两种镉积累型小麦根际微生物群落结构及功能多样性

为探究不同积累型小麦品种对根际微生物群落结构及功能多样性的影响,以镉低积累型小麦济麦22和镉高积累型小麦冀5265为研究材料,采用分离培养法和Biolog-Eco微平板法分析根际细菌数量、可培养优势群落结构以及微生物群落功能多样性。结果表明：污染土壤济麦22根际总细菌数量和抗Cd细菌数量均显著高于冀5265,而非污染土壤中两品种间无差异。污染土济麦22根际发现较多产脲酶和高镉抗性菌株(200 mg/L)。污染土济麦22根际优势菌多为Arthrobacter sp.和Bacillus sp.,冀5265根际优势菌主要为Streptomyces sp.;非污染土济麦22与冀5265根际优势菌群相似,均以Bacillus sp.为主。Biolog试验结果表明,两个小麦品种根际微生物群落对碳源的利用能力存在差异,济麦22根际微生物AWCD值、Mc Intosh指数、Shannon-Wiener指数、Simpson指数在污染土和无污染土中均显著高于冀5265。因此,污染土壤中不同积累型小麦品种根际微生物群落结构及功能多样性均存在差异,该研究结果对于揭示高低积累型小麦根际微生物机制提供了重要参考依...     

小麦矮秆突变体jm22d响应赤霉素处理的转录组学分析

为拓宽小麦矮秆遗传资源,利用γ射线辐照济麦22获得了一个赤霉素不敏感型矮秆突变体jm22d。株高相关性状调查结果及茎秆细胞学试验显示,jm22d株高为53±1.8 cm,比野生型（WT）低约20 cm。jm22d整株茎秆共有4节,比WT少一节且各节间长度显著小于WT。与WT相比,jm22d茎秆细胞长度缩短。赤霉素含量测定发现,jm22d叶片中赤霉素含量高于WT,而茎秆中赤霉素含量低于WT（P<0.01）,因此,jm22d株高降低与赤霉素转运途径出现异常有关。为了深入研究jm22d对赤霉素的响应机理,对jm22d和WT幼苗进行赤霉素处理,分别收取处理0（D0）、1（D1）和3 d（D3）的样品进行转录组学分析。结果表明,与WT相比,在jm22d中共筛选到696个上调和1 067个下调的表达基因,其中62个和349个基因在3个时间点分别表现为上调和下调表达。叶绿素含量测定表明,jm22d中叶绿素含量随赤霉素处理时间的延长而降低,聚类分析结果表明,差异表达基因主要富集在光合作用-天线蛋白（photosynthesis-antenna proteins,ko00196）、卟啉和叶绿素代谢（porphyrin and chlorophyll metabolism,ko00860）、亚油酸新陈代谢（linoleic acid metabolism,ko00591）等通路,因此赤霉素处理对jm22d体内叶绿素含量的积累具有抑制作用。通过KEGG分析在植物激素信号转导途径中挖掘到5个差异表达基因（TraesCS2B01G582300、TraesCS2B01G600800、TraesCS2B01G556600、TraesCS2B01G630000和TraesCS6B01G439600）参与生长素、细胞分裂素等激素代谢途径,这些基因在jm22d中显著下调,这可能是jm22d矮化的重要原因。研究结果为矮秆突变体矮化机制的解析提供了重要参考。     

Functional mitochondrial complex I is required by tobacco leaves for optimal photosynthetic performance in photorespiratory conditions and during transients

