Li Haixing, Liang Zhijun, Ding Guangda, Shi Lei, Xu Fangsen, Cai Hongmei
Plant Nutrigenic and Molecular Biology, College of Resources and Environment, Huazhong Agricultural University Wuhan, China.
Front Plant Sci. 2016 Aug 30;7:1318. doi: 10.3389/fpls.2016.01318. eCollection 2016.
Light and temperature are two particularly important environmental cues for plant survival. Carbon and nitrogen are two essential macronutrients required for plant growth and development, and cellular carbon and nitrogen metabolism must be tightly coordinated. In order to understand how the natural light/dark cycle regulates carbon and nitrogen metabolism in rice plants, we analyzed the photosynthesis, key carbon-nitrogen metabolites, and enzyme activities, and differentially expressed genes and miRNAs involved in the carbon and nitrogen metabolic pathway in rice shoots at the following times: 2:00, 6:00, 10:00, 14:00, 18:00, and 22:00. Our results indicated that more CO2 was fixed into carbohydrates by a high net photosynthetic rate, respiratory rate, and stomatal conductance in the daytime. Although high levels of the nitrate reductase activity, free ammonium and carbohydrates were exhibited in the daytime, the protein synthesis was not significantly facilitated by the light and temperature. In mRNA sequencing, the carbon and nitrogen metabolism-related differentially expressed genes were obtained, which could be divided into eight groups: photosynthesis, TCA cycle, sugar transport, sugar metabolism, nitrogen transport, nitrogen reduction, amino acid metabolism, and nitrogen regulation. Additionally, a total of 78,306 alternative splicing events have been identified, which primarily belong to alternative 5' donor sites, alternative 3' acceptor sites, intron retention, and exon skipping. In sRNA sequencing, four carbon and nitrogen metabolism-related miRNAs (osa-miR1440b, osa-miR2876-5p, osa-miR1877 and osa-miR5799) were determined to be regulated by natural light/dark cycle. The expression level analysis showed that the four carbon and nitrogen metabolism-related miRNAs negatively regulated their target genes. These results may provide a good strategy to study how natural light/dark cycle regulates carbon and nitrogen metabolism to ensure plant growth and development.
光和温度是植物生存的两个特别重要的环境信号。碳和氮是植物生长发育所需的两种必需大量营养素，细胞碳和氮代谢必须紧密协调。为了了解自然光/暗循环如何调节水稻植株的碳和氮代谢，我们分析了以下时间点水稻地上部的光合作用、关键碳氮代谢物、酶活性以及参与碳氮代谢途径的差异表达基因和微小RNA（miRNA）：2:00、6:00、10:00、14:00、18:00和22:00。我们的结果表明，白天较高的净光合速率、呼吸速率和气孔导度使更多的二氧化碳固定为碳水化合物。虽然白天硝酸盐还原酶活性、游离铵和碳水化合物水平较高，但光和温度并未显著促进蛋白质合成。在mRNA测序中，获得了与碳氮代谢相关的差异表达基因，可分为八组：光合作用、三羧酸循环、糖转运、糖代谢、氮转运、氮还原、氨基酸代谢和氮调节。此外，共鉴定出78306个可变剪接事件，主要属于可变5'供体位点、可变3'受体位点、内含子保留和外显子跳跃。在小RNA测序中，确定了四个与碳氮代谢相关的miRNA（osa-miR1440b、osa-miR2876-5p、osa-miR1877和osa-miR5799）受自然光/暗循环调控。表达水平分析表明，这四个与碳氮代谢相关的miRNA对其靶基因起负调控作用。这些结果可能为研究自然光/暗循环如何调节碳氮代谢以确保植物生长发育提供一个良好的策略。
