Metabolism of nicotinamide, adenine and inosine in developing microspore-derived canola (Brassica napus) embryos

The metabolic fate of [carbonyl-(14)C]nicotinamide, [8-(14)C]adenine and [8-(14)C]inosine was examined in microspore-derived canola (Brassica napus) embryos at different developmental stages: globular stage (day 10, stage 1), early cotyledonary stage (day 20, stage 2), late cotyledonary stage (day 25, stage 3), and fully developed stage (day 35, stage 4). Uptake of [8-(14)C]nicotinamide by the embryos was always rapid. A lower uptake rate was found for [8-(14)C]adenine and [8-(14)C]inosine, especially at stages 1 and 2. [Carbonyl-(14)C]nicotinamide was converted to nicotinic acid and further metabolized to pyridine nucleotides (NAD/NADP). Some radioactivity was also associated to nicotinic acid glucoside. [8-(14)C]adenine was efficiently utilized for the synthesis of adenine nucleotides and RNA. A small fraction of adenine was degraded to CO(2) via ureides. Up to 40% of [8-(14)C]inosine was salvaged to nucleotides and RNA, although degradation of [8-(14)C]inosine to CO(2) was pronounced. At stage 1, highest salvage activities of nicotinamide, adenine and inosine were observed. In contrast, the lowest purine salvage and highest purine catabolism were found in stage 3 embryos. These results suggest that both nicotinamide and purine salvage for NAD/NADP and purine nucleotides synthesis are extremely high in the globular stage (stage 1). These activities decrease gradually until the late cotyledonary stage (stage 3), before increasing again in the fully developed embryos (stage 4). Overall it appears that nicotinamide and purine salvage are required in support of active growth during the initial phases of embryogenesis and at the end of the maturation period, in preparation for post-embryonic growth.     

Growth and physiological responses of canola (Brassica napus) to UV-B and CO2 under controlled environment conditions

Few studies have investigated the interaction of ultraviolet (UV)-B radiation and CO₂ concentration on plants. We studied the combined effects of UV-B radiation and CO₂ concentration on canola ( Brassica napus cv. 46A65) under four growth conditions – ambient CO₂ with UV-B (control), elevated CO₂ with UV-B, ambient CO₂ without UV-B, and elevated CO₂ without UV-B – to determine whether the adverse effects of UV-B are mitigated by elevated CO₂. Elevated CO₂ significantly increased plant height and seed yield, whereas UV-B decreased them. Elevated CO₂ ameliorated the adverse effects of UV-B in plant height. UV-B did not affect the physical characteristics of leaf but CO₂ did. Certain flower and fruit characteristics were affected negatively by UV-B and positively by CO₂. UV-B did not affect net photosynthesis, transpiration and stomatal conductance but decreased water use efficiency (WUE). Elevated CO₂ significantly increased net photosynthesis and WUE. Neither UV-B nor CO₂ affected chlorophyll (Chl) fluorescence. UV-B significantly decreased Chl b and increased the ratio of Chl a / b . Elevated CO₂ decreased only the ratio of Chl a / b . UV-B significantly increased UV-absorbing compounds while CO₂ had no effect on them. Both UV-B and CO₂ significantly increased epicuticular wax content. Many significant relationships were found between morphological, physiological, and chemical parameters. This study showed that elevated CO₂ can partially ameliorate some of the adverse effects of UV-B radiation in B . napus .     

Fatty acid composition in microspore-derived secondary embryos of Brassica napus L.

Fatty acid (FA) composition was determined in secondary embryos (SeEs) of Brassica napus L. of the cv. ‘Topas’ and ‘Janetzki’, and compared with the FA composition in microspore-derived embryos (MDEs) and seeds. SeEs of ‘Topas’, a rapessed cultivar with low erucic acid, revealed the same FA composition as observed in the MDEs. The FA pattern was, in most of the cases, independent of the procedures used for induction of SeEs e.g. low density cultures, transversal wounding, auxin treatment, and light conditions. However, non-embryogenic calli, as well as leaves from greenhouse- and in vitro-grown material had a FA composition distinctly different from the MDEs or SeEs. SeEs with an abnormal phenotype revealed differences in FA composition compared to MDEs or SeEs, but was distinct from the composition of non-embryogenic tissues. Virtually no erucic acid (22:1) or eicosaenoic acid (20:1) could be detected in SeEs of ‘Topas’. However, its presence in SeEs of ‘Janetzki’, a high erucic acid rapeseed cultivar, demonstrates that SeEs contain embryo-specific FAs. Under standard culture conditions, the levels of 22:1 and 20:1 were the same as observed in MDEs, which was approximately half the content observed in the seeds. The similarity in FA composition between SeEs and MDEs, of both low and high erucic acid rapeseed cultivars, is a unique characteristic which differs from most other somatic embryogenic systems.     

