snthr-1Bao稀毛小鼠突变基因的精确定位及克隆鉴定

snthr-1Bao稀毛小鼠足本实验室培育的呈单基因隐性遗传的突变系小鼠,突变基因已被初步定位于第9号染色体末端;为了精确定位并鉴定snthr-1Bao稀毛小鼠的突变基因,将(C57BL/6Jxsnthr-1Bao)F1代互交繁殖F2代小鼠4400余只,其中稀毛小鼠1100只,并在2个微卫星、35个可能的简单序列重复标记(simple sequence repeat,SSR)及3个酶切扩增多态性序列(cleaved amplified polymorphic sequences,CAPS)标记中找到4个合适的基因组标记.利用这些标记及F2代稀毛小鼠将突变基因精确定位到第9号染色体距着丝粒117.763 kb及119.129kb之间1.367Mb的范用内,在其问的21个基因中确定Plcdl为稀毛突变的强力候选基因.通过对基因组的直接测序,发现snthr-1Bao稀毛小鼠基因组上有一个14883bp的缺失,这一缺失包含了Plcd1基因的4-15号外显子及Vill基因的10-19号外显子.推测极可能是Plcdl基因缺失导致snthr-1Bao小鼠出现稀毛表型.     

snthr^-1Bao佃彻稀毛小鼠突变基因的精确定位及克隆鉴定

snthr^-1Bao稀毛小鼠是本实验室培育的呈单基因隐性遗传的突变系小鼠,突变基因已被初步定位于第9号染色体末端;为了精确定能并鉴定snthr^-1Bao稀毛小鼠的突变基因,将（C57BL／6J×snthr^-1Bao）F1代互交繁殖F2代小鼠4400余只,其中稀毛小鼠1100只,并在2个微卫星、35个可能的简单序列重复标记（simplesequence repeat,SSR）及3个酶切扩增多态性序列（Cleaved amplified polymorphic sequences,CAPS）标记中找到4个合适的基因组标记。利用这些标记及F2代稀毛小鼠将突变基因精确定位到第9号染色体距着丝粒117．763kb及119．129kb之间1．367Mb的范围内,在其间的21个基因中确定Plcdl为稀毛突变的强力候选基因。通过对基因组的直接测序,发现snthr^-1Bao稀毛小鼠基因组上有一个14883bp的缺失,这一缺失包含了Plcdl基因的4-15号外显子及Vill基因的10—19号外显子。推测极可能是Plcdl基因缺失导致snthr^-1Bao小鼠出现稀毛表型。     

籼稻半矮秆基因sd-t(t)的遗传定位及定位区间物理距离的估计

矮秆和半矮秆基因的利用及作用机制一直是作物育种和分子遗传研究的重要内容. sd-t(t)是从籼稻矮秆材料矮泰引-2中发现的一个与sd-1不等位的新半矮秆基因.利用由矮泰引-2与无叶舌标志基因系B30杂交产生的包含474个单株的F₂群体, 将sd-t(t)基因定位在水稻第4染色体上RFLP标记R514和R1408B之间, 距R514和 R1408B的遗传距离分别为1.1和4.5 cM. 利用水稻品系IRBB56 的BAC文库构建了sd-t(t)位点的跨叠克隆群, 并确定 R514与R1408B之间的物理距离大约为147 kb, 为进一步克隆sd-t(t)基因奠定了基础.     