The importance of the mitochondrial electron transport chain in photosynthesis was studied using the tobacco (Nicotiana sylvestris) mutant CMSII, which lacks functional complex I. Rubisco activities and oxygen evolution at saturating CO(2) showed that photosynthetic capacity in the mutant was at least as high as in wild-type (WT) leaves. Despite this, steady-state photosynthesis in the mutant was reduced by 20% to 30% at atmospheric CO(2) levels. The inhibition of photosynthesis was alleviated by high CO(2) or low O(2). The mutant showed a prolonged induction of photosynthesis, which was exacerbated in conditions favoring photorespiration and which was accompanied by increased extractable NADP-malate dehydrogenase activity. Feeding experiments with leaf discs demonstrated that CMSII had a lower capacity than the WT for glycine (Gly) oxidation in the dark. Analysis of the postillumination burst in CO(2) evolution showed that this was not because of insufficient Gly decarboxylase capacity. Despite the lower rate of Gly metabolism in CMSII leaves in the dark, the Gly to Ser ratio in the light displayed a similar dependence on photosynthesis to the WT. It is concluded that: (a) Mitochondrial complex I is required for optimal photosynthetic performance, despite the operation of alternative dehydrogenases in CMSII; and (b) complex I is necessary to avoid redox disruption of photosynthesis in conditions where leaf mitochondria must oxidize both respiratory and photorespiratory substrates simultaneously.     

Oryza sativa Chloroplast Signal Recognition Particle 43 (OscpSRP43) Is Required for Chloroplast Development and Photosynthesis

A rice chlorophyll-deficient mutant w67 was isolated from an ethyl methane sulfonate (EMS)–induced IR64 (Oryza sativa L. ssp. indica) mutant bank. The mutant exhibited a distinct yellow-green leaf phenotype in the whole plant growth duration with significantly reduced levels of chlorophyll and carotenoid, impaired chloroplast development and lowered capacity of photosynthesis compared with the wild-type IR64. Expression of a number of genes associated with chlorophyll metabolism, chloroplast biogenesis and photosynthesis was significantly altered in the mutant. Genetic analysis indicated that the yellow-green phenotype was controlled by a single recessive nuclear gene located on the short arm of chromosome 3. Using map-based strategy, the mutation was isolated and predicted to encode a chloroplast signal recognition particle 43 KD protein (cpSRP43) with 388 amino acid residuals. A single base substitution from A to T at position 160 resulted in a premature stop codon. OscpSRP43 was constitutively expressed in various organs with the highest level in the leaf. Functional complementation could rescue the mutant phenotype and subcellular localization showed that the cpSRP43:GFP fusion protein was targeted to the chloroplast. The data suggested that Oryza sativa cpSRP43 (OscpSRP43) was required for the normal development of chloroplasts and photosynthesis in rice.     

Contribution of Gamma amino butyric acid (GABA) to salt stress responses of Nicotiana sylvestris CMSII mutant and wild type plants

Plants accumulate high levels of Gamma amino butyric acid (GABA) in response to different environmental stresses and GABA metabolism has different functions such as osmotic and pH regulation, bypass of tricarboxylic acid cycle, and C:N balance. The cytoplasmic male sterile (CMS) II mutant of Nicotiana sylvestris has a deletion in the mitochondrial gene nad7 which encodes the NAD7 subunit of complex I which causes increased leaf respiration, impaired photosynthesis, slower growth and increased amino acid levels. In this study we aimed to elucidate the role of GABA and GABA metabolism in different genotypes of the same plant system under salt stress (100mM NaCl) in short (24h) and long (7, 14 and 21 days) terms. We have investigated the differences in leaf fresh and dry weights, relative water content, photosynthetic efficiency (F(v)/F(m)), glutamate dehydrogenase (GDH, EC 1.4.1.4) and glutamate decarboxylase (GAD, EC 4.1.1.15) enzyme activities, GABA content and GAD gene expression profiles. GDH activity showed variations in CMSII and wild type (WT) plants in the first 24h. GAD gene expression profiles were in good agreement with the GAD enzyme activity levels in CMSII and WT plants after 24h. In long-term salinity, GAD activities increased in WT but, decreased in CMSII. GABA accumulation in WT and CMSII plants in short and long term was induced by salt stress. Variations in GDH and GAD activities in relation to GABA levels were discussed and GABA metabolism has been proposed to be involved in better performance of CMSII plants under long term salinity.     

