Double-stranded RNA replicons associated with chloroplasts of a green alga,Bryopsis cinicola

Double-stranded RNAs (dsRNAs) associated with chloroplasts and mitochondria have been found in the coenocytic green alga Bryopsis cinicola. In this study we report molecular properties of the four chloroplast-associated dsRNAs (BDRC1 to BDRC4) The longest dsRNA molecule (BDRC1) was sequenced entirely (1959 bp) and a single large ORF of 1722 bp was found within it. Database searches revealed similarities between the deduced amino acid sequence of this ORF and RNA-dependent RNA polymerase (RdRp) sequences from several RNA viruses. The most similar sequence in the database was the RdRp of beet cryptic virus 3. Phylogenetic analysis revealed that the RdRp-like sequence of BDRC1 can be placed in the Partitiviridae clade. To detect autonomous replication of these dsRNAs, RdRp assays were carried out with actinomycin D, which is an inhibitor of DNA-dependent RNA synthesis. Incorporation of [-³²P]UTP was detected specifically in the chloroplast and mitochondrial dsRNAs, indicating that both the chloroplast dsRNAs (BDRCs) and the mitochondrial dsRNA (BDRM) of B. cinicola are RNA replicons. The green alga B. cinicola harbors different dsRNA replicons in its chloroplasts and mitochondria.     

Identification and characterization of common bean (Phaseolus vulgaris L.) lines well nodulated in the presence of high nitrate

Common bean,Phaseolus vulgaris L., is known to be ‘inefficient’ in nodulation and N₂ fixation although it responds to applied nitrogen. An experiment was conducted to identify and to characterize bean cultivars nodulating in the presence of a high level of nitrogen. Sixteen cultivars and a check for inefficient nodulation, OAC Seaforth, were inoculated and grown for 40 days in replicated pots supplied with zero, 3.5 and 10.5 mM combined nitrogen as NO ₃ ⁻ and NH ₄ ⁺ . Seven traits relating to nodulation and N₂ fixation were all significantly affected by N level (N), cultivar (Cv) and N × Cv interactions (except for root dry weight), indicating that cultivars responded differently to the N treatments. Total dry weight (W) and shoot to root ratio (S/R) increased with the increased N levels. Nodule dry weight (Wn), visual nodulation score (Nv) and nodulation index (Nx) decreased as the N increased. Percent N and N content per plant increased with the increased N level. Plant weight (W) was positively correlated with Wn, Nv and N content and negatively correlated with %N. Nodulation score was positively associated with Wn and plant N content. Genotypes superior in nodulation and N₂ fixation in the presence of N were identified. Cultivars Italian Barlotti, California Light Red Kidney, Kentucky Wonder A and Pueblo 152 were selected for further testing and use in improving the nitrate tolerant nodulating characteristic of bean.     

The nature of lectins fromDolichos lablab

The lectins from the seedsof Dolichos lablab var.lignosus (field bean) andDolichos lablab var.typicus (lablab bean) have been isolated in a homogeneous form by affinity chromatography on D-mannose linked Sepharose. Both the lectins are glycoproteins and have a molecular weight of 60,000 andS _20,w value of 5.2 and seem to be made up of 4 similar subunits (apparent molecular weight 15,000). The carbohydrate content ofthe lectins is mostly fucose (2–5 mol per mol of protein), mannose (5–8 mol per mol of protein) and N-acetyl glucosamine (1–2 mol per mol of protein). The amino acid composition of both the lectins was similar and methionine and half cystine could not be detected, Both the lectins have similar tryptic peptide map. Alanine and serine were the only N and C-terminal amino acids for both lectins. The lectins were found to contain low amounts of bound metals such as manganese, magnesium and calcium. The near ultra-violet circular dichroism spectra of the lectins are similar to that of Sainfoin. Circular dichroism data indicate that tyrosine and tryptophan residues are involved in sugar binding. The lectins are nonspecific for human blood groups and they agglutinate a variety of other erythrocytes. Among a number of sugars, D-glucose and D-mannose inhibited the haemag-glutinating activity ofthe lectins. The lectins were antigenically similar     

Diversity of viruses in Cryphonectria parasitica and C. nitschkei in Japan and China, and partial characterization of a new chrysovirus species