模拟酸雨胁迫下硅对髯毛箬竹光合特性的影响

以髯毛箬竹为试验材料,研究了模拟酸雨胁迫(pH 3.0)下硅对髯毛箬竹叶片叶绿素相对含量、光合作用日变化以及叶绿素荧光特性等的影响.结果表明:20和100 mg·L^-1 Na₂SiO₃预处理可以不同程度地抑制酸雨胁迫下髯毛箬竹叶片叶绿素含量的显著下降,且以100 mg·L^-1浓度处理效果最佳,叶绿素含量可提高22.7%,而高浓度(500 mg·L^-1)预处理则无缓解作用-酸雨胁迫下,髯毛箬竹光合“午休”现象加重,日平均净光合速率(P_n)、气孔导度(G_s)和气孔限制值(L_s)明显降低,而胞间CO₂浓度(C_i)增大,经过20～100 mg·L^-1硅预处理后,P_n、G_s、L_s不同程度增加,而C_i有所降低,且以100 mg·L^-1硅预处理效果最佳,日平均P_n增加39.2%.酸雨胁迫下,箬竹PSⅡ最大荧光(F_m)、最大光化学效率(F_v/F_m)、潜在活性(F_v/F_o)、有效光化学效率(F_v′/F_m′)、最大荧光产额(F_m′)、光化学淬灭系数(q_P)、非光化学淬灭系数(q_N)、PSII实际光化学效率(Φ_PSⅡ)降低,暗适应和光适应下的最小荧光产额F_o、F_o′ 则升高;而100 mg·L^-1硅预处理明显抑制了胁迫下各荧光参数的变化,F_v/F_m、F_v/F_o、F_v′/F_m′和Φ_PSⅡ分别增加35.2%、146.2%、55.0%和24.3%.说明外源适宜浓度硅预处理能有效地缓解酸雨胁迫导致的髯毛箬竹光合活性下降和光合系统损伤,从而提高胁迫下植物的光合能力.     

不同浓度NaCl和Na2CO3处理对菊芋幼苗光合及叶绿素荧光的影响

 以砂培菊芋(Helianthus tuberosus)幼苗作为试验材料,分别进行不同浓度NaCl (50、 100、150、200、250 mmol&;#8226;L^－1)和Na₂CO₃ (25、50、 75、100、125 mmol&;#8226;L^－1)胁迫处理,以1/2全营养液作为对照,处理7 d后研究NaCl和Na₂CO₃胁迫处理对菊芋幼苗叶片光合作用及叶绿素动力学 参数的影响。结果表明：1)在NaCl处理下,当浓度小于150 mmol&;#8226;L^－1时,增加了菊芋的叶绿素含量、净光合速率(Net photosynthetic rate, P_n)和气孔导度(Stomatal conductivity, G_s),对荧光参数PSⅡ的电子传递情况( F_m/F_o)、PSⅡ原初光能转换效率(F_v/F_m)、PSⅡ量子效率 (Actual quantum yield of PSⅡ under actinic irradiation,φPSⅡ)和光化学猝灭系数(Photochemical quenching coefficient, qP)和非 光化学猝灭系 数(Non-photochemical quenching coefficient, NPQ)没有显著影响,随着浓度的增加,各项生理指标与对照相比除了NPQ显著 增加,其余均显著降低;2)在Na₂CO₃胁迫处理下,随着Na₂CO₃浓度的增加,与对照相比菊芋幼苗叶绿素含量、P_n、G_s以及叶绿素a荧光诱导动力 学参数F_m/F_o、F_v/F_m、φPSⅡ和qP均显著降低,NPQ显著增加;3)就NaCl和Na₂CO₃相比而言,在相同Na⁺浓度情况下,处于Na₂CO₃胁迫下的菊芋 幼苗的叶绿素含量、P_n、G_s以及叶绿素a荧光诱导动力学参数F_m/F_o、F_v/F_m、φPSⅡ和qP下降幅度和NPQ的增加幅度均显著大于NaCl,这说明 NaCl和Na₂CO₃胁迫均对菊芋幼苗造成不同程度的伤害,但在相同Na⁺浓度情况下,Na₂CO₃的伤害程度大于NaCl。由此说明菊芋对盐的忍耐程度高 于碱。     

