Changes in Thermostability of Photosystem Ⅱ and Leaf Lipid Composition of Rice Mutant with Deficiency of Light-harvesting Chlorophyll Protein Complexes

We studied the difference in thermostability of photosystem Ⅱ (PSⅡ) and leaf lipid composition between a T-DNA insertion mutant rice (Oryza sativa L.) VG28 and its wild type Zhonghua11. Native green gel and SDS-PAGE electrophoreses revealed that the mutant VG28 lacked all light-harvesting chlorophyll a/b protein complexes. Both the mutant and wild type were sensitive to high temperatures, and the maximal efficiency of PSⅡ photochemistry (Fv/Fm) and oxygen-evolving activity of PSⅡ in leaves significantly decreased with increasing temperature. However, the PSⅡ activity of the mutant was markedly more sensitive to high temperatures than that of the wild type. Lipid composition analysis showed that the mutant had less phosphatidylglycerol and sulfoquinovosyl diacylglycerol compared with the wild type. Fatty acid analysis revealed that the mutant had an obvious decrease in the content of unsaturation of membrane lipids on the thermostability of PSll are discussed.     

根际微生物促进水稻氮利用的机制

根际微生物影响植物的生长及环境适应性。不同种属、不同种群的植物影响其环境微生物群落; 反之, 根际微生物也影响宿主植物生长发育与生态适应性。植物与根际微生物的互作现象及其机制, 是生命科学研究关注的热点, 也是农业微生物利用的关键问题。近期, 中国科学家在该领域取得了突破性进展。通过对不同籼稻(Oryza sativa subsp. indica)和粳稻(O. sativa subsp. japonica)品种的根际微生物组进行研究, 发现籼稻根际比粳稻根际富集更多参与氮代谢的微生物群落, 且该现象与硝酸盐转运蛋白基因NRT1.1B在籼粳之间的自然变异相关联。通过对籼稻接种籼稻根际特异富集的微生物群体可以提高前者对有机氮的利用, 促进其生长。该研究揭示了籼稻和粳稻根际微生物分化的分子基础, 展示了利用根际微生物提高水稻营养高效吸收的应用前景。     

TMSEG: Novel prediction of transmembrane helices

Transmembrane proteins (TMPs) are important drug targets because they are essential for signaling, regulation, and transport. Despite important breakthroughs, experimental structure determination remains challenging for TMPs. Various methods have bridged the gap by predicting transmembrane helices (TMHs), but room for improvement remains. Here, we present TMSEG, a novel method identifying TMPs and accurately predicting their TMHs and their topology. The method combines machine learning with empirical filters. Testing it on a non‐redundant dataset of 41 TMPs and 285 soluble proteins, and applying strict performance measures, TMSEG outperformed the state‐of‐the‐art in our hands. TMSEG correctly distinguished helical TMPs from other proteins with a sensitivity of 98 ± 2% and a false positive rate as low as 3 ± 1%. Individual TMHs were predicted with a precision of 87 ± 3% and recall of 84 ± 3%. Furthermore, in 63 ± 6% of helical TMPs the placement of all TMHs and their inside/outside topology was correctly predicted. There are two main features that distinguish TMSEG from other methods. First, the errors in finding all helical TMPs in an organism are significantly reduced. For example, in human this leads to 200 and 1600 fewer misclassifications compared to the second and third best method available, and 4400 fewer mistakes than by a simple hydrophobicity‐based method. Second, TMSEG provides an add‐on improvement for any existing method to benefit from. Proteins 2016; 84:1706–1716. © 2016 Wiley Periodicals, Inc.     

根际微生物促进水稻氮利用的机制

根际微生物影响植物的生长及环境适应性。不同种属、不同种群的植物影响其环境微生物群落;反之,根际微生物也影响宿主植物生长发育与生态适应性。植物与根际微生物的互作现象及其机制,是生命科学研究关注的热点,也是农业微生物利用的关键问题。近期,中国科学家在该领域取得了突破性进展。通过对不同籼稻(Oryza sativa subsp. indica)和粳稻(O. sativa subsp. japonica)品种的根际微生物组进行研究,发现籼稻根际比粳稻根际富集更多参与氮代谢的微生物群落,且该现象与硝酸盐转运蛋白基因NRT1.1B在籼粳之间的自然变异相关联。通过对籼稻接种籼稻根际特异富集的微生物群体可以提高前者对有机氮的利用,促进其生长。该研究揭示了籼稻和粳稻根际微生物分化的分子基础,展示了利用根际微生物提高水稻营养高效吸收的应用前景。     

Changes in Thermostability of Photosystem Ⅱ and Leaf Lipid Composition of Rice Mutant with Deficiency of Light-harvesting Chlorophyll a/b Protein Complexes

We studied the difference in thermostability of photosystem Ⅱ （PSII） and leaf lipid composition between a T-DNA insertion mutant rice （Oryza sativa L.） VG28 and its wild type Zhonghuau. Native green gel and SDS-PAGE electrophoreses revealed that the mutant VG28 lacked all light-harvesting chlorophyll a/b protein complexes. Both the mutant and wild type were sensitive to high temperatures, and the maximal efficiency of PSII photochemistry （FJ Fm） and oxygen-evolving activity of PSII in leaves significantly decreased with increasing temperature. However, the PSII activity of the mutant was markedly more sensitive to high temperatures than that of the wild type. Lipid composition analysis showed that the mutant had less phosphatidylglycerol and sulfoquinovosyl diacylglycerol compared with the wild type. Fatty acid analysis revealed that the mutant had an obvious decrease in the content of 16：1t and a marked increase in the content of 18：3 compared with the wild type. The effects of lipid composition and unsaturation of membrane lipids on the thermostability of PSII are discussed.     