We surveyed native populations of the chestnut blight fungus, Cryphonectria parasitica, in Japan and China, and C. nitschkei, a sympatric species on chestnut trees in Japan, to learn more about the diversity of hypoviruses and other double-stranded (ds) RNA viruses. In a sample of 472 isolates of C. parasitica and 45 isolates of C. nitschkei from six prefectures in Japan, we found 27 containing one or more dsRNAs. Twelve isolates of C. parasitica and two isolates of C. nitschkei were infected with Cryphonectria hypovirus 1 (CHV-1); four of these 12 C. parasitica isolates also contained other dsRNAs that did not hybridize to CHV-1. In China, only one of 85 C. parasitica isolates was CHV-1-infected; no dsRNAs were detected in the other isolates from China. No other known hypoviruses were found in this study. However, we found two previously undescribed dsRNAs in Japan approximately 9 kb in size that did not hybridize to each other or to any known dsRNAs from C. parasitica. We also found three additional groups of dsRNAs, one of which represents the genome of a new member of the virus family Chrysoviridae and was found only in C. nitschkei; the other two dsRNAs were found previously in isolates of C. parasitica from Japan or China. The most significant result of this survey is the discovery of novel dsRNAs that can be characterized in future research.     

Diversity of Rhizobium-Phaseolus vulgaris symbiosis: overview and perspectives

Common bean (Phaseolus vulgaris) has become a cosmopolitan crop, but was originally domesticated in the Americas and has been grown in Latin America for several thousand years. Consequently an enormous diversity of bean nodulating bacteria have developed and in the centers of origin the predominant species in bean nodules is R. etli. In some areas of Latin America, inoculation, which normally promotes nodulation and nitrogen fixation is hampered by the prevalence of native strains. Many other species in addition to R. etli have been found in bean nodules in regions where bean has been introduced. Some of these species such as R. leguminosarum bv. phaseoli, R. gallicum bv. phaseoli and R. giardinii bv. phaseoli might have arisen by acquiring the phaseoli plasmid from R. etli. Others, like R. tropici, are well adapted to acid soils and high temperatures and are good inoculants for bean under these conditions. The large number of rhizobia species capable of nodulating bean supports that bean is a promiscuous host and a diversity of bean-rhizobia interactions exists. Large ranges of dinitrogen fixing capabilities have been documented among bean cultivars and commercial beans have the lowest values among legume crops. Knowledge on bean symbiosis is still incipient but could help to improve bean biological nitrogen fixation.     

Development of a Simple PCR-based Marker for the Determination of Growth Habit in Vicia faba L. using a Candidate Gene Approach

We have developed the first molecular marker suitable for the selection of determinate growth habit in faba bean using the candidate gene approach. We obtained the sequences of TFL1/CEN like genes from public databases and designed primers on conserved domains. We used three cultivars with determinate growth habit and four accessions (two cultivars and two lines) with indeterminate growth habit. All these genotypes are used in our faba bean breeding program. A single monomorphic PCR fragment was obtained. A set of restriction enzymes was assayed. The enzyme Hind1II produced a clear polymorphism between determinate and indeterminate genotypes. This new cleaved amplified polymorphism (CAP) marker was tested using an F₂ population contrasting for growth habit derived from the cross ‘Verde Bonita’ × 2N52. This marker showed 100% efficiency in discriminating both types of genotypes. Moreover, the codominancy of this marker allows the detection of heterozygous individuals facilitating the breeding process when pyramiding different genes. The perfect cosegregation of the marker with the trait indicates that an orthologue of TFL1/CEN controls the growth habit in faba bean. This marker has been tested in all the genotypes used in our faba bean breeding program as donors of the determinate growth habit. Therefore, it is expected to work well in all the crosses performed with these parental lines as happens in the F₂ tested. The CAPS marker developed in this work will be useful for Marker Assisted Selection programs. In addition, this marker is useful for quality control to determinate the percentage of outsider seeds in commercial seed lots. Moreover, it is a valuable tool to breeders when submitting new faba bean varieties for registration since the method allows guaranteeing that outsider plants remains under the requested limit for registration.     