Oligochitosan induced Brassica napus L. production of NO and H2O2 and their physiological function

NO (nitric oxide) and H₂O₂ (hydrogen peroxide) are important signaling molecule in plants. Brassica napus L. was used to understand oligochitosan inducing production of NO (nitric oxide) and H₂O₂ (hydrogen peroxide) and their physiological function. The result showed that the production of NO and H₂O₂ in epidermal cells of B. napus L. was induced with oligochitosan by fluorescence microscope. And it was proved that there was an interaction between NO and H₂O₂ with L-NAME (N^G-nitro-l-arg-methyl eater), which is an inhibitor of NOS (NO synthase) in mammalian cells that also inhibits plant NO synthesis, and CAT (catalase), which is an important H₂O₂ scavenger, respectively. It was found that NO and H₂O₂ induced by oligochitosan took part in inducing reduction in stomatal aperture and LEA protein gene expression of leaves of B. napus L. All these results showed that oligochitosan have potential activities of improving resistance to water stress.     

甘蓝型油菜BnCYP78A8的克隆及序列分析

采用Genome walking方法,首次克隆到甘蓝型油菜BnCYP78A8的基因组序列,根据基因特异性引物克隆到其编码序列。基因组序列长1 679bp,有1个内含子和2个外显子。编码序列长1 605bp,编码534个氨基酸。序列比对分析表明,其氨基酸序列与拟南芥细胞色素P450单加氧酶基因(AtCYP78A8)的相似度高达88%。生物信息学分析显示,该蛋白含有1个细胞色素P450特有的亚铁血红素配合基结合位点和1个跨膜结构域。实时荧光定量PCR分析结果表明,BnCYP78A8在甘蓝型油菜的各个器官组织均有表达,根中表达量最高,表明该基因可能参与根的生长发育。     

甘蓝型油菜雄性不育系160S育性转换与利用

以甘蓝型油菜雄性不育系160S为试验材料,分别在自然栽种和人工控温条件下对其花器官形态变化、花粉育性转换和杂种优势等进行了初步研究,以探讨植物温敏雄性不育的发生机制。结果表明:环境温度对160S的花器官形态及育性转换具有明显的作用,高温可使花瓣变小,雄蕊退化,花粉活力、角粒数与自交有效结角率降低,表现为低温可育、高温不育,育性变化趋势表现为完全可育-半不育-彻底败育。160S恢复源广泛,且具有较好的配合力和杂种优势,为利用两系法生产油菜杂交种提供了一个较好的途径。     

花期渍水逆境下氮素对油菜产量及氮肥利用效率的影响

温室盆栽试验条件下,设置渍水和对照2个水分处理,每个水分处理下设置3个施氮水平(0.05、0.2、0.3 g N·kg^-1土),研究了花后渍水逆境下氮素营养对两个氮高效基因型‘Monty’、‘湘油15’和两个氮低效基因型‘R210’、‘Bin270’油菜产量、产量性能及氮肥利用效率的影响.结果表明:与对照相比,花后渍水处理显著降低了油菜的单株角果数、千粒重、每角粒数和籽粒产量.在适宜水分条件下,增施氮肥显著增加了油菜籽粒产量,而在渍水逆境处理下,增施氮肥对油菜籽粒产量的形成贡献不大.氮高效基因型较氮低效基因型对花后渍水逆境下的籽粒灌浆充实具有一定的促进作用.在同一水分处理下,花后渍水明显降低了油菜氮肥利用率、氮肥偏生产力、氮肥农学利用率、氮素吸收效率和氮收获指数,渍水显著影响了不同基因型油菜的氮素吸收利用能力,而氮高效基因型在渍水逆境下较氮低效基因型更有利于将氮素转运、再分配到角果中,提高籽粒生产效率.油菜产量性能参数存在显著的水氮互作效应,水分、氮肥及水氮互作对油菜籽粒产量和产量性能参数的影响因基因型的不同而异.     

