玉米植株对大田温室气体N2O 排放的影响

利用封闭式箱法对玉米田N₂O 排放通量的观测表明,大田种植玉米后,对N₂O 排放产生了很大影响,玉米-土壤系统的N₂O 排放通量大于不种玉米的土壤。此外,植物根系能明显促进土壤中N₂O 的排放,特别是在玉米生长后期尤为明显。从播种开始到年底,施尿素导致N₂O 排放为3.3kg·hm^-2, 玉米植株为0.69kg·hm^-2, 占总排放量的17.3%.     

因子分析和聚类分析在玉米品种资源分类上的应用

本研究对201份湖北省玉米品种资源的28个性状进行了因子分析,结果前7个公因子对变异的累计方差贡献率达79.4％,前7个独立的公因子真实地反了所控制的28个性状及其相互关系．以前7个公因子为综合指标进行系统聚类,201份玉米品种聚成12类,其中A,B,H,K类综合性状较好．     

Genotypic effects on the amino acid relationships in maize (Zea mays L.) pollen and style

Summary The free amino acid content of the pollen grains and the style from three single cross hybrids (Wf9 x H55, Ky49 x Ky27, K64 x K55) and two inbred lines (Oh43, H55) was determined. No tyrosine was detected in the pollen grains of any genotype. Significant differences between pollen genotypes were found for aspartic acid, threonine, serine, lysine and histidine with no effect resulting from the vigor of the pollen source. No proline was found in the style of any genotype. Significant differences between style genotypes were obtained for threonine, serine, glutamic acid, leucine, tyrosine, ethanolanine, aminobutyric acid and histidine with a relationship between vigor of the style genotype present for tyrosine, ethanolanine and aminobutyric acid. The relationship between the pollen and style level for each amino acid as influenced by genotype was analyzed. A significant negative correlation was found only for threonine. Apparently, a complementary relationship between the pollen and style exists for some amino acids. Proline and tyrosine are available only from the pollen and style respectively. Threonine levels are balanced with varying contributions from both pollen and style depending on the genotype.     

不同杂种优势群玉米籽粒脱水速率分析

研究不同杂种优势群玉米自交系籽粒脱水速率的特性,筛选脱水速率快的自交系,为选育适应机械化作业的玉米杂交种提供借鉴。本试验采用烘干测定173份玉米自交系的籽粒的脱水速率及其相关性状,利用覆盖玉米全基因组的210对SSR标记对实验材料进行全基因组扫描,通过Structure V2.3.4 软件揭示其群体结构。对不同杂种优势群平均籽粒脱水速率进行方差分析,并筛选出各个群中籽粒灌浆速率快的自交系。研究结果如下：籽粒脱水速率在不同自交系间存在显著差异,与苞叶、穗轴及籽粒的含水率等性状间存在显著相关性。试验共筛选到脱水速率大于1%的自交系20个;授粉后40天时籽粒的含水率低于21%的自交系10个。参试自交系分成P、旅大红骨、瑞德、兰卡斯特和塘四平头5个杂种优势群;授粉后40天脱水速率依次是Reid群0.92%、Lancaster群0.85%、旅大红骨群0.82%、混合群0.80%、P群0.76%、塘四平头群0.56%。     

玉米联合固氮菌Kosakonia radicincitans GXGL-4A的分离鉴定与固氮特性研究

【目的】固氮微生物是生物固氮的主体,其菌种的选育更是生物固氮研究的基础。本实验室分离鉴定出一株新的固氮菌,并对其固氮相关活性进行初步研究。【方法】固氮菌采用Ashby无氮培养基进行分离纯化。通过形态特征分析、生理生化特征分析、16S r RNA基因序列分析和基因组扫描对固氮菌进行鉴定。利用靛酚蓝-分光光度法检测固氮菌的泌铵能力。固氮酶活性的测定使用乙炔还原法。【结果】从玉米根部分离到一株固氮菌株GXGL-4A,菌体短杆状,大小约为1.5μm×0.5μm,单个或常见2个菌体细胞串联在一起,革兰氏染色结果为阴性。16S r RNA基因序列分析结果表明该菌株与Kosakonia oryzae Fo8A1d 16S r RNA基因序列有95%的相似性,结合形态特征、生理生化特征和基因组扫描,将其命名为K.radicincitans GXGL-4A。对其进行固氮基因nif H的检测,经PCR扩增得到预期的296 bp条带;采用靛酚蓝-分光光度法,测得发酵液中铵态氮含量为2.5 mg/L,表明该菌株具有较好的泌铵能力。乙炔还原法测其固氮酶活性,以乙烯生产量表示,结果显示GXGL-4A菌株在无氮培养基上能够有效地还原乙炔,达到232.94 nmol C2H4/(m L·h)。【结论】菌株GXGL-4A是一株可较好地分泌铵的新的固氮菌,具有很好的研究价值。     

Proteomic changes in maize roots after short-term adjustment to saline growth conditions