Genotypic variation in biological nitrogen fixation by common bean

Field experiments were performed in Austria, Brazil, Chile, Colombia, Guatemala, Mexico and Peru as part of an FAO/IAEA Co-ordinated Research Programme to investigate the nitrogen fixing potential of cultivars and breeding lines of common bean (Phaseolus vulgaris L.). Each experiment included approximately 20 bean genotypes which were compared using the ¹⁵N isotope dilution method. Great differences in nitrogen fixation were observed between and within experiments, with average values of 35% N derived from atmosphere (% Ndfa) and highest values of 70% Ndfa being observed. These values which were larger than had been reported previously for common bean, were observed only when environmental factors were favorable. Therefore, common bean lines are available, which can support high biological nitrogen fixation. These can be used either directly as cultivars for production or in breeding programmes to enhance nitrogen fixation in other cultivars.     

Coupling- and repulsion-phase RAPDs for marker-assisted selection of PI 181996 rust resistance in common bean

The Guatemalan black bean (Phaseolus vulgaris L.) plant introduction (PI) 181996 is resistant to all known US races of the bean rust fungus Uromyces appendiculatus (Pers. ex Pers.) Unger var. appendiculatus [syn. U. phaseoli (Reben) Wint.]. We report on two random amplified polymorphic DNA (RAPD) markers OAC20₄₉₀ tightly linked (no recombinants) in coupling phase and OAE19₈₉₀ linked in repulsion phase (at 6.2±2.8 cM) to PI 181996 rust resistance. These RAPDs, generated by single decamer primers in the polymerase chain reaction, were identified in near-isogenic bulks of non-segregating resistant and susceptible BC₄F₂ (NX-040*4/PI 181996) lines. Linkage of the RAPD markers was confirmed by screening 19 BC₄F₂ and 57 BC₄F₃ individuals segregating for PI 181996 resistance. Utility of the RAPDs OAC20₄₉₀ and OAE19₈₉₀ was investigated in a diverse group of common bean cultivars and lines. All cultivars into which the PI 181996 resistance was introgressed had the RAPD OAC20₄₉₀. A RAPD similar in size to OAC20₄₉₀, observed in some susceptible common bean lines, was confirmed by Southern blotting to be homologous to the RAPD OAC20₄₉₀. Use of the RAPDs OAC20₄₉₀ and OAE19₈₉₀ in marker-assisted selection (MAS) is proposed. The coupling-phase RAPD is most useful for MAS of resistant BC_nF₁individuals during traditional backcross breeding. The repulsion-phase RAPD has greatest utility in MAS of homozygous-resistant individuals in F₂ or later-segregating generations.Mention of a trademark or a proprietary product does not constitute a guarantee or warranty of the product by the USDA and does not imply its approval to the exclusion of other products that may also be suitable.     

Rhizobium leguminosarum inoculation decreases damage to faba bean (Vicia faba) caused by broad bean mottle bromovirus and bean yellow mosaic potyvirus

Faba bean (Vicia faba) plants were inoculated with rhizobia and then their sap was infected with broad bean mottle bromovirus (BBMV) or bean yellow mosaic potyvirus (BYMV) in a field experiment. Both viral infections significantly decreased shoot and root dry weight, number of nodules, nodule dry weight, numbers of flowers and pods/plant, total plant N, grain yield and N₂ fixation. However, inoculation withRhizobium leguminosarum significantly increased all these parameters, both in healthy and virus-infected plants. Although BYMV was more destructive than BBMV, inoculation with rhizobia could be used, with other control measures, to limit damage by both viruses.The authors are with the Department of Biochemistry and Soil Science, Faculty of Agriculture, Shambat, Sudan.     

云南莲瓣兰主栽品种SSR指纹图谱的构建和遗传差异分析

为了解云南莲瓣兰(Cymbidium tortisepalum)的遗传多样性,利用SSR技术对32个莲瓣兰主栽品种进行遗传变异分析,并构建莲瓣兰栽培品种的指纹图谱。结果表明,筛选出的12对多态性高、稳定性好的引物共检测到95个等位基因,每对引物检测到4~18个等位基因,有效等位基因数(N E)为61.489,平均有效等位基因数(NA)为5.124,Shannon信息指数(I)和多态性信息含量(PIC)分别为0.806~2.624和0.789~0.953。12对引物中,以引物SSR03的等位基因数、NE、观测杂合度、I和PIC最高。32个品种在12对引物上都具有不同的特异性条带,可以彼此区别。从12对引物中筛选出3对核心引物SSR02、SSR03和SSR12构建了莲瓣兰主栽品种SSR分子指纹图谱,这3对核心引物组合即可鉴定32个莲瓣兰栽培品种。这为莲瓣兰的品种鉴定、遗传多样性分析和分子育种研究提供理论基础和技术支持。     