SNP标记对角膜混浊小鼠 突变相关基因的精细定位

为深入研究前期工作中以ENU诱变技术建立的遗传性角膜混浊突变系小鼠(B6-Co)的遗传机制, 利用 SNP标记对其突变基因进行精细定位, 将该品系中具有角膜混浊表型的小鼠(B6-CoP)与DBA/2小鼠(简称D2)配种得到F₁代, 再回交D2亲本品系得到F₂代, 提取F₂代角膜混浊小鼠鼠尾DNA。在MGI数据库中选取小鼠13号染色体已定位区间附近5个在C57BL/6(简称B6)和D2两个品系之间有差异的SNP, 应用聚合酶链反应-限制性片段长度多态性(PCR-RFLP)技术及连锁分析方法对B6-Co小鼠突变基因进行精细定位。结果表明: B6-Co小鼠突变基因定位于13号染色体上112 546 283~113 397 654 bp之间, 因该区间内有5个已知基因, 其中Map3k1基因与小鼠眼睛形态生成和眼睑闭合密切相关, 提示Map3k1是B6-Co小鼠突变的强力候选基因。     

不同氮素水平下二氧化碳加富对草莓叶片光抑制的影响

用便携式调制叶绿素荧光仪和光合仪研究了强光下不同供氮水平（12、4和0.4 mmol·L^-1）和不同CO₂浓度下（700和390 μl·L^-1）丰香草莓叶片的荧光参数及净光合速率的变化.结果表明,CO₂和氮素对草莓叶片光抑制有明显的互作效应.在富CO₂下,12 mmol·L^-1供氮水平的草莓叶片净光合速率升高了62.7%,4和0.4 mmol·L^-1供氮水平则分别降低了7.4%和21.3%;12 mmol·L^-1供氮水平的F_m和F_v/F_m在强光胁迫时降辐减小,暗恢复时F_m和F_v/F_m恢复程度提高,而4和0.4 mmol·L^-1供氮水平却相反.表明氮素供应不足时草莓叶片在富CO₂环境下光合作用出现适应性下调,光抑制增强.     

水稻寡分蘖突变体的遗传分析和基因定位

从籼粳交组合“圭630/02428”的花培后代中获得一份寡分蘖突变体G069,其主要特征是分蘖速度慢,最高分蘖数少,成熟叶片叶尖、叶缘黄化.用突变体作母本与02428杂交,并以02428作轮回亲本与杂交后代突变型单株回交构建BC₂F₂.对BC₂F₂进行调查和遗传分析,确认突变体G069寡分蘖特性和叶片黄化现象受同一隐性基因控制.以BC₂F₂分离群体为基础,应用SSR标记和RFLP标记进行连锁分析,将寡分蘖基因定位于第2染色体的RFLP标记C424和S13984之间,分别相距2.4和0.6cM.该基因暂定名为ft1.     

处理对菊芋幼苗光合及叶绿素荧光的影响

以砂培菊芋(Helianthus tuberosus)幼苗作为试验材料,分别进行不同浓度NaCl (50、 100、150、200、250 mmol•L^－1)和Na₂CO₃ (25、50、 75、100、125 mmol•L^－1)胁迫处理,以1/2全营养液作为对照,处理7 d后研究NaCl和Na₂CO₃胁迫处理对菊芋幼苗叶片光合作用及叶绿素动力学 参数的影响。结果表明：1)在NaCl处理下,当浓度小于150 mmol•L^－1时,增加了菊芋的叶绿素含量、净光合速率(Net photosynthetic rate, P_n)和气孔导度(Stomatal conductivity, G_s),对荧光参数PSⅡ的电子传递情况( F_m/F_o)、PSⅡ原初光能转换效率(F_v/F_m)、PSⅡ量子效率 (Actual quantum yield of PSⅡ under actinic irradiation,φPSⅡ)和光化学猝灭系数(Photochemical quenching coefficient, qP)和非 光化学猝灭系 数(Non-photochemical quenching coefficient, NPQ)没有显著影响,随着浓度的增加,各项生理指标与对照相比除了NPQ显著 增加,其余均显著降低;2)在Na₂CO₃胁迫处理下,随着Na₂CO₃浓度的增加,与对照相比菊芋幼苗叶绿素含量、P_n、G_s以及叶绿素a荧光诱导动力 学参数F_m/F_o、F_v/F_m、φPSⅡ和qP均显著降低,NPQ显著增加;3)就NaCl和Na₂CO₃相比而言,在相同Na⁺浓度情况下,处于Na₂CO₃胁迫下的菊芋 幼苗的叶绿素含量、P_n、G_s以及叶绿素a荧光诱导动力学参数F_m/F_o、F_v/F_m、φPSⅡ和qP下降幅度和NPQ的增加幅度均显著大于NaCl,这说明 NaCl和Na₂CO₃胁迫均对菊芋幼苗造成不同程度的伤害,但在相同Na⁺浓度情况下,Na₂CO₃的伤害程度大于NaCl。由此说明菊芋对盐的忍耐程度高 于碱。     

