烟草叶片发育过程中光合功能衰退与H2O2积累的关系

以烟草（Nicotiana tabacum L．cv NC89）为材料,研究了叶片发育过程中H2O2积累与叶绿体光合功能衰退、抗坏血酸-谷胱甘肽（AsA—GSH）循环的关联。结果表明,光合功能衰退过程中,各光合参数均表现为先缓慢后快速的下降趋势,核酮糖-1,5-二磷酸羧化酶（RuBPCase）活性下降较电子传递活性下降迅速,H2O2含量与叶绿素含量、光合速率、RuBPCase活性、抗坏血酸过氧化物酶（APX）、谷胱甘肽还原酶（GR）活性显著负相关。H2O2的定位染色也证实光合功能衰退与H2O2积累密切相关。APX和GR在光合功能可逆衰退阶段维持较高水平,不可逆衰退阶段下降稍快。烟草叶片光合功能衰退快于AsA—GSH循环运转的下调。     

扬麦5号旗叶光合功能衰退进程中光合膜特性的变化

旗叶自然衰退过程中光合膜特性变化的结果表明,光合功能高值持续期类囊体膜电子传递活性均维持较高水平,多肽组分也维持相对稳定;进入光合功能的速降期后,活性呈快速下降趋势,类囊体膜小分子多肽等组分均出现不同降解。旗叶全展后叶绿体ＡＴＰ含量在高值持续期维持一定水平;进入速降期后,对应于光合膜电子传递活性及Ｐ／Ｏ值,叶绿体ＡＴＰ含量变化存在“滞后”的现象;强光逆境下,速降期类囊体电子传递活性受抑制程度比高值     

烟草叶片发育过程中光合功能衰退与H_2O_2积累的关系

以烟草(NicotianatabacumL.cvNC89)为材料,研究了叶片发育过程中H2O2积累与叶绿体光合功能衰退、抗坏血酸-谷胱甘肽(AsA-GSH)循环的关联。结果表明,光合功能衰退过程中,各光合参数均表现为先缓慢后快速的下降趋势,核酮糖-1,5-二磷酸羧化酶(RuBPCase)活性下降较电子传递活性下降迅速,H2O2含量与叶绿素含量、光合速率、RuBPCase活性、抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)活性显著负相关。H2O2的定位染色也证实光合功能衰退与H2O2积累密切相关。APX和GR在光合功能可逆衰退阶段维持较高水平,不可逆衰退阶段下降稍快。烟草叶片光合功能衰退快于AsA-GSH循环运转的下调。     

遮荫条件下草莓的光合持性变化

对宝交早生和硕丰两个草莓品种遮荫处理后测定其光合特性变化结果表明,遮荫处理使两个草莓品种叶片光合速率显著降低,分别下降了20％和47％,而表观量子效率分别提高了13％和8％,叶片中叶绿素含量升高而可溶性蛋白含量显著降低,光系统II电子传递活笥（PSII活性）分别下降了22．5％和53．7％,1,5二磷酸核酮糖羧化酶（Rubisco)活性分别低了19．6％和35．3％,进一步讨论了草莓光饱和速率下降的生理基础。     

遮荫条件下草莓的光合特性变化

对宝交早生和硕丰两个草莓品种遮荫处理后测定其光合特性变化结果表明,遮荫处理使两个草莓品种叶片光合速率显著降低,分别下降了20%和47%,而表观量子效率分别提高了13%和8%.叶片中叶绿素含量升高而可溶性蛋白含量显著降低.光系统Ⅱ电子传递活性(PSⅡ活性)分别下降了22.5%和53.7%.1,5二磷酸核酮糖羧化酶(Rubisco)活性分别降低了19.6%和35.3%.进一步讨论了草莓光饱和速率下降的生理基础.     

