Variation of the Cytoplasm Type in Sugar Beet (Beta vulgaris L.) upon Inbreeding: Influence of Hybridization

Hybrid combinations of inbred sugar beet lines that undergo conversion of N-cytoplasm into S-state were screened for the marker mitochondrial genes atpA and atp6. The involvement of nuclear factors into cytoplasm conversion and possible identity of these factors in different lines have been studied. The cytoplasm conversion factor was localized to nucleus. In different lines with cytoplasm conversion, the nuclear conversion factors are not identical. The state of the mitochondrial genome is normalized after outcrosses with plants having the stable cytoplasm.     

Quantitative variation in components of the maize mitochondrial genome between tissues and between plants with different male-sterile cytoplasms

Summary The amounts of a 1.9 kb mitochondrial plasmid relative to sequences in another mitochondrial DNA replicon and also to nuclear ribosomal DNA sequences have been compared in maize leaves and anthers. Similar comparisons have been made between plants with the same nuclear genotype but containing normal, S, or T cytoplasms. The ratio of 1.9 kb plasmid to nuclear rDNA is lower in plants with normal cytoplasm than in plants with S or T cytoplasm. It also differs between leaves and anthers. Furthermore, the relative concentration of the mitochondrial DNA sequences belonging to different replicons differs between leaves and anthers. It is concluded that components of different mitochondrial replicons are not maintained in fixed ratios during development and that the concentration of the 1.9 kb plasmid is regulated, in part, by cytoplasmically-inherited determinants. The 1.9 kb plasmid is absent from lines with the Vg cytoplasm, but related sequences are found in the maize nuclear genome.     

Classification of Normal and Male-Sterile Cytoplasms in Maize. II. Electrophoretic Analysis of DNA Species in Mitochondria

Mitochondrial DNA preparations were made from 31 maize lines carrying different sources of cytoplasm in the same nuclear genetic background. The DNAs were analyzed by agarose gel electrophoresis. A number of discrete low molecular weight bands were present in all lines. However, only four different DNA banding patterns were observed. These were correlated with the N, T, S and C cytoplasms defined by nuclear fertility restorer genes. Of the 31 cytoplasmic sources examined, six possessed DNA species characteristic of N cytoplasms, four possessed DNA species characteristic of T cytoplasm, 19 possessed DNA species characteristic of S cytoplasm and two possessed DNA species characteristic of C cytoplasm. This classification is in complete agreement with that based on mitochondrial translation products reported in the accompanying paper. No within-group heterogeneity was observed in the DNA banding patterns, indicating a lack of cytoplasmic variation within the four cytoplasmic groups. Attributes of the various methods available for classifying maize cytoplasms are compared and discussed.     

玉米S组细胞质雄性不育线粒体R区序列与多型性分析

玉米Ｓ组细胞难性不育（ＣＭＳ）可能与线粒体基因组中的Ｒ区域有关。对不同核背景下唐徐、双２种Ｓ胞质的线粒体ＤＮＡ以Ｒ区特异探针的Ｓｏｕｔｈｅｒｎ分析发现均有６．７ｋｂ、４．５ｋｂ、１．８ｋｂ的３条谱带,分别对应于２种位于线粒体基因组中间的类型和１个线性末端,并且核背景对这３种不同形式的Ｒ区域的量有影响。对Ｍｏ１７和７７核背景下Ｎ、Ｔ、Ｃ４种胞质１７种材料的玉米线粒体基因组中Ｒ区的Ｓｏｕｔｈｅｒｎ分析     

RAPD Comparison Study on Mitochondrial DNA of the D2 Cytoplasmic Male Sterile (CMS) Line with K-, V-and T-type CMS Lines in Wheat

A new line of cytoplasmic male sterile (CMS) wheat ( Triticum aestivum L. ) named msD2-CA8057 (briefly as D:) was compared with K-, V- and T-type CMS lines by mitochondrial DNA (mtDNA) RAPD analysis. It was revealed that the mtDNA of this D2 line was different from that of the other three types although differences were also found between the K-, V- and T-type lines themselves. This result provided some evidences at the molecular level for the identification of the cytoplasm of this D2 line as a new type of CMS line. In the experiment the authors also found polymorphism between two CMS lines, which had the same source of T-type cytoplasm but had different nuclear background. This was the first time to provide direct evidence about the mtDNA mutation in T-type CMS wheat lines during the routine backcross process. Such changes are most likely resulted from the influence of different nuclear background.     

Characterization of the Host Factors Required for Hepadnavirus Covalently Closed Circular (ccc) DNA Formation

Synthesis of the covalently closed circular (ccc) DNA is a critical, but not well-understood step in the life cycle of hepadnaviruses. Our previous studies favor a model that removal of genome-linked viral DNA polymerase occurs in the cytoplasm and the resulting deproteinized relaxed circular DNA (DP-rcDNA) is subsequently transported into the nucleus and converted into cccDNA. In support of this model, our current study showed that deproteinization of viral double-stranded linear (dsl) DNA also took place in the cytoplasm. Furthermore, we demonstrated that Ku80, a component of non-homologous end joining DNA repair pathway, was essential for synthesis of cccDNA from dslDNA, but not rcDNA. In an attempt to identify additional host factors regulating cccDNA biosynthesis, we found that the DP-rcDNA was produced in all tested cell lines that supported DHBV DNA replication, but cccDNA was only synthesized in the cell lines that accumulated high levels of DP-rcDNA, except for NCI-H322M and MDBK cells, which failed to synthesize cccDNA despite of the existence of nuclear DP-rcDNA. The results thus imply that while removal of the genome-linked viral DNA polymerase is most likely catalyzed by viral or ubiquitous host function(s), nuclear factors required for the conversion of DP-rcDNA into cccDNA and/or its maintenance are deficient in the above two cell lines, which could be useful tools for identification of the elusive host factors essential for cccDNA biosynthesis or maintenance.     

小麦D^2型与K型,V型,T型细胞质雄性不育系线粒体DNA的RAPD比较分析

采用ＲＡＰＤ方法比较新育成的小麦（ＴｒｉｔｉｃｕｍａｅｓｔｉｖｕｍＬ．）Ｄ２型不育系ｍｓＤ２ＣＡ８０５７与Ｋ型、Ｖ型和Ｔ型细胞质雄性不育系的线粒体ＤＮＡ（ｍｔＤＮＡ）。结果表明,ｍｓＤ２ＣＡ８０５７的ｍｔＤＮＡ不同于其它３种类型不育系,而其它类型不育系的ｍｔＤＮＡ彼此也各不相同。这一结果从分子水平上为鉴定该Ｄ２不育系的不育类型提供了证据。实验还发现在胞质来源相同而核背景不同的Ｔ型不育系间存在线粒体基因组多态性,这是关于小麦中Ｔ型不育系ｍｔＤＮＡ在常规回交转育过程中发生变异的直接证据。这种变异在很大程度上可能是受不同核背景影响的结果。     

Caspase-2 can trigger cytochrome C release and apoptosis from the nucleus

The cysteine proteases specific for aspartic residues, known as caspases, are localized in different subcellular compartments and play specific roles during the regulative and the executive phase of the cell death process. Here we investigated the subcellular localization of caspase-2 in healthy cells and during the execution of the apoptotic program. We have found that caspase-2 is a nuclear resident protein and that its import into the nucleus is regulated by two different nuclear localization signals. We have shown that in an early phase of apoptosis caspase-2 can trigger mitochondrial dysfunction from the nucleus without relocalizing into the cytoplasm. Release of cytochrome c occurs in the absence of overt alteration of the nuclear pores and changes of the nuclear/cytoplasmic barrier. Addition of leptomycin B, an inhibitor of nuclear export, did not interfere with the ability of caspase-2 to trigger cytochrome c release. Only during the late phase of the apoptotic process can caspase-2 relocalize in the cytoplasm, as consequence of an increase in the diffusion limits of the nuclear pores. Taken together these data indicate the existence of a nuclear/mitochondrial apoptotic pathway elicited by caspase-2.     

粗厚山羊草（Ae.crassa）细胞质普通小麦核代换系在中国不同光温条件地点的雄性育性变异

5个普通小麦品系的粗厚山羊草4X,6X种细胞质的7个核代换系在中国昆明,元谋,杨陵,互助,依安5个不同纬度地点种植的自交结实率,结合各点光温条件的分析表明,粗厚山羊草细胞质普通小麦核代换系的雄性育性随日长增加而下降,6X种细胞质核代换系在日长≥14.28h开始出现完全雄性不育,4X种细胞质核代换系在日长≥15.38h开始出现完全雄性不育;该细胞质核代换系的雄性育性在日长因子主控下,对温度变化也表现一定敏感性。粗厚山羊草细胞质背景下不同核基因型对光,温条件的敏感性有显著差异。核质互作效应是这种敏感性的遗传方式,粗厚山羊草4X、6X种细胞质的光,温敏感性存在差异。6X种细胞质的光,温敏感性高于4X种细胞质。     

Small mitochondrial DNA molecules of wild abortive cytoplasm in rice are not necessarily associated with CMS

Summary Mitochondrial DNA was isolated from leaf tissue of both the cytoplasmic male sterile line of Indica rice variety V41, which carries wild abortive (WA) cytoplasm, and from the corresponding maintainer line. In addition to the main mitochondrial DNA, four small plasmid-like DNA molecules were detected in both the male sterile and fertile lines. Restriction analysis of total mitochondrial DNA from the male sterile and fertile lines showed DNA fragments unique to each. Our findings suggest that the four small mitochondrial DNA (mtDNA) molecules are conserved when WA cytoplasm is transferred into different nuclear backgrounds. However, there is no simple correlation between the presence/ absence of small mitochondrial DNA molecules and the expression of WA cytoplasmic male sterility (CMS).     