利用四价抗病基因提高超级杂交稻的抗性

以籼型超级杂交稻(Oryza sativa L. subsp. indica)恢复系9311的胚性愈伤组织为受体, 采用改良的基因枪轰击法将构建在同一植物表达载体上的四价抗真菌病基因(RCH10, RAC22, β-Glu和B-RIP)导入到9311的基因组中. Southern印迹杂交结果表明, 潮霉素抗性再生植株中, hpt标记基因和四价抗真菌病基因是连锁在一起并以孟德尔遗传方式进行传递的. 部分转基因R₁代和R₂代植株分别在烟溪和三亚的典型稻瘟病鉴定圃中表现出对稻瘟病菌(Magnaporthe grisea (Hebert) Barr.)的高抗性. 在高抗的转基因植株中, 多个外源基因均能正常表达. 将高抗稻瘟病的9311 R2代转基因纯系与培矮64S原种进行杂交, 杂种F₁代除对稻瘟病仍可表现出高抗性外, 还同时表现出对稻曲病和黑粉病明显提高的抗性.     

Islet1基因与心脏发育

心脏发育及心脏疾病干细胞的治疗要求对心脏发育过程中的控制细胞增殖及分化的相关基因的作用机制进行深入了解.Islet1基因(Isl1基因)含有6个外显子和5个内含子,定位于人类5号染色体5q11.2.该基因在基因组内约占12kb,目前所知其最长可读框(ORF)至少由5个外显子组成,编码一个由384个氨基酸组成的转录因子蛋白.最近研究发现,不同的心脏细胞可能源于同一种多能心脏祖细胞—Isl1+细胞,心脏的这一发育模式与血液细胞的形成模式非常相像.另外有研究结果显示,Isl1是与心脏发育密切相关的转录因子之一,其表达随着心脏发育成熟而逐渐下调.虽然针对Isl1基因做了较多的研究工作,但是它表达调控的具体模式及发挥功能的详细作用机制目前仍未完全清楚,本文对最近几年Isl1基因的研究进展作一综述.     

Changes in ion fluxes during phototropic bending of etiolated oat coleoptiles

BACKGROUND AND AIMS: This work has been conducted to assist theoretical modelling of the different stages of the blue light (BL)-induced phototropic signalling pathway and ion transport activity across plant membranes. Ion fluxes (Ca(2+), H(+), K(+) and Cl(-)) in etiolated oat coleoptiles have been measured continuously before and during unilateral BL exposure. METHODS: Changes in ion fluxes at the illuminated (light) and shadowed (dark) sides of etiolated oat coleoptiles (Avena sativa) were studied using a non-invasive ion-selective microelectrode technique (MIFE). The bending response was also measured continuously, and correlations between the changes in various ion fluxes and bending response have been investigated. For each ion the difference (Delta) between the magnitudes of flux at the light and dark sides of the coleoptile was calculated. KEY RESULTS: Plants that demonstrated a phototropic bending response also demonstrated Ca(2+) influx into the light side approximately 20 min after the start of BL exposure. This is regarded as part of the perception and transduction stages of the BL-induced signal cascade. The first 10 min of bending were associated with substantial influx of H(+), K(+) and Cl(-) into the light (concave) side of the coleoptiles. CONCLUSIONS: The data suggest that Ca(2+) participates in the signalling stage of the BL-induced phototropism, whereas the phototropic bending response is linked to changes in the transport of H(+), K(+) and Cl(-).     