外源海藻糖对PEG渗透胁迫下小麦Rubisco及其活化酶的影响

以抗旱品种‘晋麦47’和干旱敏感品种‘郑引1号’为材料,通过室内水培试验研究了外源海藻糖对PEG渗透胁迫下小麦叶片净光合速率、1,5-二磷酸核酮糖羧化酶/加氧酶(Rubisco)和1,5-二磷酸核酮糖羧化酶/加氧酶活化酶(RCA)含量和相关基因表达特性的影响。结果表明:(1)外源海藻糖和渗透胁迫均能显著增加2个小麦品种叶片海藻糖含量。(2)渗透胁迫显著降低了2个品种小麦叶片的净光合速率,而外源海藻糖能显著缓解受胁迫小麦叶片净光合速率的降低幅度。(3)渗透胁迫仅使‘郑引1号’Rubisco大亚基基因(rbcL)相对表达量及相应蛋白含量显著降低;渗透胁迫显著降低了小麦RCAα和β亚基基因相对表达量,并显著降低RCA蛋白含量,而外源海藻糖不能缓解RCA蛋白含量的降低;渗透胁迫显著降低了Rubisco总活性、初始活性、活化状态及RCA活性,而外源海藻糖则能显著缓解上述酶活性的下降。(4)小麦叶片净光合速率与其rbcL、RCAα和β亚基基因相对表达量及Rubisco总活性、初始活性、活化状态及RCA活性均呈极显著正相关关系。研究发现,在渗透胁迫条件下,外源海藻糖主要从翻译后层面对小麦叶片Rubisco和RCA的活性发挥显著保护作用,从而缓解了小麦净光合速率的降低。     

不同发育时期追施氮肥对冬小麦旗叶中光合酶活性的影响

小麦开花后,随着旗叶的衰老,旗叶中1,5-二磷酸核酮糖羧化酶（RuBPC）、磷酸烯醇式丙酮酸羧化酶（PEPC）和乙醇酸氧化酶（GO）活性呈下降趋势。随着追施氮肥时期的推迟,光合酶活性呈增加趋势,这意味着氮肥追施时间后移有利于提高小麦光合速率。在旗叶衰老后期,大穗型品种小麦旗叶中光合酶活性略高于多穗型品种小麦。     

转录后基因沉默系统研究烟草rbcS基因功能

初步建立了利用病毒载体诱导转录后基因沉默系统研究烟草(Nicotiana benthamiana)1,5-二磷酸核酮糖羧化酶／加氧酶小亚基(Ribulose-1,5-bisphosphate carboxylase／oxylase small subunit,rbcS)基因功能的模式。用携带与1,5-二磷酸核酮糖羧化酶／加氧酶小亚基基因同源的cDNA片段的烟草脆裂病毒载体(pTV．rbcS)侵染烟草(Nicotiana benthamiana),诱导内源rbcS基因沉默并在此基础上建立了研究rbcS基因功能的模式：初步进行了rbcS基因沉默后的表型分析、转录水平分析、蛋白质表达水平分析以及利用HPLC方法定量分析rbcS基因沉默后的光合色素变化。结果表明：病毒诱导基因沉默瞬时表达体系中烟草最佳侵染时期为苗龄21-24d,用于侵染的重组农杆菌的最佳浓度的OD值为1～1．5;烟草Rubisco小亚基的表达量可能调节Rubisco大亚基的表达量;烟草rbcS基因与光合作用中的光能收集无关。对rbcS基因沉默的烟草叶片及对照烟草叶片的部分重要光合作用指标分析表明,运用烟草脆裂病毒载体诱导转录后基因沉默系统研究烟草rbcS基因功能具有可行性,为进一步深入研究rbcS基因功能奠定了基础。     