It is of fundamental importance to understand adaptation processes leading to salt resistance. The initial effects on maize roots in the first hour after the adjustment to saline conditions were monitored to elucidate initial responses. The subsequent proteome change was monitored using a 2‐D proteomic approach. We found several new salt‐inducible proteins, whose expression has not been previously reported to be modulated by salt. A set of phosphoproteins in maize was detected but only ten proteins were phosphorylated and six proteins were dephosphorylated after the application of 25 mM NaCl for 1 h. Some of the phosphorylated maize proteins such as fructokinase, UDP‐glucosyl transferase BX9, and 2‐Cys‐peroxyredoxine were enhanced, whereas an isocitrate‐dehydrogenase, calmodulin, maturase, and a 40‐S‐ribosomal protein were dephosphorylated after adjustment to saline conditions. The initial reaction of the proteome and phosphoproteome of maize after adjustment to saline conditions reveals members of sugar signalling and cell signalling pathways such as calmodulin, and gave hint to a transduction chain which is involved in NaCl‐induced signalling. An alteration of 14‐3‐3 proteins as detected may change plasma membrane ATPase activity and cell wall growth regulators such as xyloglucane endotransglycosylase were also found to be changed immediately after the adjustment to salt stress.     

Dual targeting of organellar seryl-tRNA synthetase to maize mitochondria and chloroplasts

Aminoacyl-tRNA synthetases (AARSs) play a critical role in translation and are thus required in three plant protein-synthesizing compartments: cytosol, mitochondria and plastids. A systematic study had previously shown extensive sharing of organellar AARSs from Arabidopsis thaliana, mostly between mitochondria and chloroplasts. However, distribution of AARSs from monocot species, such as maize, has never been experimentally investigated. Here we demonstrate dual targeting of maize seryl-tRNA synthetase, SerZMo, into both mitochondria and chloroplasts using combination of complementary methods, including in vitro import assay, transient expression analysis of green fluorescent protein (GFP) fusions and immunodetection. We also show that SerZMo dual localization is established by the virtue of an ambiguous targeting peptide. Full-length SerZMo protein fused to GFP is targeted to chloroplast stromules, indicating that SerZMo protein performs its function in plastid stroma. The deletion mutant lacking N-terminal region of the ambiguous SerZMo targeting peptide was neither targeted into mitochondria nor chloroplasts, indicating the importance of this region in both mitochondrial and chloroplastic import.     

Calreticulin mRNA and protein are localized to protein bodies in storage maize callus cells

Maize callus cells possess numerous protein bodies which develop as sub-compartments of the endoplasmic reticulum. We localized maize calreticulin mRNAs and protein in maize callus cells using in situ hybridization and immunocytochemistry. Calreticulin mRNAs were selectively targeted to the endoplasmic reticulum (ER) subdomains surrounding protein bodies. Profilin mRNAs, used as a positive control for in situ hybridization experiments, showed distinct and rather diffuse localization pattern. Using both, immunofluorescence and immunogold electron microscopy localization techniques, calreticulin was found to be enriched around and within protein bodies in maize callus storage cells. As a positive control for reticuloplasmins, HDEL antibody revealed labelling of protein bodies and of the nuclear envelope. The identity of protein bodies was confirmed by specific binding of an α zein antibody. These data suggest that calreticulin mRNA is targeted towards protein body forming subdomains of the ER, and that calreticulin is localized and enriched in these protein bodies. The possibility that calreticulin plays an important role in zein retention within the ER and/or its assembly and packaging into protein bodies during protein body biogenesis in maize callus is discussed.     

Occurrence of aflatoxin in three maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) hybrids over 5 years in Northern Mississippi

Aflatoxins are produced as secondary metabolites under conducive climatic conditions by Aspergillus flavus. The incidence of aflatoxin varies with environmental conditions, genotype, and location. An expanded understanding of the interaction of the plant, fungus, and weather conditions is needed to further elucidate the field infection process of maize by A. flavus and subsequent aflatoxin contamination. One of the problems in evaluating maize hybrids for resistance to kernel infection and aflatoxin contamination is identifying a time period and environmental conditions that are most advantageous. Three maize genotypes (Pioneer Brand 3223, Mo18W × Mp313E, and Mp313E × Mp420) were evaluated from 1998 to 2002 in response to A. flavus inoculation and aflatoxin contamination and weather conditions favorable for aflatoxin contamination were identified. The highest aflatoxin levels were observed in 1998 and 2000 (1186 and 901 ng g⁻¹; P < 0.0001); while the lowest levels were detected in 1999 (39 ng g⁻¹). Pioneer 3223 had significantly higher levels (1198 ng g⁻¹) than Mp313E × Mp420 (205 ng g⁻¹), and Mo18W ×Mp313E (161 ng g⁻¹; P < 0.0001). The hybrids had six weather-related variables in common that were positively correlated with aflatoxin accumulation. Four of these occurred during 65–85 days after planting and were temperature-related. These results suggest that regardless of the hybrid’s maturity or physiological development, the time from 65 to 85 days after planting may be indicative of a period of stress which leads to greater aflatoxin accumulation at harvest. The U.S. Government's right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.