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Additional nitrogen fertilization at heading time of rice down-regulates cellulose synthesis in seed endosperm.

Midorikawa K, Kuroda M, Terauchi K, Hoshi M, Ikenaga S, Ishimaru Y, Abe K, Asakura T - PLoS ONE (2014)

Bottom Line: As a result, it was assessed that genes associated with molecular processes such as photosynthesis, trehalose metabolism, carbon fixation, amino acid metabolism, and cell wall metabolism were differentially expressed.Moreover, additional nitrogen fertilization caused accumulation of storage proteins and up-regulated Cys-poor prolamin mRNA expression.These data suggest that additional nitrogen fertilization at heading time changes the expression of some storage substance-related genes and reduces cellulose levels in endosperm.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.

ABSTRACT
The balance between carbon and nitrogen is a key determinant of seed storage components, and thus, is of great importance to rice and other seed-based food crops. To clarify the influence of the rhizosphere carbon/nitrogen balance during the maturation stage of several seed components, transcriptome analysis was performed on the seeds from rice plants that were provided additional nitrogen fertilization at heading time. As a result, it was assessed that genes associated with molecular processes such as photosynthesis, trehalose metabolism, carbon fixation, amino acid metabolism, and cell wall metabolism were differentially expressed. Moreover, cellulose and sucrose synthases, which are involved in cellulose synthesis, were down-regulated. Therefore, we compared cellulose content of mature seeds that were treated with additional nitrogen fertilization with those from control plants using calcofluor staining. In these experiments, cellulose content in endosperm from plants receiving additional nitrogen fertilization was less than that in control endosperm. Other starch synthesis-related genes such as starch synthase 1, starch phosphorylase 2, and branching enzyme 3 were also down-regulated, whereas some α-amylase and β-amylase genes were up-regulated. On the other hand, mRNA expression of amino acid biosynthesis-related molecules was up-regulated. Moreover, additional nitrogen fertilization caused accumulation of storage proteins and up-regulated Cys-poor prolamin mRNA expression. These data suggest that additional nitrogen fertilization at heading time changes the expression of some storage substance-related genes and reduces cellulose levels in endosperm.

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Analysis of proteins in polished rice from incubator cultivated plants.Three independent plants were selected from the N-fertilized and control plots. (A) Nitrogen content of polished rice was determined using a Rapid-N analyzer. Error bars represent standard deviation (SD; *P<0.001) (B) Protein composition of polished rice was analyzed using SDS-PAGE. Soluble proteins and insoluble proteins were extracted sequentially from the same sample. Major storage proteins in rice seed were extracted as insoluble proteins, as indicated at the right side of the gel.
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pone-0098738-g003: Analysis of proteins in polished rice from incubator cultivated plants.Three independent plants were selected from the N-fertilized and control plots. (A) Nitrogen content of polished rice was determined using a Rapid-N analyzer. Error bars represent standard deviation (SD; *P<0.001) (B) Protein composition of polished rice was analyzed using SDS-PAGE. Soluble proteins and insoluble proteins were extracted sequentially from the same sample. Major storage proteins in rice seed were extracted as insoluble proteins, as indicated at the right side of the gel.

Mentions: To investigate the genomic response to nitrogen fertilization, a plant incubator was used to control growth conditions between replicate experiments. Rice plants from the two experimental plots were morphologically similar at heading stage, although the leaf blades of N-fertilized rice clearly showed a darker green color than those of the control group (Fig. S1). Mature seeds were obtained from all but one control plant. Moreover, the average maturation rate was calculated from the number of mature seeds divided by the number of spikelets, and was found to be 88.0% in the N-fertilization plot and 92.2% in the control plot. Nitrogen content of mature polished grains was much higher in plants from the N-fertilized plot (Fig. 3A), and this difference of seed nitrogen content between two plots was greater in incubator cultivation than in field trial. In incubator cultivation, water was pooled in trays and plant sizes were reduced by removing tillers. Thus, all fertilizer remained in incubator trays, allowing for higher quantities of nitrogen to be utilized for grain development. Accordingly, higher nitrogen content of seeds from the N-fertilized plot was reflected by band density of insoluble proteins in SDS-PAGE analysis (Fig. 3B). Each density corresponding to glutelin and a 13 kDa prolamin was higher in the case of N-fertilized plot.


