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PubMed1995

Comparison of electric and growth responses to excision in cucumber and pea seedlings. II. Long-distance effects are caused by the release of xylem pressure.

Excision of a growing stem causes local wound responses, such as membrane depolarization and growth inhibition, as well as effects at larger distances from the cut. In this study, cucumber hypocotyls were excised 100 mm below the hook, so that the growing region was beyond the reach of the wound-induced depolarization (up to 40 mm). Even at such a distance, the cut still caused a considerable and rapid drop in the hypocotyl growth rate. This growth response is not a direct wound response because it does not result from the cut-induced depolarization and because it can be simulated by root pressure manipulation (using a pressure chamber). The results indicate that the growth response resulted from the rapid release of the xylem pressure upon excision. To test this conclusion we measured the xylem pressure by connecting a pressure probe to the cut surface of the stem. Xylem pressure (Px) was found to be +10 to +40 kPa in cucumber hypocotyls and -5 to -10 kPa or lower in pea epicotyls. Excision of the cucumber hypocotyl base led to a rapid drop in Px to negative values, whereas excision in pea led to a rapid rise in Px to ambient (zero) pressure. These fast and opposite Px changes parallel the excision-induced changes in growth rate (GR): a decrease in cucumber and a rise in pea. The sign of the endogenous xylem pressure also determined whether excision induced a propagating depolarization in the form of a slow wave potential (SWP). Under normal circumstances pea seedlings generated an SWP upon excision whereas cucumber seedlings failed to do so. When the Px in cucumber hypocotyls was experimentally inverted to negative values by incubating the cumber roots in solutions of NaCN or n-ethylmaleimide, excision caused a propagating depolarization (SWP). The experiment shows that only hydraulic signals in the form of positive Px steps are converted into propagating electric SWP signals. These propagating depolarizations might be causally linked to systemic 'wound' responses, which occur independently of the short-distance or direct wound responses.

Cucumis sativus↗

PubMed2000

Gravimorphogenesis of Cucurbitaceae plants: development of peg cells and graviperception mechanism in cucumber seedlings.

We examined the effect of microgravity on the peg formation of cucumber seedlings for clarifying the mechanism of gravimorphogenesis in cucurbitaceous plants. The spaceflight experiments verified that gravity controls the formation of peg, hypocotyl hook and growth orientation of cucumber seedlings. Space-grown cucumber developed a peg on each side of the transition zone of the hypocotyl and root, indicating that on the ground peg formation is regulated negatively by gravity (Takahashi et al. 2000). It was found that the auxin-regulated gene, CS-IAA1, was strongly expressed in the transition zone where peg develops (Fujii et al. 2000). In the seedlings grown horizontally on the ground, CS-IAA1 transcripts were much abundant on the lower side of the transition zone, but no such differential expression of CS-IAA1 was observed in the space-grown cucumber (Kamada et al. 2000). These results imply that gravity plays a role in peg formation through auxin redistribution. By the negative control, peg formation on the upper side of the transition zone in the horizontally growing seedlings might be suppressed due to a reduction in auxin concentration. The threshold theory of auxin concentration accounted for the new concept, negative control of morphogenesis by gravity (Kamada et al. 2000). Anatomical studies have shown that there exists the target cells destined to be a peg and distinguishable at the early stage of the growth. Ultra-structural analysis suggested that endoplasmic reticulum develops well in the cells of the future peg. Furthermore, it was found that reorganization of cortical microtubules is required for the change in cell growth polarity in the process of peg formation. The spaceflight experiment with cucumber seedlings also suggested that in microgravity positive hydrotropic response of roots occurred without interference by gravitropic response (Takahashi et al. 1999b). Thus, this spaceflight experiment together with the ground-based studies has shown that cucumber seedling is an ideal for the study of gravimorphogenesis, hydrotropism and their interaction. Although peg formation is seen specifically in cucurbitaceous seedlings, it involves graviperception, auxin transport and redistribution and cytoskeletal modification for controlling cell growth polarity. This system could be a useful model for studying important current issues in plant biology.

Cucumis sativus↗

PubMed2006

[Induction of cucumber hairy roots and effect of cytokinin 6-BA on its growth and morphology].

