traits and nitrogen physiological markers. Field Crop. Res. 102, 22–32.
  22. ↑ Mae, T. and Ohira, K. (1981) The remobilization of nitrogen related to leaf growth and senescence in rice plants (Oryza sativa L.). Plant Cell Physiol. 22, 1067–1074.
  23. ↑ Tabuchi, M., Abiko, T. and Yamaya, T. (2007) Assimilation of ammonium ions an reutilization of nitrogen in rice (Oryza sativa L.). J. Exp. Bot. 58, 2319–2327.
  24. ↑ Wang, Z., Chen, C.B., Xu, Y.Y., Jiang, R.X., Han, Y., Xu, Z.H. and Chong, K. (2004) A practical vector for efficient knockdown of gene expression in rice (Oryza sativa L.). Plant Mol. Biol. Rep. 22, 409–417.
  25. ↑ Zhang, W., McElroy, D. and Wu, R. (1991) Analysis of rice Act1 5[prime] region activity in transgenic rice plants. Plant Cell, 3, 1155–1165.
  26. ↑ Dietrich, D., Hammes, U., Thor, K., Suter-Grotemeyer, M., Fluckiger, R., Slusarenko, A.J., Ward, J.M. and Rentsch, D. (2004) AtPTR1, a plasma membrane peptide transporter expressed during seed germination and in vascular tissue of Arabidopsis. Plant J. 40, 488–499.
  27. ↑ Fei, Y.J., Ganapathy, V. and Leibach, F.H. (1998) Molecular and structural features of the proton-coupled oligopeptide transporter superfamily. Prog. Nucleic Acid Res. Mol. Biol. 58, 239–261.

Structured Information

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