甘蓝型油菜RPD3/HDA1基因家族鉴定及早熟相关基因挖掘

该研究运用生物信息学方法鉴定甘蓝型油菜RPD3/HDA1基因家族,检测了其在‘黔油早2号’和‘中双11’中的表达水平及2个品种在低温(4℃)和ABA胁迫下该家族基因的表达特征,以探讨RPD3/HDA1基因在甘蓝型油菜中的潜在功能,为早熟油菜抗逆性遗传改良提供理论基础和候选基因。结果表明:(1)在甘蓝型油菜全基因组中共鉴定到28个RPD3/HDA1基因,将其命名为BnHDA1~BnHDA28,聚类为4个亚家族,同一亚家族成员的基因结构较为相似;在该基因家族中共检测到16对复制基因,均为片段重复。(2)顺式作用元件预测统计中共发现675个元件与植物激素、环境胁迫和光响应有关。(3)qRT-PCR分析显示,RPD3/HDA1基因在‘黔油早2号’中的表达量均高于‘中双11’;低温胁迫下,‘黔油早2号’和‘中双11’中RPD3/HDA1基因呈差异表达,与‘中双11’相比,RPD3/HDA1基因在‘黔油早2号’中的下调幅度较大;ABA处理后,RPD3/HDA1基因在2个品种中表达模式不一致,‘黔油早2号’中大部分RPD3/HDA1基因表达量较‘中双11’下调幅度小。研究认为,RPD3/HDA1基因可能在油菜开花中发挥调节作用,而且可能通过激素信号通路和防御信号通路参与油菜的生长发育和防御反应的调节。     

甘蓝型油菜水苏糖合成酶基因克隆及表达分析

以甘蓝型油菜品种‘德油5号’为试材,采用RT-PCR和RACE方法首次从油菜中获得水苏糖合成酶基因cDNA全长序列,命名为BnSTS,GenBank登录号为HQ285880.1。该cDNA全长3 210bp,包含一个长为2 619bp的开放阅读框,编码873个氨基酸。通过构建原核表达载体,成功表达出预期蛋白。同源性比对结果显示,该基因编码蛋白与拟南芥STS相似性最高为82.08%。荧光定量PCR结果显示,基因表达水平与油菜种子发育过程中水苏糖含量变化具有相关性,与种子脱水耐性的获得具有时间一致性。该基因可能在种子脱水耐性形成机制中具有一定的作用。     

甘蓝型油菜热激转录因子的克隆及表达分析

以甘蓝型纯系油菜为试材,用RT-PCR和RACE方法首次从油菜种子中获得油菜热激转录因子的cDNA全长序列,命名为BnHSFA4a,GenBank登录号为HQ435241。结果表明:该cDNA长1 667bp,编码1个具有389aa的蛋白质,该基因编码的氨基酸序列与拟南芥热激转录因子AtHSFA4a编码的氨基酸序列间相似度为82%。对34条编码不同热激转录因子的氨基酸序列进行多重比对,结果在100～190aa处序列间氨基酸总相似性超过60%,显示出较高的保守性。构建原核表达载体并成功表达出预期蛋白。半定量RT-PCR结果显示,该基因的表达先于油菜肌醇半乳糖苷合成酶(BnGOLS1)基因,符合该基因调控BnGOLS1的假设。推测AtHSFA4a基因可能通过调控BnGOLS1的表达量进而在油菜种子脱水耐性获得过程中发挥一定的作用。     