Calcium in plants

Calcium is an essential plant nutrient. It is required for various structural roles in the cell wall and membranes, it is a counter-cation for inorganic and organic anions in the vacuole, and the cytosolic Ca2+ concentration ([Ca2+]cyt) is an obligate intracellular messenger coordinating responses to numerous developmental cues and environmental challenges. This article provides an overview of the nutritional requirements of different plants for Ca, and how this impacts on natural flora and the Ca content of crops. It also reviews recent work on (a) the mechanisms of Ca2+ transport across cellular membranes, (b) understanding the origins and specificity of [Ca2+]cyt signals and (c) characterizing the cellular [Ca2+]cyt-sensors (such as calmodulin, calcineurin B-like proteins and calcium-dependent protein kinases) that allow plant cells to respond appropriately to [Ca2+]cyt signals.     

蜂毒肽的溶血作用与红细胞膜上两种酶活性变化的关系

从蜂毒肽作用于红细胞膜上的Na^＋-K^＋-ATPase和葡萄糖-6-磷酸脱氢酶(G-6-PD)活性变化的角度,利用分光光度法测定酶活性,研究蜂毒肽与红细胞及膜作用过程中可能的靶点,讨论了蜂毒肽溶血过程与RBC膜上2种酶活性的变化．结果发现,蜂毒肽抑制RBC膜上酶活性的主要模式为附着/插入质膜与游离态并存模式,附着/插入质膜中的作用大于游离态的作用．Na^＋-K^＋-ATPase的K⁺结合位点是蜂毒肽的1个作用靶点．蜂毒肽插膜过程与其对此酶的作用随时间延长同步发生．蜂毒肽通过作用于葡萄糖-6-磷酸和NADP使G-6-PD的催化受到缓慢抑制,蜂毒肽形成四聚体的程度与酶活性密切相关．EDTA抑制蜂毒肽聚集,干扰蜂毒肽作用于G-6-P,蜂毒肽作用于底物G-6-P及辅酶NADP的生化机理相似,蜂毒肽抑制作用与G-6-PD的结构无关.     

高温胁迫对花生幼苗光合速率、叶绿素含量、叶绿体Ca2+-ATPase、Mg2+-ATPase及Ca2+分布的影响

将水培后盆栽的花生幼苗,置于培养箱42℃高温培养,定时测定幼苗叶光合速率、叶绿素含量和叶绿体Ca²⁺-ATPase、Mg²⁺-ATPase的相对活性,并观察幼叶细胞内Ca²⁺分布的变化。试验结果表明：高温胁迫过程中,光合速率及叶绿素含量都随处理时间的延伸而下降,并呈显著正相关;叶绿体Ca²⁺-ATPase和Mg²⁺-ATPase高温胁迫过程中相对活性呈先升后降趋势,Ca²⁺-ATPase热敏性高于Mg²⁺-ATPase;高温胁迫过程中,Ca²⁺具有从胞外转运到胞质内和叶绿体中的趋势,Ca²⁺能够稳定高温胁迫下叶肉细胞膜和叶绿体的超微结构。     

Leaf water relations and net gas exchange responses of salinized Carrizo citrange seedlings during drought stress and recovery

