Abstract
Rice cultivar “Weiyou916” (Oryza sativa L. ssp. Indica) were cultured with control (10 mM NO3-) and nitrate deficient solution (0 mM NO3-) for four weeks. Nitrogen (N) deficiency significantly decreased the content of N and P, dry weight (DW) of the shoots and roots, but increased the ratio of root to shoot in O. sativa. N deficiency decreased the photosynthesis rate and the maximum quantum yield of primary photochemistry (Fv/Fm), however, increased the intercellular CO2 concentration and primary fluorescence (Fo). N deficiency significantly increased the production of H2O2 and membrane lipid peroxidation revealed as increased MDA content in O. sativa leaves. N deficiency significantly increased the contents of starch, sucrose, fructose, and malate, but did not change that of glucose and total soluble protein in O. sativa leaves. The accumulated carbohydrates and H2O2 might further accelerate biosynthesis of lignin in O. sativa leaves under N limitation. A total of 1635 genes showed differential expression in response to N deficiency revealed by Illumina sequencing. Gene Ontology (GO) analysis showed that 195 DEGs were found to highly enrich in nine GO terms. Most of DEGs involved in photosynthesis, biosynthesis of ethylene and gibberellins were downregulated, whereas most of DEGs involved in cellular transport, lignin biosynthesis and flavonoid metabolism were upregulated by N deficiency in O. sativa leaves. Results of real-time quantitative PCR (RT-qPCR) further verified the RNA-Seq data. For the first time, DEGs involved oxygen-evolving complex, phosphorus response and lignin biosynthesis were identified in rice leaves. Our RNA-Seq data provided a global view of transcriptomic profile of principal processes implicated in the adaptation of N deficiency in O. sativa and shed light on the candidate direction in rice breeding for green and sustainable agriculture.
Highlights
Nitrogen (N) is one of essential macronutrients required for plant growth and development
Soluble carbohydrate measurement showed that N deficiency significantly increased the contents of starch, sucrose and fructose by 59.98%, 70.84 and 230.36% respectively, but did not change that of glucose in O. sativa leaves (Fig 3E– 3H)
N deficiency significantly decreased the content of N, dry weight (DW) of the shoots and roots, but increased the ratio of root to shoot in O. sativa
Summary
Plant culture and N treatmentUniform seeds of rice (O. sativa L. ssp. indica) cultivar “Weiyou916” were sown in plastic tray containing semidry paddy soil. Robust and uniform seedlings with three leaves and one sprout were transplanted to hydroponic barrel containing adequate Hoagland full-strength nutrient solution. The full strength nutrient solution contained the following macronutrients (in mM): KNO3, 5; Ca(NO3) ; KH2PO4, 2; MgSO4, 2; micronutrients (in μM): H3BO3, 5; MnCl2, 6; ZnSO4, 1; CuSO4, 0.5; (NH4)6Mo7O24, 0.065; and FeSO4-EDTA, 20. In N deficient nutrient solution, 5 mM KNO3 and 5 mM Ca(NO3) were replaced by 5 mM KCl and 5mM CaCl2, respectively. Seedlings with five leaves were transplanted to new culture hydroponic barrels with sufficient (control) or without nitrogen (N deficiency). The nutrient solution was refreshed every three days. Top third and forth leaves were collected at noon on a sunny day. All the samples were wrapped in aluminum foil, immersed in liquid nitrogen and stored at −80 ̊C until extraction
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