光呼吸突变体研究进展

光呼吸(photorespiration)是绿色植物在光下吸收氧气并释放CO₂的过程。C₃植物光呼吸可消耗25%光合产物, 故合理改良光呼吸可望提高植物的光合效率。筛选与利用光呼吸突变体是研究光呼吸代谢及其功能的最为有效的途径。该文对光呼吸代谢途径、光呼吸突变体的筛选以及研究进展进行综述, 以期为深入探讨植物光呼吸的生物学功能及进行植物分子改良提供帮助。     

光呼吸突变体研究进展

光呼吸（photorespiration）是绿色植物在光下吸收氧气并释放CO2的过程。C3植物光呼吸可消耗25%光合产物,故合理改良光呼吸可望提高植物的光合效率。筛选与利用光呼吸突变体是研究光呼吸代谢及其功能的最为有效的途径。该文对光呼吸代谢途径、光呼吸突变体的筛选以及研究进展进行综述,以期为深入探讨植物光呼吸的生物学功能及进行植物分子改良提供帮助。     

C4植物的光呼吸

自50年代 Decker 发现光呼吸后的一段时间里,有些学者认为 C_4植物是非光呼吸型的。70年代以后,越来越多的人证明 C_4植物是有光呼吸的。本文报道我们近年来对 C_4植物光呼吸测定的结果。     

光呼吸条件下栾树和辣椒光合电子流的分配研究

用Li-6400光合仪同时测定了栾树和辣椒在温度为30℃、CO2浓度为380μmol·mol-1下的气体交换和叶绿素荧光数据。结果表明,栾树在饱和光合有效辐射时光合电子用于碳同化、光呼吸和其他途径的量分别为72.68、45.68和29.40μmol·m-2.s-1;辣椒在光合有效辐射为2000μmol·m-2.s-1时光合电子用于碳同化、光呼吸和其他途径的量分别为142.24、40.24和131.52μmol·m-2.s-1。揭示了在光呼吸条件下用Valentini和Epron等方法高估了辣椒和栾树的光合电子用于光呼吸的量,同时也高估了光呼吸在辣椒和栾树中的保护作用。     

光呼吸途径及其功能

光呼吸是C3植物体内重要的代谢过程,是光合作用研究的热点之一。本文阐述了光呼吸的正常代谢途径及乙醛酸代谢的交替途径,交替途径的功能,及途径中关键酶的生物 学特性。就光呼吸在减轻逆境伤害、减缓叶绿素的降解、驱动卡尔文循环、参与三羧酸循环、氮素代谢、蛋白质积累以及PSⅠ和PSⅡ之间的状态转换等生物学功能进行了综述。     

光呼吸途径及其功能

光呼吸是C3植物体内重要的代谢过程,是光合作用研究的热点之一。本文阐述了光呼吸的正常代谢途径及乙醛酸代谢的交替途径,交替途径的功能,及途径中关键酶的生物学特性。就光呼吸在减轻逆境伤害、减缓叶绿素的降解、驱动卡尔文循环、参与三羧酸循环、氮素代谢、蛋白质积累以及PSI和PSⅡ之间的状态转换等生物学功能进行了综述。     

关于光呼吸的化学控制的研究

水稻、小麦施用光呼吸抑制剂NaHSO_3经三年研究结果证明,在100～300 ppm范围内能使净光合率提高4～18％,通过低氧(2％)与光强的验证指出,净光合提高主要系光呼吸被抑制的结果,一般光呼吸抑制率在20％左右,而且光呼吸抑制与乙醇酸含量的增加等有关参数均表现一致。 NaHSO_3对光呼吸及光合作用似都有影响,不过对光呼吸抑制率远大于对光合作用不利效应,故净光合率仍表现提高。 采用~(35)S标记NaHSO_3叶面喷施证明,稻、麦对外用抑制剂能很快地吸收,这为抑制剂的田间施用提供了可能。     

C3植物过氧物酶体酶活性的比较

菠菜等9种C_3植物过氧物酶体中与光呼吸有关的酶活性的差异,不足以说明不同 C_3植物的光呼吸明显差异,它可能是参与光呼吸的酶组成不同效率的多酶体系所致,或者是由过氧物酶体以外的原因所引起。     

C_3-C_4中间植物

C_3—C_4中间植物是在解剖和生理生化方面(特别是光呼吸)介于C_3和C_4植物之间的一种植物类型。这类植物中一部分接近C_3植物,可将光呼吸放出的CO_2再固定,从而降低光呼吸;另一些则以C_3途径为主,而C_4途径同时起作用,从而降低光呼吸。C_3—C_4中间植物为研究C_4植物的进化和光呼吸如何降低提供了实验系统。     

光呼吸研究进展

光呼吸是指植物绿色组织依赖光能吸收O₂并释放CO₂的过程,它被认为是一个浪费能量的过程。正常生长的C₃植物光呼吸可损耗光合产物的25%~30%,在干旱、高温、高光等逆境胁迫下,该损耗可高达50%,因此,显著提高C₃植物的生产力可通过减少光呼吸通量来实现。尽管光呼吸对植物生产力的负面影响明显,但它对植物一些必要生理活动可能起着重要作用,其中包括参与光保护、H₂O₂信号发生、氮代谢、光氧化和抗逆反应等。该文对光呼吸的改造优化需要把握好平衡点与适配度。基于Rubisco改造、CO₂浓缩机制(CCM)和光呼吸支路创建的光呼吸改造研究进展进行了综述。通过了解调控光呼吸提高植物光能转化效率方面的最新进展, 可望为光呼吸代谢的分子调控及改良研究提供指导。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.