BACKGROUND AND AIMS: Since salinity and drought stress can occur together, an assessment was made of their interacting effects on leaf water relations, osmotic adjustment and net gas exchange in seedlings of the relatively chloride-sensitive Carrizo citrange, Citrus sinensis x Poncirus trifoliata. METHODS: Plants were fertilized with nutrient solution with or without additional 100 mm NaCl (salt and no-salt treatments). After 7 d, half of the plants were drought stressed by withholding irrigation water for 10 d. Thus, there were four treatments: salinized and non-salinized plants under drought-stress or well-watered conditions. After the drought period, plants from all stressed treatments were re-watered with nutrient solution without salt for 8 d to study recovery. Leaf water relations, gas exchange parameters, chlorophyll fluorescence, proline, quaternary ammonium compounds and leaf and root concentrations of Cl(-) and Na(+) were measured. KEY RESULTS: Salinity increased leaf Cl(-) and Na(+) concentrations and decreased osmotic potential (Psi(pi)) such that leaf relative water content (RWC) was maintained during drought stress. However, in non-salinized drought-stressed plants, osmotic adjustment did not occur and RWC decreased. The salinity-induced osmotic adjustment was not related to any accumulation of proline, quaternary ammonium compounds or soluble sugars. Net CO(2) assimilation rate (A(CO2)) was reduced in leaves from all stressed treatments but the mechanisms were different. In non-salinized drought-stressed plants, lower A(CO2) was related to low RWC, whereas in salinized plants decreased A(CO2) was related to high levels of leaf Cl(-) and Na(+). A(CO2) recovered after irrigation in all the treatments except in previously salinized drought-stressed leaves which had lower RWC and less chlorophyll but maintained high levels of Cl(-), Na(+) and quaternary ammonium compounds after recovery. High leaf levels of Cl(-) and Na(+) after recovery apparently came from the roots. CONCLUSIONS: Plants preconditioned by salinity stress maintained a better leaf water status during drought stress due to osmotic adjustment and the accumulation of Cl(-) and Na(+). However, high levels of salt ions impeded recovery of leaf water status and photosynthesis after re-irrigation with non-saline water.     

向日葵(Helianthus annuus L.)对133Cs、88Sr的吸收和分布

通过盆栽试验研究了向日葵(Helianthus annuus L.)对土壤中不同处理浓度¹³³Cs和⁸⁸Sr的吸收,以及¹³³Cs和⁸⁸Sr在向日葵不同部位的分布。结果表明：随着处理浓度的增加,植物中¹³³Cs或⁸⁸Sr的含量增加。同一处理浓度下,⁸⁸Sr含量约比¹³³Cs含量高一个数量级。¹³³Cs和⁸⁸Sr在植物不同部位分布不同。根部中¹³³Cs含量高于植物的其他部位（茎、叶、花）。不同于¹³³Cs在植物中的分布,⁸⁸Sr除在根中的分布外,主要转运到了叶片。¹³³Cs和⁸⁸Sr在向日葵体内的分布与目前对放射性¹³⁷Cs和⁹⁰Sr的研究结果相似,所以¹³³Cs和⁸⁸Sr可分别预测¹³⁷Cs和⁹⁰Sr的运转。向日葵是治理大面积低放核素污染土壤的较佳植物种类。     

Periplasm turgor pressure controls wall deposition and assembly in growing Chara corallina cells

BACKGROUND AND AIMS: New wall deposition usually accompanies plant growth. External osmotica inhibit both processes but wall precursors continue to be synthesized, and exocytosis follows. Consequently, the osmotica appear to act outside of the plasma membrane. Because this implies an action of turgor pressure (P) on the periplasm by unknown mechanisms, the following study was undertaken to determine whether P could act in a way that altered wall deposition and assembly in the periplasm while the cells grow. METHODS: Cells of Chara corallina were exposed to P slightly below normal by using a pressure probe while supplying inorganic carbon in light. After labelling, the walls were isolated and the amount of new wall was determined. Similar measurements were made after treatment with osmotica. Chlortetracycline-stimulated exocytosis was determined microscopically. Polysaccharide properties were determined by confocal microscopy and vapour pressure osmometry in an 'artificial periplasm' in isolated Chara cell walls, using labelled dextran as an analogue of hemicellulose, and polygalacturonate as pectin. KEY RESULTS: Rapid growth and wall deposition occurred at normal P of 0.5 MPa but both processes decreased when P was lowered 0.1 MPa. Inorganic carbon uptake and exocytosis were unaffected. In the artificial periplasm, normal P caused high polysaccharide concentrations and rapid polysaccharide entry into the wall, and gel formation in the pectin. Lowering P decreased entry and gel formation. CONCLUSIONS: This is the first indication that normal P of 0.5 MPa can concentrate periplasmic polysaccharides sufficiently to cause cross-linking and gel formation in pectins while simultaneously fostering the entry of large polysaccharides into small interstices in the existing wall. This P-action would thicken the primary wall and form a smooth transition between the new and old structure, suggesting a molecular mechanism of wall deposition and assembly while the wall extends.     