Additional nitrogen fertilization at heading time of rice down-regulates cellulose synthesis in seed endosperm.

Midorikawa K, Kuroda M, Terauchi K, Hoshi M, Ikenaga S, Ishimaru Y, Abe K, Asakura T - PLoS ONE (2014)

Analysis of proteins in polished rice from incubator cultivated plants.Three independent plants were selected from the N-fertilized and control plots. (A) Nitrogen content of polished rice was determined using a Rapid-N analyzer. Error bars represent standard deviation (SD; *P<0.001) (B) Protein composition of polished rice was analyzed using SDS-PAGE. Soluble proteins and insoluble proteins were extracted sequentially from the same sample. Major storage proteins in rice seed were extracted as insoluble proteins, as indicated at the right side of the gel.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4048278&req=5

pone-0098738-g003: Analysis of proteins in polished rice from incubator cultivated plants.Three independent plants were selected from the N-fertilized and control plots. (A) Nitrogen content of polished rice was determined using a Rapid-N analyzer. Error bars represent standard deviation (SD; *P<0.001) (B) Protein composition of polished rice was analyzed using SDS-PAGE. Soluble proteins and insoluble proteins were extracted sequentially from the same sample. Major storage proteins in rice seed were extracted as insoluble proteins, as indicated at the right side of the gel.
Mentions: To investigate the genomic response to nitrogen fertilization, a plant incubator was used to control growth conditions between replicate experiments. Rice plants from the two experimental plots were morphologically similar at heading stage, although the leaf blades of N-fertilized rice clearly showed a darker green color than those of the control group (Fig. S1). Mature seeds were obtained from all but one control plant. Moreover, the average maturation rate was calculated from the number of mature seeds divided by the number of spikelets, and was found to be 88.0% in the N-fertilization plot and 92.2% in the control plot. Nitrogen content of mature polished grains was much higher in plants from the N-fertilized plot (Fig. 3A), and this difference of seed nitrogen content between two plots was greater in incubator cultivation than in field trial. In incubator cultivation, water was pooled in trays and plant sizes were reduced by removing tillers. Thus, all fertilizer remained in incubator trays, allowing for higher quantities of nitrogen to be utilized for grain development. Accordingly, higher nitrogen content of seeds from the N-fertilized plot was reflected by band density of insoluble proteins in SDS-PAGE analysis (Fig. 3B). Each density corresponding to glutelin and a 13 kDa prolamin was higher in the case of N-fertilized plot.

Bottom Line: As a result, it was assessed that genes associated with molecular processes such as photosynthesis, trehalose metabolism, carbon fixation, amino acid metabolism, and cell wall metabolism were differentially expressed.Moreover, additional nitrogen fertilization caused accumulation of storage proteins and up-regulated Cys-poor prolamin mRNA expression.These data suggest that additional nitrogen fertilization at heading time changes the expression of some storage substance-related genes and reduces cellulose levels in endosperm.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.

ABSTRACT
The balance between carbon and nitrogen is a key determinant of seed storage components, and thus, is of great importance to rice and other seed-based food crops. To clarify the influence of the rhizosphere carbon/nitrogen balance during the maturation stage of several seed components, transcriptome analysis was performed on the seeds from rice plants that were provided additional nitrogen fertilization at heading time. As a result, it was assessed that genes associated with molecular processes such as photosynthesis, trehalose metabolism, carbon fixation, amino acid metabolism, and cell wall metabolism were differentially expressed. Moreover, cellulose and sucrose synthases, which are involved in cellulose synthesis, were down-regulated. Therefore, we compared cellulose content of mature seeds that were treated with additional nitrogen fertilization with those from control plants using calcofluor staining. In these experiments, cellulose content in endosperm from plants receiving additional nitrogen fertilization was less than that in control endosperm. Other starch synthesis-related genes such as starch synthase 1, starch phosphorylase 2, and branching enzyme 3 were also down-regulated, whereas some α-amylase and β-amylase genes were up-regulated. On the other hand, mRNA expression of amino acid biosynthesis-related molecules was up-regulated. Moreover, additional nitrogen fertilization caused accumulation of storage proteins and up-regulated Cys-poor prolamin mRNA expression. These data suggest that additional nitrogen fertilization at heading time changes the expression of some storage substance-related genes and reduces cellulose levels in endosperm.

Show MeSH