川草2号老芒麦（Elymus sibiricus L.）UV-B辐射敏感基因rbcL的克隆及其调控表达研究

rbcL是编码光合关键酶1,5-二磷酸核酮糖羧化酶（Rubisco）大亚基的基因。本文运用mRNA差异显示技术（DDRT-PCR）并通过5ˊRACE (Rapid Amplification of cDNA Ends) 从高原植物川草2号老芒麦（Elymus sibiricus L. cv. 'chuancao No.2'）中获得了受增强UV-B辐射抑制的rbcL基因,该基因全长cDNA为1.51kb,开放阅读框（ORF）长1.434kb,编码477个氨基酸。氨基酸序列与Elymus trachycaulus中的Rubisco大亚基具有97％的同源性、与Triticum aestivum和Hordeum comosum的Rubisco大亚基同源性均为 98％。Northern杂交分析表明,增强UV-B辐射后6h,rbcL基因表达受到强烈抑制,处理后60h,其表达几乎完全被抑制,表明即使是长期生长在高原地区、强UV-B辐射条件下的高原物种,在受到较强的UV-B辐射后,其rbcL基因的转录也会受到抑制。     

—个新的水稻斑马叶突变（zebraleaf1）对叶绿体发育的影响（简报）

通过γ射线诱变．在水稻粳稻栽培品种9522中得到一个斑马叶突变体zebraleaf1。为了研究zl1的功能．我们对突变体进行了形态学和细胞学的分析．同时也对此基因突变以后对叶绿体发育和光合作用的影响作了评价。突变体叶片上绿色和枯白色条纹相间．叶绿素含量显著的下降。电镜显示叶绿体类囊体的排列被打乱．变得杂乱无章。这表明。Zl1突变体在叶绿体发育过程中出现障碍。zl1基因的突变使得净光合速率显著的下降。参与光合作用的一些关键蛋白．比如核酮糖1,5-二磷酸羧化酶／加氧酶（Rubisco）、Rubisco活化酶、D1蛋白、CF1β亚基的表达量也显著的下调。但是．zl1突变体对外界环境非常敏感．有时会没有表型。     

Decrease in Three Messenger RNA Species Coding for Chloroplast Proteins in Leaves of Barley Infected with Erysiphe graminis f. sp. hordei

Cloned hybridization probes have been used to investigate the effect of infection of susceptible Hordeum vulgare cv Prior by Erysiphe graminis f. sp. hordei on the abundance of host mRNAs coding for the large (LSU) and precursor to the small (SSU) subunits of ribulose 1,5-bisphosphate carboxylase/oxygenase and the rapidly metabolized 32kD thylakoid protein (32kDP). In leaf RNA preparations from control (noninoculated) plants the amount of mRNA for the LSU and SSU declined from 7 to 11 days after sowing, whereas that for the 32kDP increased over this period. Following inoculation at 6 days after sowing, the abundance of each of the mRNA species was significantly reduced below that of controls at 1, 3, and 5 days later. Results indicate that infection causes a rapid and extensive reduction in host mRNA species coding for proteins with important photosynthetic functions.     

Rapid heating of intact leaves reveals initial effects of stromal oxidation on photosynthesis

Heat stress in leaves under natural conditions is characterized by rapid fluctuations in temperature. These fluctuations can be on the order of 10 degrees C in 7 s. By using a specially modified gas-exchange chamber, these conditions were mimicked in the laboratory to analyse the biochemical response to heat spikes. The decline in ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco) activity during prolonged heat stress is generally associated with an increase in ribulose 1,5-bisphosphate (RuBP) levels. However, rapid heating caused an initial decline in RuBP which was subsequently followed by a small decline in Rubisco carbamylation. The ratio of RuBP to Rubisco sites declined from a saturating concentration to a sub-saturating concentration, providing a possible mechanism for the decarbamylation of Rubisco. If RuBP is saturating (>1.8 RuBP Rubisco site(-1)), it acts as a cap on the catalytic site and keeps Rubisco activated. Measurements of triose-phosphate levels and NADP-malate dehydrogenase activation (a stromal redox proxy) indicated that the regeneration of RuBP by the Calvin cycle was limited by the availability of redox power.     