Reduction in chlorophyll content without a corresponding reduction in photosynthesis and carbon assimilation enzymes in yellow-green oil yellow mutants of maize

The photosynthetic properties of a yellow lethal mutant, Oy/oy, and two yellow-green mutants of maize which are allelic (a homozygous recessive oy/oy and a heterozygous dominant Oy/+) were examined. Although Oy/oy had little or no chlorophyll or capacity for CO₂ fixation compared to normal siblings, it had 28% as much ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco) activity, and from 40% to near normal activities of C₄ cycle enzymes.Both yellow-green mutants had only half as much chlorophyll per leaf area as normal green seedlings in greenhouse-grown plants in winter and spring. However, the absorbance of light by the mutants was relatively high, as their transmittance was only 5 to 8% greater than normal leaves. In winter-grown greenhouse plants, the activities of Rubisco and several C₄ cycle enzymes in the mutants were unaffected and similar to those of normal seedlings on a leaf area basis. After allowing for small differences in leaf absorbance, the light response curves for photosynthesis in the mutants were similar on a leaf area basis but much higher on a chlorophyll basis than those of the normal seedlings. In spring-grown greenhouse plants the enzyme activities and photosynthesis rates were about 30% lower per leaf area in the yellow-green mutant leaves compared to the wild type. The maximum carboxylation efficiency (measured under low CO₂ and 1000 mol quanta m^-2 s^-1) in the mutants and normal leaves was similar on a Rubisco protein basis. The results indicate that maize can undergo a 50% reduction in chlorophyll content without a corresponding reduction in enzymes of carbon assimilation, and still maintain a high capacity for photosynthesis.Abbreviations Chl chlorophyll - PEP phosphoenolypruvate - Rubisco ribulose-1,5-bisphosphate carboxylase oxygenase This research was supported by CSIRO and by USDA Competitive Grant 86-CRCR-1-2036.     

Pigments and Gas Exchange Characteristics in Leaves of Chlorophyll Mutants of Pisum sativum

Quantitative and qualitative characteristics of pigment composition and gas exchange were studied in chlorophyll mutants of pea, Pisum sativum L.: chlorotica 2004 and 2014. The mutant 2004 had light-green color, whereas the mutant 2014 has yellow-green leaves and stems; they contained about 80 and 50% of chlorophyll, respectively, compared to the initial line. cv. Torsdag. Leaves of the mutant 2004 had significantly lower carotene content and accumulated more lutein and violaxanthin. In the mutant 2014, the contents of chlorophyll and all carotenoids were reduced almost proportionally. The quantum efficiency of photosynthesis was by 29–30% lower in the mutants, and it was 1.5–2 times higher in F₁ hybrids, as compared to control plants. Our data allow us to conclude that the impairment of photosynthesis in the mutant 2014 is caused by the changed mesostructure of leaves, whereas in the mutant 2004, it may be caused by an impairment of photosystem reaction centers.     

Proteomics Study of COI1-regulated Proteins in Arabidopsis Flower

Jasmonates (JAs) are a new class of plant hormone that regulate expression of diverse genes to mediate various plant responses. The Arabidopsis F-box protein COM is required for plant defense and male fertility in JA signal pathway. To further investigate the regulatory role of COM in male fertility, we compared the proteomics profiles of Arabidopsis wild type (WT) flowers with coi1-1 mutant male-sterile flowers using two-dimensional difference gel electrophoresis coupled with matrix-assisted laser desoption/ionization-time-of-flight mass spectrometry. Sixteen proteins with potential function in specific biological processes such as metabolism processes and defense/stress responses were differentially expressed in WT and coi1-1 mutant flowers. Verification on a phi class glutathione transferase AtGSTF9, one out of these 16 identified proteins, revealed that the expression of AtGSTF9 was severely downregulated in flowers of coi1-1 mutant compared with that of WT. Further function analyses of these genes would provide new insights into the molecular basis of COI1-regulated male fertility.     