Cold-induced mRNAs accumulate with different kinetics in barley coleoptiles

The effect of cold treatment on gene expression in two different barley (Hordeum vulgare L.) cultivars has been studied. Cold stress induced a set of new mRNAs as determined by in-vitro translation of coleoptile RNA obtained from control and stressed seedlings. These mRNAs accumulated with different kinetics, and the cold-induced proteins could be grouped into five categories. The first category (a) is represented by a single protein with M_r of 75 kDa that reaches its highest level of expression after 6 h at 5°C. This polypeptide readily accumulates in the plant tissues and it can be detected when proteins separated by two-dimensional electrophoresis are stained with silver nitrate. The other polypeptides appear later during the 1- to 4-d stress period (protein groups b and c), increase (group d), or decrease during the period of treatment (group e). Only minor differences between the two cultivars with different cold-resistance capacities were found when the in-vitro translation products were compared. The results obtained demonstrate that several mRNAs are specifically expressed as a response to cold treatment in barley coleoptiles.Abbreviations 2-D two-dimensional - IEF isoelectrofocusing - M_r relative molecular weight - poly(A) polyadenylated - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis     

Low molecular weight subunits associated with the cytochrome b 6 f complexes from spinach and Chlamydomonas reinhardtii

Cytochrome b ₆ f complexes, prepared from spinach and Chlamydomonas thylakoids, have been examined for their content of low molecular weight subunits. The spinach complex contains two prominent low molecular weight subunits of 3.7 and 4.1 kD while a single prominent component of 4.5 kD was present in the Chlamydomonas complex. An estimation of the relative stoichiometry of these subunits suggests several are present at levels approximating one copy per cytochrome complex. The low molecular weight subunits were purified by reversed phase HPLC and N-terminal sequences obtained. Both the spinach and Chlamydomonas cytochrome complexes contain a subunit that is identified as the previously characterized petG gene product (4.8 kD in spinach and 4.1 kD in Chlamydomonas). A second subunit (3.8 kD in spinach and 3.7 kD in Chlamydomonas) appears to be homologous in the two complexes and is likely to be a nuclear gene product. The possible presence of other low molecular weight subunits in these complexes is also considered.     

Interspecific hybridization between common and tepary beans: increased hybrid embryo growth,fertility, and efficiency of hybridization through recurrent and congruity backcrossing

Cultivated common bean (Phaseolus vulgaris L.) and tepary bean (Phaseolus acutifolius A. Gray) genotypes possessing desirable agronomic traits were hybridized. The F₁ hybrids were backcrossed twice with the common bean (i.e., recurrent backcrossing). Also, alternate backcrosses with common and tepary beans (i.e., congruity backcrossing) were carried out. Embryo culture was necessary for all initial interspecific crosses, and its requirement was proportionally lower when the common bean was used as the recurrent parent and as the last parent of congruity backcrosses. Modification of the embryo culture technique was necessary to produce congruity hybrids. Effects of both tepary and common bean genotypes on the success rate of hybridization were observed. Tepary accession G 40001 and common bean cultivar ICA Pijao facilitated interspecies hybridization. Growth of hybrid embryos before rescue, recovery of mature hybrid plants, and the vigor and fertility of F₁ hybrids all increased with increased recurrent and congruity backcrosses and intermatings between male-sterile F₁ and selected fertile F₂ plants of the third and fifth congruity backcrosses. Introgression of tepary genes was verified by means of seed protein electrophoretic analysis and morphological markers. The results suggest that congruity backcrossing can help to gradually reduce or overcome P. vulgaris x P. acutifolius hybridization barriers such as genotype incompatibility, early embryo abortion, hybrid sterility, and lower frequencies of hybridization.     