Regulation of chlorophyll and Rubisco levels in embryonic cotyledons of Phaseolus vulgaris

While deep within the maternal tissues (pods and testa), cotyledons of the bean (Phaseolus vulgaris L.) green and the plastids differentiate as chloroplasts. At the time of seed maturation the chloroplasts dedifferentiate and the green color is lost. We have used Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) and chlorophyll to study chloroembryo development. Chlorophyll levels and Rubisco activity increase early in embryonic development then decline as the cotyledons enter the maturation phase. Rubisco accumulation follows a strong temporal pattern over the course of embryo development, and furthermore, occurs in total darkness. Therefore, accumulation of Rubisco during embryogenesis may occur in response to developmental signals. In embryos developed in total darkness, Rubisco accumulation was uncoupled from chlorophyll accumulation. Exposure of isolated cotyledons to abscisic acid (ABA) resulted in loss of chlorophyll and decline in Rubisco levels comparable to those seen in normal embryogenesis. This indicates that the decline in Rubisco in chloroembryos in vivo results from factors such as ABA that signal the onset of maturation. The results show that ABA not only enhances the accumulation of some proteins (e.g. storage proteins), but also depresses the accumulation of others during embryogeny.Abbreviations Rubisco ribulose-1,5-bisphosphate-carboxylase/oxygenase (EC 4.1.1.39) - LSU large subunit of Rubisco - SSU small subunit of Rubisco - ABA abscisic acid - FW fresh weight     

Heterogeneity of alkaline small subunits of ribulose 1,5 bisphosphate carboxylase-oxygenase from Medicago sativa and M. falcata

The isolated leaf proteins of lucerne (Medicago sativa L. and M. falcata L.) were fractionated by Sepharose 6B column chromatography. Analysis of fractionated proteins indicated that the 2nd peak component was almost entirely ribulose 1,5 bisphosphate carboxylase-oxygenase (Rubisco) which represented 57% of the total recovered protein.Rubisco yielded one large subunit (LSU) and one small subunit (SSU) polypeptide after SDS gel electrophoresis.Isoelectric focusing of the SSU of Rubisco from genotypes of M. sativa cv. Hunter River (HR), Hairy Peruvian (HP) and of M. falcata (MF) showed two SSU components for HR and HP, and three components for MF. Most components of genotypes were located in the alkaline region of the gel. While the pIs of the SSU components of HR and HP were identical they differed from those of the SSU of MF thus demonstrating heterogeneity for SSU in Medicago.It is suggested that the alkaline nature of SSU may have some adaptive physiological significance.Abbreviations Rubisco ribulose bisphosphate 1,5-carboxylase-oxygenase - LSU large subunit - SSU small subunit - HR Hunter River - HP Hairy Peruvian - MF Medicago falcata - SDS Sodium dodecyl sulphate - TCA trichloracetic acid     

Thylakoid membrane responses to moderately high leaf temperature in Pima cotton

Photosynthesis is inhibited by high temperatures that plants are likely to experience under natural conditions. Both increased thylakoid membrane ionic conductance and ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) deactivation have been suggested as the primary cause. The moderately heat‐tolerant crop Pima S‐6 cotton (Gossypium barbadense) was used to examine heat stress‐induced inhibition of photosynthesis. Previous field‐work indicated that moderate heat stress (T = 35–45 °C) is associated with very rapid leaf temperature changes. Therefore, a system was devised for rapidly heating intact, attached leaves to mimic natural field heat‐stress conditions and monitored Rubisco activation, carbon‐cycle metabolites, thylakoid ionic conductance, and photosystem I activity. As a proxy for NADPH and stromal redox status the activation state of NADP‐malate dehydrogenase (NADP‐MDH) was measured. In dark‐adapted cotton leaves, heating caused an increase in thylakoid permeability at temperatures as low as 36 °C. The increased permeability did not cause a decline in adenosine 5′‐triphosphate (ATP) levels during steady‐state or transient heating. Rapid heating caused a transient decline in ribulose 1,5‐bisphosphate without a decrease in Rubisco activation. Sustained heating caused a decline in Rubisco activation and also oxidized the stroma as judged by NADP‐MDH activation and this is hypothesized to result from increased cyclic photophosphorylation, explaining the maintenance of ATP content in the face of increased thylakoid membrane ion leakiness.