The density dependence of plant responses to elevated CO2

1 Stands of the annual Brassica kaber were grown at a range of six densities in both ambient and elevated CO₂ environments, and measurements of shoot growth were made from seedling emergence through to reproduction.
2 Early in stand development (21 days following emergence), CO₂ enhancement (β) for above-ground biomass was highly density-dependent, ranging from 1.41 at the lowest density (20 plants m−2) to 0.59 at the highest density (652 plants m−2).
3 As stands matured and total biomass exceeded a relatively low threshold level (<10.0 g m^{−2; c.}  20% of final yield), the density-dependence of β disappeared. Above this shoot biomass threshold, β-values remained remarkably stable (β = 0.34) across a broad range of stand biomass, independent of a stand's initial density or age.
4 Average stand-level reproductive β-values at a final harvest were very similar to biomass values (β = 0.38) and, as with biomass values at later stages, showed no apparent density-dependence.
5 These results highlight the importance of considering density and the time-course of stand development simultaneously when assessing the potential for CO₂-induced growth enhancements in plants.     

春性甘蓝型油菜BnFY34基因的克隆及序列分析

春性甘蓝型油菜杂交种由于发育期较长,极大地限制了该油菜在高寒地区的推广。为了从春性特早熟甘蓝型油菜中筛选出苗期和蕾期差异表达的基因,该研究以春性特早熟甘蓝型油菜为材料,利用cDNA-AFLP技术筛选出1个春性特早熟甘蓝型油菜苗期特异表达的基因片段,并采用RACE技术成功分离克隆了该基因,命名为BnFY34。通过对该基因的测序和生物信息学分析,发现该基因序列大小为455 bp,包含完整的开放阅读框(ORF),编码一个由71个氨基酸残基组成的蛋白,推测的蛋白质分子量为8.04 kD,理论等电点为10.25,其三级结构中含有3个α螺旋,不含β折叠。同时,将BnFY34基因与甘蓝型油菜基因组序列进行比对,结果显示BnFY34基因位于C4染色体上,由3个外显子和2个内含子组成。另外,通过对该基因与其他植物同源基因的亲缘关系进行了分析,结果表明BnFY34基因与芸薹属植物属于同一亚族,并且与甘蓝型油菜中已报到的未诠释基因XM_013837282.1的相似度达100%,其功能有待进一步研究。该研究结果对春油菜产量和品质的早熟转基因育种具有重要意义。     

油藏环境中CO_2生物固定与转化及资源化利用

利用微生物将油藏环境中的CO2原位转化为甲烷,在完成封存的同时实现CO2生物固定与转化,进一步提高油气采收率,延长油田开发寿命,是当前研究的前沿课题。综述了CO2封存对油藏环境的影响、油藏环境CO2生物固定与转化的菌群结构与功能、转化反应热力学与动力学等方面的最新研究进展,讨论了油藏环境CO2生物固定与转化的途径及资源化利用的潜力,提出了该领域进一步的研究方向。     

Changes in CH4 and CO2 emissions from soils under flooded conditions after being exposed to FACE (free-air CO2 enrichment) for three years

To evaluate the variations of CO₂ and CH₄ emissions from FACE (free-air CO₂ enrichment, F) soils three years after rice-wheat rotation FACE treatment, incubation experiments in the laboratory with laboratory and elevated CO₂ concentration (1000 μl L?1) were carried out under flooded conditions at 25°C. Results show that soil organic carbon is increased by 11% after exposure to FACE treatment for three years. The results indicate that at laboratory and elevated CO₂, the cumulative CO₂ emissions from FACE soils are 35% and 22% higher than those from the ambient soils, whereas the cumulative CH₄ emissions from FACE soils are 2.6 and 2.3 times that of ambient soils. Thus, there is a larger ratio of cumulative emissions of CH₄ to CO₂ in the soil F. The elevated CO₂ concentration during the incubation stimulates the cumulative CO₂ emission significantly, but its stimulation on CH₄ emission is not statistically significant. The results indicate that the elevated atmospheric CO₂ concentration stimulates the turnover rates of soil organic matter, with a net increase in soil organic matter content, and alters the CH₄/CO₂ ratio.     