小麦突变体返白系生长后期某些生理变化

返白过程之后,返白系随着叶色的复绿,植株的代谢机能开始恢复,叶绿素含量上升,光合作用增强,叶片内可溶性糖含量上升,呼吸速率高于其祖先矮变１号;复绿初期返白系气孔阻力高于矮交１号,蒸腾速率则低于矮变１号。复绿后,以上各项指标都逐渐变化,达到矮变１号的水平。之后,返白系的蒸腾速率高于矮变１号,气孔阻力低于矮变１号,叶绿素含量及光合速率均高于矮变１号,近白系和矮变互号的呼吸速率在５月９～２５日间有上升趋势,但近白系呼吸速率较高。在生长后期,返白系的根系有向土壤深层分布的趋势。分析认为返白系在生长后期有一个补偿性生长阶段,通过改善植株水分状况,提高同化能力,降低消耗来保证生长和结实的需要。     

Photosynthesis, Ribulose-1,5-bisphosphate Carboxylase, Electron Transport, and Ribulose 1,5-Bisphosphate of Virescent and Normal Green Wheat Leaves

CO₂ gas exchange, ribulose-1,5-bisphosphate, and electron transport have been measured in leaves of a yellow-green mutant of wheat (Triticum durum var Cappelli) and its wild type strain grown in the field. All these parameters, expressed on leaf area basis, were similar in both genotypes except electron transport which was more than double in the wild type. These results, treated according to a recent photosynthesis model for C₃ plants, seem to indicate that the electron transport rate of mutant leaves is not sufficient to support the carboxylation derived through both the assimilation rate and the in vitro ribulose-1,5-bisphosphate carboxylase activity. It is suggested that under our experimental conditions photosynthetic electron transport is not the sole energy-dependent determinant of ribulose-1,5-bisphosphate regeneration in the mutant.     

Photosynthetic characteristics of a new yellow-green mutant with high photosynthetic rate in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Contents of chlorophylls and carotenoids in yellow-green mutant Biao 810S were approximately half those in control type 810S. Biao 810S had fewer grana lamellae and looser structure than 810S, lower volume of starch granules in chloroplasts, but under high temperature and high irradiance the net photosynthetic rate (P _N) of Biao 810S was higher than that of 810S. The chlorophyll fluorescence parameter F_v/F_m of Biao 810S was little higher and photochemical quenching q_P was obviously higher than those of 810S. No significant differences in P _N and biomass were observed in their hybrid combination. The yellow-green mutant phenotype may be a useful genetic marker of P(T)GMS rice used for hybrid seed production.     

Defective etioplasts observed in variegation mutants may reveal the light-independent regulation of white/yellow sectors of Arabidopsis leaves

Leaf variegation resulting from nuclear gene mutations has been used as a model system to elucidate the molecular mechanisms of chloroplast development. Since most variegation genes also function in photosynthesis, it remains unknown whether their roles in photosynthesis and chloroplast development are distinct. Here, using the variegation mutant thylakoid formation1 (thf1) we show that variegation formation is light independent. It was found that slow and uneven chloroplast development in thf1 can be attributed to defects in etioplast development in darkness. Ultrastructural analysis showed the coexistence of plastids with or without prolamellar bodies (PLB) in cells of thf1, but not of WT. Although THF1 mutation leads to significant decreases in the levels of Pchlide and Pchllide oxidoreductase (POR) expression, genetic and 5-aminolevulinic acid (ALA)-feeding analysis did not reveal Pchlide or POR to be critical factors for etioplast formation in thf1. Northern blot analysis showed that plastid gene expression is dramatically reduced in thf1 compared with that in WT, particularly in the dark. Our results also indicate that chlorophyll biosynthesis and expression of plastidic genes are coordinately suppressed in thf1. Based on these results, we propose a model to explain leaf variegation formation from the plastid development perspective.     