Hairy roots of Cucumis sativus L. could be incited directly from the cut edges of 10-day-old cotyledon explants after infection with the strain Agrobacterium rhizogenes ATCC15834 harboring agropine-type plasmid, pRiA4b for 5 days. It was observed that the percentage of rooting cotyledon explants was more than 90 % 10 days after infection. Hairy roots could grow rapidly and highly branched on solid plant growth regulator-free MS medium. The PCR amplification of rol B genes and vir C gene showed that T-DNA of Ri plasmid of A. rhizogenes was integrated and expressed into the genome of transformed cucumber hairy roots. A bacterium-free transformed cucumber hairy root line was selected to culture on solid MS medium to examine influence of exogenous cytokinin 6-BA on growth and morphology alteration of cucumber hairy roots. The results showed that cytokinin 6-BA can influence the growth and altered the morphology of hairy roots. With increasing of 6-BA concentrations, Cucumber hairy roots become shorter and thicker and less branched. 6-BA at the concentration of 0.1 to approximately 3.0 mg/L could delay the appearance of maximum growth peak by 5 days and decreased the content of soluble protein, enhanced the activities of SOD and POD and decreased the levels of endogenous ethylene evolution in cucumber hairy roots. Our results also indicated that cytokinin 6-BA in the medium could influence growth and morphology alternation of cucumber hairy roots and delay its senescence of hairy roots by acting through ethylene.

Cucumis sativus↗

PubMed2006

[The role of serine endopeptidase in cucumber leaf senescence].

The role of serine endopeptidase in cucumber leaf senescence was studied by using the inhibitor of serine endopeptidase and plant growth regulators (6-BA and ABA) on darkness-induced cucumber leaves. The results showed that the senescence of cucumber leaves were delayed by AEBSF [4-(2-aminoethyl) benzenesulfonyl fluoride hydrochloride], an inhibitor of serine-type endopeptidase, or 6-BA treatment. The chlorophyll contents increased by AEBSF (Fig.3) and the protein degradation of leaves under AEBSF treatment declined more slowly than in the control or under ABA 50 micromol/L treatment (Fig.4), partly because the activities of serine endopeptidases became lower during senescence. However, the activities of endopeptidase in cucumber leaf were increased by ABA 50 micromol/L (Fig.2A), furthermore, the MDA content were also influenced by AEBSF and plant growth regulators (Fig.5). Native gradient PAGE showed that six bands of isoenzymes were detected in cucumber leaves and four bands of which were the type of serine-endopeptidase (Fig.1), and proved that the activities of serine-endopeptidase were inhibited by AEBSF, but enhanced by ABA (Fig.2B) in the leaves. It implies that serine endopeptidases might play an important role in cucumber leaf senescence.

Abscisic Acid↗

PubMed1984

Interaction of sea cucumber saponins with multilamellar liposomes.

The effect of three sea cucumber saponins, echinoside A, bivittoside D and holothurin A, on multilamellar liposomes was investigated. An ideal osmotic behavior of liposomes was described as a linear relationship between the reciprocal 3/2 s power of absorbance at 450 nm and the osmotic gradient across the membrane. Sea cucumber saponins at concentrations below critical micelle concentration (CMC) disturbed this linear relationship in liposomes composed of egg phosphatidylcholine, phosphatidic acid and cholesterol. Cholesterol-free liposomes were not susceptible to these saponins. Results of optical measurements were consistent with those of transmission electron microscopy, which showed saponin-induced changes in liposomal structure. The lytic activity of sea cucumber saponins on liposomes depended on their chemical structure. These results suggest that sea cucumber saponins as monomers can interact with liposomes and that cholesterol serve as a principal binding site for the sea cucumber saponins.

Animals↗

PubMed1999

Fatty acid compositions in local sea cucumber, Stichopus chloronotus, for wound healing.

