| Agricultural sciences |
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| Changes of nitrogen metabolism enzyme activities and protein content in response to low light during the seed filling stage in rice |
| XU Guangli, LIU Jia, LIANG Chenggang, WANG Yan, DING Chunbang, LI Tian |
| (1. College of Agronomy, Sichuan Agricultural University/Key Laboratory of Crop Physiology, Ecology and Cultivation in Southwest, Ministry of Agriculture, Chengdu 611130, China; 2. College of Life Science, Sichuan Agricultural University, Ya’an 625014, Sichuan, China) |
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Abstract Light condition is one of the important factors affecting plant growth. During plant growth, light deficiency will result in the decrease in carbon fixation, photosynthetic efficiency, and leaf senescence acceleration, and thus decrease yield evidently. Besides yield, light also affect the rice qualities through influencing the seed compositions such as protein. Many studies have been carried out to evaluate the effect of light on protein synthesis. For example, previous studies have been certified that the protein accumulation is increased during the seed filling stage, as well as amino acids. The enzymes of glutamine synthetase (GS), glutamic oxalo-acetic transaminase (GOT), and glutamate pyruvate transaminase (GPT) are considered as the key enzymes regulating the synthesis of protein. Almost 95% of N was absorbed through GS/glutamate synthetase (GOGAT) cycle in plants and converted into glutamic acid (Glu) and glutamine (Gln). The Glu and Gln are then converted into other amino acids which provide the precursor materials for protein synthesis through the transamination reactions of GOT and GPT. However, researches about the effect of the activities of GS, GOT and GPT on amino acid and protein synthesis of rice are limited, especially under stress conditions such as low light. Based on previous studies, we carried out this experiment to evaluate the effect of low light on key enzyme activities of nitrogen metabolism and protein accumulation during the seed filling stage. The aims of this study were to study the dynamic changes of GS, GOT and GPT under different low light conditions during the seed filling stage, and evaluate the relationships between the activities of enzymes and protein accumulation. The experiment was initiated at Sichuan Agricultural University, Ya’an, China, in 2013. Four cultivars including japonica cultivars Akitakomachi and Koshihikari, indica cultivar IR72, and hybrid indica cultivar Gangyou 527 were selected as the materials. All the cultivars were managed routinely till the flowering stage, then 25% shading (A1) and 50% shading (A2), were set respectively as the treatments till maturity by using shade net, and natural condition was set as CK. Each treatment plot was repeated 3 times and the rice panicles which grown uniformly were marked for further sample collection. After 10 days of treatments, the seed samples were collected per 7-day period till maturity and stored in freezer at -80 ℃. After harvest, the samples were used to measure GS, GOT and GPT activities, as well as soluble protein, total protein and amino acid contents. Results showed that the GS activities were significantly decreased by 2001%-3052% at A2 than A1 (1161%-1936%) compared with CK, whereas, the activities of GOT and GPT increased significantly at A2 (GOT increased by 2607%-3682% and GPT increased by 2607%-6107%) than A1(GOT increased by 1402%-2302% GPT increased by 1181%-3383%) compared with CK In consistent with GOT and GPT, patterns of soluble protein, total protein, as well as amino acids were also significantly increased under low light conditions especially at A2 (compared with CK, soluble protein increased by 3119%-7051%, total protein increased by 1602%-2889%, and amino acids increased by 1604%-2248% at A2). The correlation analysis showed that GS activity was negatively correlated to soluble protein, total protein and amino acids under low light conditions, however, GOT and GPT showed positive correlations with soluble protein, total protein and amino acids. Based on the results, we speculated that the synthesis of protein of rice grain was more significantly affected by GOT and GPT which tended to increase the accumulation of both protein and amino acids, compared with GS. In addition, in consistent with previous studies, the low light conditions were beneficial for protein and amino acid synthesis of rice grain during the seed filling stage.
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Published: 20 January 2016
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灌浆结实期弱光对水稻籽粒氮代谢酶及蛋白质含量的影响
为了探讨水稻灌浆结实期弱光胁迫对籽粒氮代谢关键酶及蛋白质的影响,以粳稻越光和秋田小町,籼稻IR72,以及杂交籼稻冈优527等4个品种为材料,在灌浆结实期分别进行遮光25%（A1）和遮光50%（A2）为处理,以自然条件为对照（CK）,研究了不同程度弱光对氮代谢关键酶谷氨酰胺合成酶（glutamine synthetase,GS）、谷氨酸-草酰乙酸转氨酶（glutamic oxalo-acetic transaminase,GOT）和谷氨酸-丙酮酸转氨酶（glutamate pyruvate transaminase,GPT）活性和可溶性蛋白质、蛋白质以及氨基酸含量的影响。结果表明,弱光下GS活性显著降低,且随着弱光程度加深而下降加重,而GOT、GPT、可溶性蛋白质、蛋白质和氨基酸含量在弱光下均显著提高,且提高幅度A2>A1。GS活性与可溶性蛋白质、蛋白质以及氨基酸含量均呈显著负相关,而GOT和GPT与可溶性蛋白质、蛋白质和氨基酸均呈极显著正相关。由此推测相对于GS,灌浆结实期水稻籽粒中GOT和GPT活性对蛋白质的合成影响更加显著。
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