Field evaluation of N2-fixation and N-utilization by phaseolus bean varieties determined by15N isotope dilution*

Summary Differences in N₂-fixation byPhaseolus vulgaris bean cultivars were successfully evaluated in the field using¹⁵N isotope dilution technique with a non-fixing test crop of a different species (wheat). The Phaseolus cultivars could have been similarly ranked for N₂-fixation capacity from either seed yield or total nitrogen yield, but the isotope method provided a direct measure of N₂-fixation and made it possible to estimate the proportion of fixed to total nitrogen in the crop and in plant parts. Amounts of nitrogen fixed varied between 24.59 kg N/ha for the 60-day cultivar Goiano precoce to 64.91 kg N/ha for the 90-day cultivar Carioca. The per cent of plant nitrogen due to fixation was 57–68% for the 90-day cultivars and 37% for Goiano precoce (60-day cultivar). Fertilizer utilization was 17–30% of a 20 kg N/ha fertilizer application. 100 kg N/ha fertilizer application decreased N₂-fixation without suppressing it totally. Differences in yield between the highest yielding (Carioca) and the lowest (Moruna) 90-day cultivars were also due apparently to varietal differences in efficiency of conversion of nitrogen to economic matteri.e. seed, as well as to differences in capacity of genotypes for N₂-fixation. The work described here was in part supported by IAEA Research Contract No. RC/2084 UNDP/IAEA Project BRA/78/006     

Nitrogen assimilation and partitioning in two nitrogen-fixing cultivars of Phaseolus vulgaris L.

Two cultivars of Phaseolus vulgaris L., one responsive (Mexico 309) and one less-responsive (Rio Tibagi) to nodulation with Rhizobium were grown in Leonard jars in a greenhouse. Bean plants were either inoculated with a strain of Rhizobium leguminosarum bv. phaseoli (UMR-1899), a vesicular-arbuscular mycorrhizal (VAM) fungus (Glomus etunicatum) or were left non-inoculated (controls). At two harvests (21 and 28 days post-emergence), extracts containing soluble proteins and free amino acids were prepared from leaves, roots and nodules of field beans. Nodulated plants contained a significantly higher concentration of protein and amino acids in all plant parts. Nitrogen-fixing beans invested a significantly greater proportion of total N as protein-N and amino acid-N as compared to VAM or control beans. Abundant nodule-specific proteins (nodulins) were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), identified and quantified using scanning densitometry. Rio Tibagi nodules contained a significantly lower concentration of glutamine synthetase (GS) subunits than did Mexico 309 nodules. Glutamate synthase (GOGAT) and GS activities were low relative to other legumes. The transferase/synthetase ratio for GS was also low indicating that the synthetase activity was caturated and was operating at maximal level in these young N₂-fixing associations. Specific nodule activity (SNA) and the level of GS were correlated (r=0.90, p<0.05) for both cultivars at both harvests. GS activity was only 8 or 24% higher than SNA in nodules of Mexico 309 or Rio Tibagi cultivars, respectively, under conditions where substrate was not limiting. This suggests that early in the functioning of this symbiosis N assimilation by GS is the rate-limiting step in N₂ fixation by these two bean cultivars, each with a different symbiotic efficiency. Phaseolus breeding programs that attempt to improve N₂ fixation in beans should identify germplasm that expresses elevated levels of nodule-specific GS or GOGAT, and this material should be used along with effective R. leguminosarum bv. phaseoli strains that have already been selected, to determine superior host-microsymciont associations.     

Association of particles that contain double-stranded RNAs with algal chloroplasts and mitochondria

Linear dsRNAs (double-stranded RNAs) belonging to several distinct size classes were found to be localized in chloroplasts and mitochondria of Bryopsis spp., raising the possibility that these dsRNAs are prokaryotic in nature. The algal cytosol and nuclei did not contain dsRNAs. The amount of the dsRNAs in the organelles appeared constant, and there were about 500 copies per chloroplast. The four major dsRNAs from Bryopsis chloroplasts were about 2 kbp (kilobase pairs) in length and originated from discrete isometric particles of about 25 nm diameter. These virus-like particles were purified by CsCl density gradient centrifugation after extraction from isolated chloroplasts with chloroformbutanol and subsequent precipitation with polyethylene glycol. They had a buoyant density of about 1.40 g · cm^–3 and contained four major and three minor proteins. Mitochondrial dsRNAs were about 4.5 kbp in length and formed less-stable particles of about 40 nm in diameter with a buoyant density of 1.47 g · cm^–3. Some observations support the hypothesis that vertical transmission of the protein-coated, non-infectious dsRNAs occurs within cell organelles. Double-stranded RNAs of various sizes were found in most green, red, and brown algae. The characteristics of the algal dsRNAs are compared with those of dsRNAs from higher plants and the biological significance of the dsRNAs in cell organelles is discussed.Abbreviations dsRNA double-stranded RNA - kbp kilobase pairs - SDS sodium dodecyl sulfate - SSC 0.15 M NaCl 0.015 M sodium citrate - PAGE polyacrylamide gel electrophoresis The authors would like to express their gratitude to Dr. T. Natsuaki, Utsunomiya University, and Dr. D. Hosokawa, Tokyo University of Agriculture and Technology, for their helpful suggestions throughout this research. They are also much indebted to Dr. B. Wang, Institute of Genetics, Academia Sinica, Beijing, PRC, for his suggestions on rice dsRNA, and to Dr. T. Kohbara, Senshu University, on Bryopsis cells. Sincere thanks are also due to Dr. T. Misonou, Yamanashi University, and Dr. K. Masuda, Akita Prefectural College of Agriculture, for supplying plant materials; to Dr. N. Sonoki, Azabu University, for nucleotide analysis of dsRNAs; and to Y. Koshino for technical assistance. This research was supported in part by a Grant-in-Aid from the Ministry of Education, Science and Culture of Japan.     