Fatty acid profile from crude extracts of local sea cucumber Stichopus chloronotus was determined using gas chromatography (GC) technique. The extracts were prepared separately in methanol, ethanol, phosphate buffer saline (PBS), and distilled water as part of our study to look at the affinity of these solvents in extracting the lipid from sea cucumber. The PBS and distilled water extractions indicate water-soluble components, while the organic fractions are extracted in methanol and ethanol as organic solvents. Furthermore, water extraction is the conventional method practiced in Malaysia. In our analysis the C14:0 (myristic), C16:0 (palmitic), C18:0 (stearic), C18:2 (linoleic), C20:0 (arachidic), and C20:5 (eicosapentaenoic, EPA) were significantly different (p < 0.01) in the four solvent extractions. However, the PBS extraction contained a much higher percentage of EPA (25.69%) compared to 18.89% in ethanol, 7.84% in distilled water, and only 5.83% in methanol, and variances were significantly different (p < 0.01 ). On the other hand, C22:6 (docosahexaenoic acid or DHA) is much higher in water extraction (57.55%), in comparison to the others where only 3.63% in PBS and 1.20% in methanol, and this difference is significant at p < 0.01. No DHA was detected in ethanol extractions. Subsequently, C18:1 (oleic acid) was only detected in PBS (21.98%) and water extraction (7.50%). It is interesting that palmitic acid, C16:() was higher in methanol (20.82%) and ethanol (2.18%), while 12.55% was detected in PBS and only 2.20% in water extraction: and again this was significantly different at p < 0.01. Although our results have shown that all four solvents were different in terms of their ability to extract fatty acids, the major component for tissue repair was well preserved. Probably this is one of the important precocious steps when working with a delicate sea cucumber, in both experimental and/or at the preparative stages. Freshness of the sea cucumber samples is important when undertaking this type of experiment. Finally, we believe that the local sea cucumber S. chloronotus contains all the fatty acids required to play a potential active role in tissue repair.

Animals↗

PubMed2006

Isolation of sphingoid bases of sea cucumber cerebrosides and their cytotoxicity against human colon cancer cells.

Sea cucumber is a health-beneficial food, and contains a variety of physiologically active substances including glycosphingolipids. We show here the sphingoid base composition of cerebrosides prepared from sea cucumber and the cytotoxicity against human colon cancer cell lines. The composition of sphingoid bases prepared from sea cucumber was different from that of mammals, and the major constituents estimated from mass spectra had a branched C17-19 alkyl chain with 1-3 double bonds. The viability of DLD-1, WiDr and Caco-2 cells treated with sea cucumber sphingoid bases was reduced in a dose-dependent manner and was similar to that of cells treated with sphingosine. The sphingoid bases induced such a morphological change as condensed chromatin fragments and increased the caspase-3 activity, indicating that the sphingoid bases reduced the cell viability by causing apoptosis in these cells. Sphingolipids of sea cucumber might therefore serve as bioactive dietary components to suppress colon cancer.

Animals↗

PubMed2005

Isolation of a partial sequence of a putative nucleotide sugar epimerase, which may involve in stamen development in cucumber (Cucumis sativus L.).

Sex determination is the most widely studied subject in cucumber. The sex of cucumber plants can be monoecious, hermaphrodite, gynoecious, androecious, or andromonoecious. Besides environmental factors, three major genes, F/f, M/m, and A/a mainly govern the sex types in cucumber. Regardless of their sex all floral buds are bisexual at the early bud stage. A stage specific arrest of either stamen or carpel leads to unisexual flower development. The possible downstream product of the interaction of the sex determining genes that may directly allow the growth or selectively arrest stamen or pistil is not yet identified. Therefore, in the current study, we performed suppression subtractive hybridization using floral buds from nearly isogenic gynoecious and hermaphrodite cucumber plants and identified for the first time a cDNA homologous to nucleotide sugar epimerase. The expression level of the isolated putative nucleotide sugar epimerase is weak in female floral buds but strong in bisexual and male flowers. The weak level of the putative nucleotide sugar epimerase may be an indication for its improper functioning, which may influence stamen development in cucumber plants.

Blotting, Southern↗

PubMed2003

Mosaic (MSC) cucumbers regenerated from independent cell cultures possess different mitochondrial rearrangements.

Passage of the highly inbred cucumber ( Cucumis sativus L.) line B through cell culture produces progenies with paternally transmitted, mosaic (MSC) phenotypes. Because the mitochondrial genome of cucumber shows paternal transmission, we evaluated for structural polymorphisms by hybridizing cosmids spanning the entire mitochondrial genome of Arabidopsis thaliana L. to DNA-gel blots of four independently generated MSC and four wild-type cucumbers. Polymorphisms were identified by cosmids carrying rrn18, nad5-exon2, rpl5, and the previously described JLV5 deletion. Polymorphisms revealed by rrn18 and nad5-exon2 were due to one rearrangement bringing together these two coding regions. The polymorphism revealed by rpl5 was unique to MSC16 and was due to rearrangement(s) placing the rpl5 region next to the forward junction of the JLV5 deletion. The rearrangement near rpl5 existed as a sublimon in wild-type inbred B, but was not detected in the cultivar Calypso. Although RNA-gel blots revealed reduced transcription of rpl5 in MSC16 relative to wild-type cucumber, Western analyses revealed no differences for the RPL5 protein and the genetic basis of the MSC16 phenotype remains enigmatic. We evaluated 17 MSC and wild-type lines regenerated from independent cell-culture experiments for these structural polymorphisms and identified eight different patterns, indicating that the passage of cucumber through cell culture may be a unique mechanism to induce or select for novel rearrangements affecting mitochondrial gene expression.