Incorporation of orally applied (13)C-galactose into milk lactose and oligosaccharides

Biosynthesis and functions of human milk oligosaccharides (HMO) are not well known. A typical housekeeping enzyme, beta1,4-galactosyltransferase, links galactose to glucose to form lactose which is then used as backbone for the assembly of HMO. We investigated whether milk lactose and HMO may be labeled in vivo by an orally given (13)C-galactose bolus. Eleven exclusively breastfeeding mothers were given a (13)C-galactose bolus at the end of their breakfast. Milk and urine samples from each nursing up to 36 h were analyzed for carbohydrate composition by high-performance thin-layer chromatography, high-pH anion-exchange chromatography, and fast atom bombardment mass spectrometry. (13)C enrichment of milk fractions, urinary carbohydrates, lactose, and oligosaccharides as well as of breath CO(2) was determined by isotope ratio mass spectrometry. Up to 10% of the orally given galactose bolus was directly transported to the mammary gland and incorporated into milk components. Characteristic for most milk samples was the appearance of two (13)C-peaks, the first immediately after the (13)C-bolus was taken and the second on the next morning. The highest (13)C enrichment was found in lactose followed by neutral and acidic oligosaccharides. In breath samples, the (13)C-excretion followed the same pattern as in milk. (13)C nuclear magnetic resonance of isolated lactose revealed (13)C only at C(1)-atom of galactose and C(1)-atom of glucose. This label was without any exception at the same position as the (13)C-label of the orally applied galactose. Neutral and acidic HMO can easily be (13)C-labeled in vivo which facilitates investigations of their metabolic fate in infants.     

Evidence of phloem boron transport in response to interrupted boron supply in white lupin (Lupinus albus L. cv. Kiev Mutant) at the reproductive stage

The present study investigates whether previously acquired boron(B) in mature leaves in white lupin can be retranslocated intothe rapidly growing young reproductive organs, in response toshort-term (3 d) interrupted B supply. In a preliminary experimentwith white lupin in soil culture, B concentrations in phloemexudates remained at 300–500 µM, which were substantiallyhigher than those in the xylem sap (10–30 µM). Thehigh ratios of B concentrations in phloem exudates to thosein the xylem sap were close to values published for potassiumin lupin plants. To differentiate ‘old’ B in theshoot from ‘new’ B in the root, an experiment wascarried out in which the plants were first supplied with 20µM ¹¹B (99.34% by weight) in nutrient solution for 48d after germination (DAG) until early flowering and then transferredinto either 0.2 µM or 20 µM ¹⁰B (99.47% by weight)for 3 d. Regardless of the ¹⁰B treatments, significant levelsof ¹¹B were found in the phloem exudates (200–300 µMin 20 µM ¹⁰B and 430 µM in 0.2 µM ¹⁰B treatment)and xylem sap over the three days even without ¹¹B supply tothe root. In response to the 0.2 µM ¹⁰B treatment, thetranslocation of previously acquired ¹¹B in the young (the uppermostthree leaves), matured, and old leaves was enhanced, coincidingwith the rise of ¹¹B in the xylem sap (to >15 µM) andphloem exudates (430 µM). The evidence supports the hypothesisthat previously acquired B in the shoot was recirculated tothe root via the phloem, transferred into the xylem in the root,and transported in the xylem to the shoot. In addition, somepreviously acquired ¹¹B in the leaves may have been translocatedinto the rapidly growing inflorescence. Phloem B transport resultedin the continued net increment of ¹¹B in the flowers over 3d without ¹¹B supply. However, it is still uncertain whetherthe amount of B available for recirculation is adequate to supportreproductive growth until seed maturation. Key words: ¹⁰B, ¹¹B, B recirculation, Lupinus albus L., phloem exudate, xylem sap Received 9 October 2007; Revised 28 November 2007 Accepted 30 November 2007