Dissecting the molecular basis of the contribution of source strength to high fructan accumulation in wheat

Fructans represent the major component of water soluble carbohydrates (WSCs) in the maturing stem of temperate cereals and are an important temporary carbon reserve for grain filling. To investigate the importance of source carbon availability in fructan accumulation and its molecular basis, we performed comparative analyses of WSC components and the expression profiles of genes involved in major carbohydrate metabolism and photosynthesis in the flag leaves of recombinant inbred lines from wheat cultivars Seri M82 and Babax (SB lines). High sucrose levels in the mature flag leaf (source organ) were found to be positively associated with WSC and fructan concentrations in both the leaf and stem of SB lines in several field trials. Analysis of Affymetrix expression array data revealed that high leaf sucrose lines grown in abiotic-stress-prone environments had high expression levels of a number of genes in the leaf involved in the sucrose synthetic pathway and photosynthesis, such as Calvin cycle genes, antioxidant genes involved in chloroplast H₂O₂ removal and genes involved in energy dissipation. The expression of the majority of genes involved in fructan and starch synthetic pathways were positively correlated with sucrose levels in the leaves of SB lines. The high level of leaf fructans in high leaf sucrose lines is likely attributed to the elevated expression levels of fructan synthetic enzymes, as the mRNA levels of three fructosyltransferase families were consistently correlated with leaf sucrose levels among SB lines. These data suggest that high source strength is one of the important genetic factors determining high levels of WSC in wheat.     

Characterization and gene mapping of a chlorophyll-deficient mutant clm1 of Triticum monococcum L.

Diploid wheat Triticum monococcum L. is a model plant for wheat functional genomics. Chlorophyll-deficient mutant (clm1) was identified during manual screening of the ethyl methanesulphonate (EMS)-treated M₂ progenies of T. monococcum accession pau14087 in the field. The clm1 mutant, due to significantly decreased chlorophyll content compared with the wild-type (WT), exhibited pale yellow leaves which slowly recovered to green before flowering. The clm1 mutant showed early flowering, reduced number of tillers, trichome length and density, and different shape as compared with the WT. At the same time, clm1 mutant culm had more chlorophyll-containing parenchymatous tissues compared to WT, presumably to absorb more sunlight for photosynthesis. Genetic analysis indicated that the clm1 mutation was monogenic recessive. The clm1 mutant was mapped between Xgwm473 and Xwmc96 SSR markers, with genetic distances of 2.1 and 2.6 cM, respectively, on the 7A^mL chromosome.     

组蛋白去乙酰化酶抑制剂(HDACi)对小麦基因编辑效率的影响及转录组学分析

主要研究组蛋白去乙酰化酶抑制剂(HDACi)与染色质状态以及CRISPR/Cas9的编辑效率之间的关系。利用不同浓度的尼克酰胺(0,2.5和5 mmol/L)和丁酸钠(0,5和10 mmol/L)对小麦幼苗处理7 d和14 d,结果显示丁酸钠处理会抑制幼苗的生长,而尼克酰胺对幼苗影响较小。对尼克酰胺处理的小麦幼苗进行转录组测序,发现了一些有利于促进染色质状态开放的基因:6个甲基转移酶合成通路基因。此外对未发生编辑的TaAGO4a基因编辑转基因小麦材料的T2代进行尼克酰胺处理,结果显示5 mmol/L处理14 d时检测到1株3A和3B基因组均杂合编辑的植株,编辑效率从0提高到8.3%,其它处理组和对照组均没有检测到编辑。本研究证明尼克酰胺确实可以提高小麦基因编辑效率,为提高小麦基因编辑效率提供了一种新策略。     