Identification of Cytoplasmic Male Sterility in Chinese Radish Following PCR Analysis of Mitochondrial DNA

In order to understand the molecular characteristics of the Chinese radish, the mitochondrial DNA structure and sequence were analyzed in Chinese wild radish and cultivated varieties. A total of four male-sterile lines, four maintainer lines, 17 cultivars, and a single Chinese wild radish were used, along with 25 male-sterile individuals and 159 fertile plants. We found that the cytoplasm of Chinese radishes could be classified into two types: the normal type and the Ogura type. The Ogura-type cytoplasm was detected in 25 male-sterile plants. The 159 fertile plants had normal cytoplasm. Both the Ogura cytoplasm and the normal cytoplasm were detected in the male-sterile ??RA??. The orf138 gene in mitochondrial DNA was detected in cultivated Chinese radish cultivars but not in the wild radish. The Chinese radish orf138 nucleotide sequence was determined in four male-sterile lines and displayed complete homology to the known orf138 type A nucleotide sequence. Three types of mitochondrial orfB (type 1, type 2 and type 3) were found in Chinese radishes. Type 1 was only present in the male-sterile lines. Chinese cultivated radishes were divided into type 2 and type 3, while the Chinese wild radish only had type 3 cytoplasm.     

Mitochondrial aldehyde dehydrogenase activity is required for male fertility in maize

Some plant cytoplasms express novel mitochondrial genes that cause male sterility. Nuclear genes that disrupt the accumulation of the corresponding mitochondrial gene products can restore fertility to such plants. The Texas (T) cytoplasm mitochondrial genome of maize expresses a novel protein, URF13, which is necessary for T cytoplasm-induced male sterility. Working in concert, functional alleles of two nuclear genes, rf1 and rf2, can restore fertility to T cytoplasm plants. Rf1 alleles, but not Rf2 alleles, reduce the accumulation of URF13. Hence, Rf2 differs from typical nuclear restorers in that it does not alter the accumulation of the mitochondrial protein necessary for T cytoplasm-induced male sterility. This study established that the rf2 gene encodes a soluble protein that accumulates in the mitochondrial matrix. Three independent lines of evidence establish that the RF2 protein is an aldehyde dehydrogenase (ALDH). The finding that T cytoplasm plants that are homozygous for the rf2-R213 allele are male sterile but accumulate normal amounts of RF2 protein that lacks normal mitochondrial (mt) ALDH activity provides strong evidence that rf2-encoded mtALDH activity is required to restore male fertility to T cytoplasm maize. Detailed genetic analyses have established that the rf2 gene also is required for anther development in normal cytoplasm maize. Hence, it appears that the rf2 gene was recruited recently to function as a nuclear restorer. ALDHs typically have very broad substrate specificities. Indeed, the RF2 protein is capable of oxidizing at least three aldehydes. Hence, the specific metabolic pathway(s) within which the rf2-encoded mtALDH acts remains to be discovered.     

The PKC delta inhibitor, rottlerin, induces apoptosis of haematopoietic cell lines through mitochondrial membrane depolarization and caspases' cascade

Rottlerin is a widely selective protein kinase C delta (PKCdelta) inhibitor isolated from Mallotus philippinensis. It shown to be effective against several human tumor cell lines and in potentiating chemotherapy-induced cytotoxcicity. Using the trypan blue exclusion assay, we demonstrated that rottlerin reduced the viability in a dose- and time-dependent manner of human leukemia HL60 cells, human acute T cell leukemia Jurkat cells and mouse macrophage RAW 264.7 cells. Rottlerin caused apoptosis and the apaptotic processing was inhibited by a caspase inhibitor, z-VAD-fmk, in these haematopoietic cells. The apoptosis-inducing activities were determined by nuclear condensation, sub-G1 appearance, DNA fragmentation, loss of mitochondrial membrane potential (Deltapsim), release of mitochondrial cytochrome c into cytoplasm and proteolytic activation of caspase 9 and 3. Expression of PKCdelta and Bcl-2 protein inhibited Deltapsim change and repressed cell death. These studies suggest that the cytotoxic effects of rottlerin through inhibition of PKCdelta cause mitochondrial dysfunction, cytochrome c release from mitochondria into cytoplasm and the activation of caspases' cascade.     

Molecular analysis of mitochondria from a fertility restorer line of maize

Summary Inbred line Ky21 carries nuclear genes which restore fertility to all three cytoplasmic male sterile (cms) types of maize: T, C and S. By substituting the Ky21 cytoplasm into a nuclear background lacking all of the nuclear restorer genes, we have demonstrated that Ky21 contains a fertile (normal) cytoplasm. Gel electrophoresis of mitochondrial DNA from Ky21 demonstrated an approximately 2.1 kb plasmid and no evidence for a 2.35 kb plasmid found in many normal cytoplasms of North American lines of maize. A 2.1 kb plasmid had been reported to be diagnostic for the T-type cms. However, the restriction endonuclease digestion pattern of Ky21 mtDNA more closely resembled that of normal lines than T-cms. Furthermore, mitochondria of Ky21 plants did not synthesize a 13 kilodalton polypeptide, which has only been found to be synthesized by T-type mitochondria. From these molecular criteria, as well as from the genetic analysis, we conclude that the mitochondria of the Ky21 universal restorer line are normal. In having a shorter form of a linear mtDNA plasmid, Ky21 resembles cytoplasms found in Mexican races of maize.