Cells, Cultured↗

PubMed1992

Transformation of cucumber tissues by microprojectile bombardment: identification of plants containing functional and non-functional transferred genes.

The microprojectile bombardment method was used to transfer DNA into embryogenic callus of cucumber (Cucumis sativus), and stably transformed cucumber plant lines were obtained. A total of 107 independently regenerated cucumber plants were assayed for the presence and expression of the transferred Nos-NPTII gene (encoding nopaline synthase-neomycin phosphotransferase II). Genomic blot hybridization analyses showed that a high percentage (16%) of the cucumber plants were transformed with Nos-NPTII; however, only about 25% of these transgenic plants expressed Nos-NPTII. Inactivity of Nos-NPTII in many of the transformed cucumber plants may be associated with the transfer of multiple copies of Nos-NPTII. PCR and genomic blot hybridization analyses were used to show that the transferred gene was inherited in the subsequent plant generation.

Amino Acid Oxidoreductases↗

PubMed2026

Deciphering differential mRNA and lncRNA expression profiles in response to PEG simulated drought stress in cucumber (Cucumis sativus L.).

Cucumber (Cucumis sativus L.), a vital fruit vegetable of the Cucurbitaceae family, originated in India ∼ 3000 years ago. It is widely used in the culinary, therapeutic, and cosmetic sectors. Cucumber cultivation is significantly impacted by drought stress, especially in arid and semi-arid regions. This study investigates the molecular response to drought using two contrasting cucumber lines: WBC-23-2 (drought-tolerant) and DGPC-59 (drought-sensitive). Drought was simulated using polyethylene glycol (PEG), and effects on physiological and biochemical traits were evaluated. The tolerant line exhibited reduced leaf wilting and higher relative water content (RWC). Based on these physiological markers, transcriptomic profiling was employed to identify the underlying regulatory networks. Analysis identified 4,736 DEGs, suggesting that the tolerant line's superior resilience is driven by preferential activation of genes involved in photosynthesis and glutathione metabolism. Conversely, the sensitive genotype showed enrichment in organonitrogen compound catabolism and water deprivation response. This divergence is further reflected in the regulation of 155 transcription factors (TFs) across various families, indicating distinct regulatory architectures between the two lines. Additionally, 774 drought-responsive long non-coding RNAs (lncRNAs) were identified, acting via cis, trans, and competing endogenous RNA (ceRNA) mechanisms to modulate gene expression. Key candidate genes associated with drought tolerance included WAT1-related protein At5g64700, thaumatin-like protein, berberine bridge enzyme-like 18, probable WRKY transcription factor, and pathogenesis-related protein 1. This study reveals a complex regulatory network of mRNAs, lncRNAs, and TFs underlying drought response and provides a valuable foundation for breeding drought-resilient cucumber cultivars. A web-based genomic resource, CsDTDb, has been developed and made publicly available to facilitate future functional genomics studies related to drought tolerance in cucumber.

DEGs↗

PubMed2004

Molecular cloning, characterization, tissue-specific and phytohormone-induced expression of calcium-dependent protein kinase gene in cucumber (Cucumis sativus L.).

A cucumber cDNA designated CsCPK5 and encoding a calcium-dependent protein kinase (CsCDPK5) was isolated and characterized. An open reading frame of 1542 bp was detected that could encode a protein of 514 amino acid residues with a calculated molecular mass of 56.5kDa. Comparison of the deduced amino acid sequence of CsCDPK5 with sequences of other CDPKs revealed the highest similarity (85%) to AtCDPK6. As described for other CDPKs, CsCDPK5 has a long variable domain preceding a catalytic domain, an autoinhibitory function domain, and a C-terminal calmodulin-domain containing 4 EF-hand calcium-binding motifs. The N-terminal long variable domain of CsCDPK5 does not contain the N-myristoylation motif, which is found in many CDPKs. The relative expression level of the CsCPK genes in various organs of cucumber plants and seedlings and in etiolated, excised cotyledons and hypocotyls following treatments with light and/or benzyladenine (BA), abscisic acid (ABA), gibberellic acid (GA) or indole acetic acid (IAA) was determined by northern analysis using the CsCPK5 cDNA probe. The CsCPK transcripts are most abundant in cucumber plant Leaves with less accumulation in cucumber seedling roots and hypocotyls and lowest Levels in cucumber plant flowers and seedling hooks and cotyledons. All phytohormones tested enhanced the accumulation of the transcripts 2-3-fold in etiolated cotyledons. On the other hand, levels of the transcripts increased to a lesser extent in both light and BA- or IAA-treated cotyledons and no effect was noted in response to light treatment with GA. In hypocotyls, no major changes in the relative levels of CsCPK transcripts were observed in the phytohormone-treated etiolated and light-exposed tissues, except an up-regulatory effect with IAA treatment in the etiolated and IAA, ABA and GA treatments in light-exposed hypocotyls. These observations suggest that exogenous phytohormones can up-regulate the CsCPK transcript levels in tissue-specific, and light-dependent and independent manners.

Amino Acid Sequence↗

PubMed1997

A cDNA encoding a putative SPF1-type DNA-binding protein from cucumber.

A cDNA clone encoding a polypeptide with homology to the novel SPF1 DNA-binding protein of sweet potato has been isolated from a cDNA library from RNA of senescing cucumber (Cucumis sativus, L.) cotyledons. Comparison of the two sequences reveals similar features which may be important in the evolution and function of this protein, including a duplicated region of about 56 amino acids (aa). The first half of the duplicated region is enriched in basic aa and is very highly conserved, both within and between each polypeptide. In contrast, the second half of the duplicated region is poorly conserved within each polypeptide, but highly conserved when cucumber and sweet potato sequences are compared. Southern blot analysis with cucumber DNA shows a simple hybridisation pattern indicating one or very few genes. Northern blot analysis shows that the expression of the cucumber gene increases in cotyledons as they expand and become photosynthetic and remains high in senescence. The possibility that the cucumber SPF1-type protein may be involved in carbohydrate regulation of gene expression is discussed.

Amino Acid Sequence↗

PubMed2002

Fresh cucumber flavor in refrigerated pickles: comparison of sensory and instrumental analysis.

The ability of nonacidified, refrigerated pickled cucumbers to produce the fresh cucumber flavor impact compounds (E,Z)-2,6-nonadienal and (E)-2-nonenal declined during storage. Production of these compounds decreased as the pH of refrigerated cucumbers was reduced. Despite the fact that the concentrations of (E,Z)-2,6-nonadienal and (E)-2-nonenal generated were over 10(5)-fold greater than the threshold levels, it was possible for a sensory panel to consistently detect differences in the intensity of fresh cucumber flavor, provided the pH difference between samples was 1 unit or greater. The presence of spices did not interfere with the ability of panelists to detect differences in fresh flavor intensity. There was a linear correlation between sensory scores and the amount of (E,Z)-2,6-nonadienal produced by cucumbers equilibrated at different pH levels.

Aldehydes↗

PubMed2002

Biological control of cucumber and sugar beet damping-off caused by Pythium ultimum with bacterial and fungal antagonists.

AIMS: Five bacterial strains belonging to Bacillus subtilis, Pseudomonas fluorescens and Ps. corrugata and two fungal strains belonging to Trichoderma viride and Gliocladium virens were evaluated for their efficacy in controlling sugar beet and cucumber damping-off caused by Pythium ultimum. METHODS AND RESULTS: The in vitro antagonistic activity of bacteria against various Pythium spp. was evaluated with dual cultures in various media. Pseudomonas strains inhibited the pathogen better than Bacillus strains. To identify potentially useful antagonist combinations, dual compatibility of antagonists was also evaluated, based on growth in two liquid media containing substrate previously used by other antagonists. Four pairs of bacteria were selected. Sugar beet damping-off biocontrol was attempted with bacterial seed treatments (individually and in pairs). Cucumber damping-off biocontrol was attempted with bacterial seed treatments and bacterial and fungal compost treatments. In sugar beet, satisfactory biocontrol was only achieved with Pseudomonas antagonists. Antagonist combinations did not show any superior biocontrol ability to individual antagonists and compatibility of bacteria in vitro did not correlate with compatibility in vivo. Bacterial seed treatments and fungal compost treatments failed to control cucumber damping-off. Better biocontrol in cucumber was achieved when bacterial antagonists were applied by drenching or by coating seed with bacteria in a peat carrier. CONCLUSIONS: Pseudomonas antagonists were superior to Bacillus antagonists in controlling damping-off in cucumber and sugar beet. Pseudomonas peat inocula maintained a good shelf-life 2 years after preparation. SIGNIFICANCE AND IMPACT OF THE STUDY: Pseudomonas peat formulations have the potential for development into commercial biopesticides.