Isolation and expression analysis of two rice genes encoding the major intrinsic protein

We isolated two rice cDNAs (rMip1 and rTip1) which are homologous to the genes encoding the major intrinsic protein (Mip) (soybean nod-26 and Arabidopsis -Tip), respectively. Expression of rTip1 in shoots and roots of rice seedlings was enhanced by water stress, salt stress and exogenous ABA. rMip1 was expressed only in shoots. Although mRNA level of rMip1 in shoots was induced to a small extent by exogenous ABA, it did not show any increase under water or salt stress over the course of 12 h. On the basis of the differential expression patterns and evolutional distinctions, it is suggested that the possible channel proteins encoded by rMip1 and rTip1 genes may function in different transport systems.     

A Comparative Study on PSⅡ Light Harvesting Chlorophyll a/b Protein Complexes Between Spinach and Cucumber

PS Ⅱ light harvesting chlorophyll a/b protein complexes (LHC Ⅱ ) were isolated from chloroplast of spinach (Spinacia oleracea Mill. ) and cucumber (Cucumis sativus L. ). Comparative studies were made on the polymerized forms. Chl a/b ratio, spectral characteristics and polypeptide components of these two kinds of LHC Ⅱ. Experimental results showed that the LHC Ⅱ from spinach had a Chl a/b ratio of 1.33 and the LHC Ⅱ from cucumber had a Chl a/b ratio of 1.77. The spectral characteristics of the LHC Ⅱ from cucumber also indicated the enrichment of Chl b in this LHC Ⅱ . There was also obvious differences in the polypeptide components between these two kinds of LHC Ⅱ, the LHC Ⅱ of spinach contained a 27 kD and a 25 kD polypeptides, while the LHC Ⅱ of cucumber contained only a 27 kD polypeptide. This showed that the 25 kD polypeptide contained less Chl b. The analysis of the chlorophyll protein complexes showed that the monomer, dimer and trimer of the LHC Ⅱ of spinach were composed of two polypeptides, while all the polymerized forms of cucumber’s LHC Ⅱ were composed of one polypeptide.     

Oxalate Accumulation as Regulated by Nitrogen Forms and Its Relationship to Photosynthesis in Rice （Oryza sativa L.）

Four-leaf rice seedlings (Oryza sativa L.), which had been cultivated in Kimura B complete nutrient solution, were treated with two nitrogen forms by replacing the nitrogen element in the complete solution with sole nitrate or ammonium (2.86 mmol/L). Nitrate-N nutrition tended to increase oxalate content in all parts of the plant, including the leaves, stems, roots, and root exudates, whereas ammonium had the opposite effect. Consequently, marked differences in oxalate content were observed between the two treatments throughout the time tested (0-12 d), with maximal differences of approximately 12-fold at 6d after treatment. Photosynthetic/respiratory parameters were examined over time simultaneously with changes in oxalate content. Net photosynthetic rate, chlorophyll fluorescence parameters (i.e. maximal photochemical efficiency (Fv/Fm) and photochemical quantum yields of photosystem (PS)II (ΦPSⅡ)), and respiratory rate were not significantly different between plants treated with the two nitrogen forms, although ammonium-fed plants had apparently higher leaf chlorophyll content than nitrate-fed plants. Leaf glucose content was altered little, but the content of fructose, sucrose, and total soluble sugar was significantly higher in the leaves of ammonium-fed plants than nitrate-fed plants. The results indicate that nitrate/ammonium may serve as efficient regulators of oxalate accumulation owing to regulation of metabolism in rice leaves rather than oxalate downward transfer and root excretion, and that photosynthetic metabolism is not directly correlated with the regulation of oxalate accumulation in rice plants.     

田间非饱和流条件下土壤硝态氮运移的模拟

运用马尔可夫过程的理论 ,建立了土壤非饱和流条件下 ,模拟硝态氮通过土层运移的随机模型 .模型把时间可变系统假设为由紧密相连的时间均质情况相接而成 ,使得运用马尔可夫过程成为可能 ,在给定土壤水流量及汇源项转移强度的土壤层次中 ,给出了硝态氮溶质的统计分布 .模型将随机过程与确定性过程相结合 ,在计算各土层间的转移概率时考虑了硝态氮的作物吸收、淋洗、硝化和反硝化等主要过程 ,并用相关函数修正 N素转化关系 .在褐土农田土壤非饱和流条件下 ,用微区试验对该模型运行效果进行了验证 ,结果显示模拟计算值与实测值之间吻合性较好 ,说明模型可以用于相似类型区 ,预测和评价土壤 -作物系统中硝态氮溶质的运移行为 .