小麦叶绿体蛋白质编码基因RNA编辑位点的测定及与返白现象的关系

RNA编辑是一种转录后基因加工修饰现象,广泛存在于高等植物细胞器中。已有研究表明,RNA编辑与植物发生白化或者黄化有关。通过PCR、RT-PCR及测序的方法,对具有阶段性白化特性的小麦（Triticum aestivum）返白系FA85及其野生型矮变一号（Aibian 1）的叶绿体蛋白质编码基因RNA编辑位点进行了测定,在14个基因上发现了26个编辑位点。有5个编辑位点在2个株系之间存在编辑效率的差异,且这些差异的位点均位于编码叶绿体RNA聚合酶的基因上,其中3个位点编辑前后对应的蛋白质二级结构可能有差异。对2个株系叶绿体中PEP、NEP及PEP、NEP共同依赖基因转录水平的检测显示,除psbA和clpP外,其它基因在小麦返白系中的转录水平均有不同程度的下降。这种转录水平的显著下降及叶绿体RNA聚合酶基因上RNA编辑位点编辑效率的改变,可能与小麦返白系叶片的返白有关。     

Photorespiratory metabolism and nodule function: behavior of Lotus japonicus mutants deficient in plastid glutamine synthetase

Two photorespiratory mutants of Lotus japonicus deficient in plastid glutamine synthetase (GS(2)) were examined for their capacity to establish symbiotic association with Mesorhizobium loti bacteria. Biosynthetic glutamine synthetase (GS) activity was reduced by around 40% in crude nodule extracts from mutant plants as compared with the wild type (WT). Western blot analysis further confirmed the lack of GS(2) polypeptide in mutant nodules. The decrease in GS activity affected the nodular carbon metabolism under high CO(2) (suppressed photorespiration) conditions, although mutant plants were able to form nodules and fix atmospheric nitrogen. However, when WT and mutant plants were transferred to an ordinary air atmosphere (photorespiratory active conditions) the nodulation process and nitrogen fixation were substantially affected, particularly in mutant plants. The number and fresh weight of mutant nodules as well as acetylene reduction activity showed a strong inhibition compared with WT plants. Optical microscopy studies from mutant plant nodules revealed the anticipated senescence phenotype linked to an important reduction in starch and sucrose levels. These results show that, in Lotus japonicus, photorespiration and, particularly, GS(2) deficiency result in profound limitations in carbon metabolism that affect the nodulation process and nitrogen fixation.     

Zea3: a pleiotropic mutation affecting cotyledon development, cytokinin resistance and carbon-nitrogen metabolism

When photomorphogenesis takes place during early plant development, the cotyledons undergo a metabolic transition from heterotrophic sink metabolism to autotrophic source metabolism. A mutant screen was devised for seedlings affected in the regulation of nitrate assimilation during this early sink-source transition in Nicotiana plumbaginifolia. A mutant (EMS 203.6) was isolated for its inability to grow on low nitrate concentration. In contrast to wild-type (WT) plants, the mutant cotyledons remained tightly attached to each other throughout seedling development. It was found that a low carbon/nitrogen ratio (C/N ratio) in the medium was required for mutant growth. The higher the ratio was, the more the growth was inhibited. Mutant EMS 203.6 accumulated all amino acids in permissive conditions (low C/N ratio), and all amino acids and sugars also in selective (high C/N ratio) conditions. In addition, sucrose in the medium repressed light-regulated genes involved in nitrate assimilation and in photosynthesis in the mutant but not in the WT plants. The mutation was mapped to the Zea3 complementation group which confers resistance to zeatin. This zeatin resistance was associated with a hypertrophy of mutant cotyledons in response to cytokinin. Both cytokinin resistance and sensitivity to a high C/N ratio were not observed in etiolated mutant seedlings and were restricted to the jointed-cotyledon developmental stage. Previous physiological studies showed evidence for a role of cytokinins in the expression of nitrate reductase. Here, the first genetic evidence for a link between carbohydrate/nitrogen metabolism and cytokinin action during early development is provided.