Bacillus subtilis↗

PubMed1998

Induction of systemic resistance to Pythium damping-off in cucumber plants by benzothiadiazole: ultrastructure and cytochemistry of the host response.

Benzo (1,2,3) thiadiazole-7-carbothioic acid S-methyl ester (BTH, CGA 245704), a non-toxic, synthetic chemical, was applied as a foliar spray to cucumber plants and evaluated for its potential to induce defense mechanisms in root tissues infected by the soilborne pathogen, Pythium ultimum Trow. In non-treated cucumber plants, fungal colonization was intense and paralleled marked host tissue damage, whereas in BTH-treated plants, pathogen ingress towards the vascular stele was apparently halted by the massive deposition of a phenolic-enriched material which occluded a large number of cortical and vascular parenchyma cells. This considerable increase in the accumulation of phenolics was accompanied by cytological disorders of the invading pathogen at a time when the wall-bound cellulose component was preserved. In addition to phenolic compounds, the occluding material contained large amounts of beta-glucoside residues. These residues gradually decreased in the areas neighboring fungal cells whereas phenolic deposition appeared to be more uniformly distributed throughout the occluded host cells. Pathogen penetration in non-occluded cucumber root cells coincided with other changes, mainly characterized by both the deposition onto the inner surface of the cell walls of some heterogeneous wall appositions and the coating of some intercellular spaces with an electron-opaque material. Evidence is provided in this study that BTH has the ability to induce SAR in cucumber. Exogenous, foliar applications of the chemical sensitize susceptible cucumber plants to react more rapidly and more efficiently to P. ultimum attack, mainly through the massive accumulation of phenolic compounds at sites of attempted pathogen penetration.

Journal Article↗

PubMed1986

RNA-directed RNA polymerases from healthy and from virus-infected cucumber.

Much work has been done on the isolation, purification, and characterization of the RNA-directed RNA polymerase (EC 2.7.7.48) of cucumber mosaic virus (CMV)-infected cucumbers. Uninfected plants were reported to have no such enzyme, but we recently detected low levels of the activity in cucumber. Since tobacco and cowpea contain such an enzyme that is variably increased in amount by various virus (as well as viroid) infections, we assumed that this would also be the case upon CMV infection of cucumber. However, further purification and characterization of the RNA-directed RNA polymerases from healthy and from infected cucumber suggests that these are different enzymes. The presumed CMV replicase was obtained pure and consists of a major polypeptide of Mr 100,000 and minor components of Mr 110,000 and about 10,000. The Km is 5 microM ([3H]GTP) when tobacco mosaic virus RNA is used as template.

Molecular Weight↗

PubMed2000

Overexpression, enzymatic properties and tissue localization of a ferrochelatase of cucumber.

Ferrochelatase catalyzes the insertion of Fe2+ into protoporphyrin IX to generate protoheme. A putative mature region of a cucumber ferrochelatase cDNA (hemH) was overexpressed in Escherichia coli and purified to homogeneity (40 kDa). The optimum pH was 7.7, and the apparent K(m) values for deuteroporphyrin IX and Fe2+ were 14.4 microM and 4.7 microM, respectively. The activity of the ferrochelatase was inhibited by N-methylprotoporphyrin IX (I50 = 4 nM). Western blot analysis with a polyclonal antibody raised against the recombinant ferrochelatase showed that the antibody crossreacted with protein extracts from hypocotyls and roots of cucumber but not with that from cotyledons. The antibody did not crossreact with proteins of thylakoid membranes of chloroplasts in cucumber cotyledons, although the ferrochelatase activity was mainly associated with the thylakoid membranes. Northern blot analysis also indicated that the hemH gene was expressed mainly in hypocotyls and roots, but little in cotyledons, and the level of the hemH transcripts was not light-responsive. These results demonstrated that the cucumber hemH gene encodes a ferrochelatase which presumably functions for heme biosynthesis in non-photosynthetic tissues, such as hypocotyls and roots, and suggested the presence of other types of ferrochelatase in cucumber, one of which is located in thylakoid membranes of chloroplasts.

Animals↗