Changes in CH4 and CO2 emissions from soils under flooded conditions after being exposed to FACE (free-air CO2 enrichment) for three years

To evaluate the variations of CO₂ and CH₄ emissions from FACE (free-air CO₂ enrichment, F) soils three years after rice-wheat rotation FACE treatment, incubation experiments in the laboratory with laboratory and elevated CO₂ concentration (1000 μl L?1) were carried out under flooded conditions at 25°C. Results show that soil organic carbon is increased by 11% after exposure to FACE treatment for three years. The results indicate that at laboratory and elevated CO₂, the cumulative CO₂ emissions from FACE soils are 35% and 22% higher than those from the ambient soils, whereas the cumulative CH₄ emissions from FACE soils are 2.6 and 2.3 times that of ambient soils. Thus, there is a larger ratio of cumulative emissions of CH₄ to CO₂ in the soil F. The elevated CO₂ concentration during the incubation stimulates the cumulative CO₂ emission significantly, but its stimulation on CH₄ emission is not statistically significant. The results indicate that the elevated atmospheric CO₂ concentration stimulates the turnover rates of soil organic matter, with a net increase in soil organic matter content, and alters the CH₄/CO₂ ratio.     

CO2增长对杉木中龄林针叶光合生理生态的影响

通过对１７ａ生杉木人工林小枝的活体测定,研究了大气ＣＯ２增长对杉木中龄林净光合、呼吸、气孔导度和水分利用效率等生理生态特性的影响。结果表明,在ＣＯ２浓度为４５μｍｏｌ／Ｌ左右时,杉木针叶净光合速率比正常大气ＣＯ２下提高１倍以卢,气孔导度和蒸速率有不同程度的降低,水分利用效率提高约１￣２倍;同时使光补偿点降低,饱和点和光抑制点提高,光量子效率提高４０％￣２９５％且阳酝 大于阴枝,针叶暗呼吸降低２０％     

空气CO2增高条件下荔枝叶片光合作用和超氧自由基产率

研究结果表明,生长在77±5PaCO₂分压下30d的荔枝幼树,其光合速率较大气CO₂分压(39.3Pa)下的低23%,光下线粒体呼吸速率和不包含光下呼吸的CO₂补偿点亦略有降低.空气CO₂增高使叶片最大羧化速率(V_cmax)和最大电子传递速率(J_max)降低,表明大气增高CO₂分压下叶片的光系统I(PSI)能量水平较低,叶片超氧自由基产率亦降低39%,叶片感染荔枝霜疫霉病率则从生长在大气CO₂分压下的1.8%增至9.5%.可能较低光合和呼吸代谢诱致较低的超氧自由基产率,而使叶片易受病害侵染.叶片受病害侵染后表现为超氧自由基的激增.在全球大气CO₂分压增高趋势下须加强对荔枝霜疫霉病的控制.     

CO2 uptake and fluorescence responses for a shade-tolerant cactus Hylocereus undatus under current and doubled CO2 concentrations

Hylocereus undatus (Haworth) Britton and Rose growing in controlled environment chambers at 370 and 740 μmol CO₂ mol^?1 air showed a Crassulacean acid metabolism (CAM) pattern of CO₂ uptake, with 34% more total daily CO₂ uptake under the doubled CO₂ concentration and most of the increase occurring in the late afternoon. For both CO₂ concentrations, 90% of the maximal daily CO₂ uptake occurred at a total daily photosynthetic photon flux density (PPFD) of only 10 mol m^?2 day^?1 and the best day/night air temperatures were 25/15°C. Enhancement of the daily net CO₂ uptake by doubling the CO₂ concentration was greater under the highest PPFD (30 mol m^?2 day^?1) and extreme day/night air temperatures (15/5 and 45/35°C). After 24 days of drought, daily CO₂ uptake under 370 μmol CO₂ mol^?1 was 25% of that under 740 μmol CO₂ mol^?1. The ratio of variable to maximal chlorophyll fluorescence (F_y/F_m) decreased as the PPFD was raised above 5 mol m^?2 day^?1, at extreme day/night temperatures and during drought, suggesting that stress occurred under these conditions. F_v/F_m was higher under the doubled CO₂ concentration, indicating that the current CO₂ concentration was apparently limiting for photosynthesis. Thus net CO₂ uptake by the shade-tolerant H. undatus, the photosynthetic efficiency of which was greatest at low PPFDs. showed a positive response to doubling the CO₂ concentration, especially under stressful environmental conditions.