Inheritance of two endosperm protein loci in rice (Oryza sativa L.)

Summary Previous studies indicated two types of phenotypic protein markers as two minor bands of SDS-PAGE for rice storage protein. A variant derived from a Pakistani variety, Dular, was found to show a mobility variant with Band 11, a relatively faster-moving band as compared to Band 10, while most of the other cultivated rices exhibited Band 10 at a molecular weight of around 100–110 K. Band 11 was also observed in several wild rice species. How this variant occurred is not known. Another marker is characterized by the presence of either Band 56 (slower-migrating band) or Band 57 (faster-migrating band) in most cultivars at a molecular weight of about 28–27 K. Most indica varieties developed in Taiwan have Band 57 and japonica varieties have Band 56. Genetic analysis of F₁, F₂ and F₃ seeds from interstrain crosses indicated that Band 10 versus Band 11 and Band 56 versus Band 57 are due to codominant alleles at two loci. Tests of independent inheritance between these two loci (Band 10/11 versus Band 56/57) indicated that there is no linkage between them. Both of these two protein loci encode for endosperm proteins and mostly belong to the minor polypeptide subunits of the glutelin fraction of rice seed proteins. Studies on reciprocal crosses indicate dosage effects as exhibited in band patterns. Variations in band intensity were frequently observed when the maternal genotype was different.     

Breding common bean for improved biological nitrogen fixation

Common bean (Phaseolus vulgaris L.), which is an important food crop in the Americas, Africa and Asia, usually is thought to fix only small amounts of atmospheric nitrogen. However, field data indicate considerable genetic variability for total N₂ fixation and traits associated with fixation. Studies have shown that selection to increase N₂ fixation will be successful if: (1) discriminating traits (selection criteria) are measured precisely, (2) variability in germplasm is heritable, (3) selected parents are also agronomically suitable, (4) units of selection facilitate quantification of selection criteria, and (5) a breeding procedure that allows maximum genetic gain for N₂ fixation and recombination with essential agronomic traits is chosen. Breeding lines capable of fixing enough atmospheric N₂ to support seed yields of 1000–2000 kg ha^–1 have been identified and new cultivars with high N₂ fixation potential are being released.     

Import of peroxisomal hydroxypyruvate reductase into glyoxysomes

A new procedure was used to purify the peroxisomal matrix enzyme hydroxypyruvate reductase (HPR) from green leaves of pumpkin (Cucurbita pepo L.) and spinach (Spinacia oleracea L.). Monospecific antibodies were prepared against this enzyme in rabbits. Immunoprecipitation of HPR from watermelon (Citrullus vulgaris Schrad.) yielded a single protein with a subunit molecular weight of 45 kDa. Immunohistochemical labeling of HPR was found exclusively in watermelon microbodies. Isolated polyadenylated mRNA from light-grown watermelon cotyledons was injected into Xenopus laevis oocytes. The heterologous in-vivo translation product of HPR exhibited the same molecular weight as the immunoprecipitate from watermelon cotyledons, indicating the lack of a cleavable extra sequence. The watermelon HPR translated in oocytes was imported into isolated glyoxysomes from castor bean (Ricinus communis L.) endosperm and remained resistant to proteolysis after the addition of proteinase K. The HPR did not change its apparent molecular weight during sequestration; however, it may have changed its conformation.Abbreviations HPR hydroxypyruvate reductase - PMSF phenylmethylsulfonyl fluoride - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis