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(1984) Microanalysis of plant mitochondrial protein ..

(1988) Microsomal protein synthesis inhibition: an early mani-festation of gentamicin nephrotoxicity.

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Microanalysis of plant mitochondrial protein synthesis products: ..

Whether the pressure gradient is sufficiently steep is a more vexing question. The pressure gradient required to drive phloem translocation at observed rates is determined by the transport resistance of the phloem path, according to Ohm’s Law. Dimensions of the sieve pores set a limiting radius for volume flux of transported sap (Equation 5.3) and hence transport resistance. If the sieve pores were open and unoccluded by P-protein, a number of studies have demon-strated that the measured pressure gradients are sufficient to support the observed rates of flow. However, the in situ radii of sieve pores remain unknown.

 Spiegelman S, Kamen MD. 1946. Genes and nucleoproteins in the synthesis of enzymes.  104: 581-84

The mutant cells can utilize arginine for protein biosynthesis and show normal growth only when this amino acid is supplied in the medium. Further studies show that not all mutants of Neurospora defective in the capacity to make arginine are identical; they differ with respect to the specific step in the pathway of arginine biosynthesis that is genetically defective.

Microanalysis of plant mitochondrial protein ..

Neuberger A. 1938. Carbohydrates in protein the carbohydrate component of crystalline egg albumin.  32: 1435-51

In contrast to photoassimilate uptake from phloem apoplasm, very little is known about the mechanism of sugar efflux into the apoplasm until very recently. Estimates of photoassimilate flux to phloem apoplasm, based on rates of sucrose export from leaves, suggest that this transport event must be facilitated by other transport processes (van Bel 1993). This is now confirmed by the recent cloning of sucrose efflux protein that sheds a light on the molecular mechanisms of phloem loading (Chen et al. 2012).

Phloem unloading describes transport events responsible for assimilate movement from se–cc complexes to recipient sink cells. A distinction must be made between transport across the se–cc complex boundary and subsequent movement to recipient sink cells. The former transport event is termed sieve element unloadingand the latter post-sieve element transport. On reaching the cytoplasm of recipient sink cells, imported photoassimilates can enter metabolic pathways or be compartmented into organelles (e.g. amyloplasts, protein bodies and vacuoles). Metabolic fates for photoassimilates include catabolism in respiratory pathways, biosynthesis (maintenance and growth) and storage as macromolecules (starch and fructans).

Microanalysis of plant mitochondrial protein synthesis products:.

The rationale for such an approach relies on the pathophysiological mechanisms controlling the renal handling of plasmaproteins.

Concerning the evolution of plant Rf, the tandem gene cluster of bvORF18, bvORF19, bvORF20, and bvORF21 is reminiscent of the organization of the Rf loci of petunia, radish, and rice, whose translation products are PPR proteins (; ; ; ; ; ; ). The evolutionary significance of such gene clusters may lie in the increased allelic diversity (). We should point out an additional similarity that, in both PPR-type Rf loci and the sugar beet Rf1 locus, not all copies but one or several of these are capable of restoring fertility. Therefore, it is possible that a common mechanism has played an important role in the evolution of plant Rfs. We are currently investigating the organizational diversity of Rf1 in B. vulgaris plants to see how these genes have evolved.

An important question that relates to the significance of macromolecules in the contents of sieve tubes is proof that they are translocated and that translocation is essential for their function at a sink. A diversity of studies that have exploited cucurbit root stocks and grafted scions has provided clear evidence that P proteins among others are graft transmissible. In a series of elegant experiments Aoki et al. (2005) labelled and injected two isolated pumpkin phloem proteins (CmPP16‑1 and CmPP16-2) into the vasculature of intact rice plants through severed leaf hopper stylets and showed their translocation as well as some evidence for specificity in protein translocation. The Flowering Locus T (FT) protein formed in leaves mediates the flowering transition of shoot apical meristems and the evidence that it is translocated is compelling. The long distance movement of RNA molecules was first demonstrated for plant viruses and there is now good evidence for phloem translocation of a number of transcripts (Lough and Lucas 2006). A recent compilation identified 13 miRNAs involved in plant responses to drought/salt stress (Covarrubias and Reyes 2010). Eight of these were identified in lupin phloem exudate (Rodriguez-Medina et al. 2011) and, importantly, six were also recovered from PCR amplification of apple stylet exudate (Varkonyi-Gasic et al 2010). There is thus a possibility that the responses to drought and salinity are mediated through miRNAs translocated from sites where the stress is sensed to sites where a response is initiated.

Ochoa S, Stern JR, Schneider MC. 1951. Enzymatic synthesis of citric acid—crystalline condensing enzyme.  193: 691-702
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    Skinner MK, Griswold MD. 1980. Sertoli cells synthesize and secrete transferrin-like protein. 255: 9523-25

  • Inflammation, Atherosclerosis, and Coronary Artery Disease

    Stanley WM. 1935a. Isolation of a crystalline protein possessing the properties of tobacco-mosaic virus. 81: 644-45

  • 05/02/2002 · Mitochondrial protein ..

    The protein synthesis in the very first cells must have already depended on the ..

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Preliminary analysis of the cauliflower mitochondrial …

For some plant species, sieve-pore sealing develops slowly, or can be experimentally down-regulated by massage or repeated excisions (Milburn and Kallarackal 1989) or slowed by puncturing the vasculature while it is snap frozen in liquid N2 (Pate et al 1984). Carefully placed incisions that do not disturb the underlying xylem, which in any case is more likely to be under tension, permit collection of relatively pure phloem exudate through the severed sieve tubes. Nevertheless, contamination with the contents of cells other than sieve tubes damaged at the site of incision is inevitable. For the major solutes of phloem such as sugars or amino acids that are present in high concentrations this problem is minimal but for less abundant molecules like hormones or other signals, particularly proteins or nucleic acids, conclusions about the origin and functions of these must be made with caution. The ‘natural hemophiliacs’ of the plant world are few and include a number of cucurbits, some brassicas, castor bean, species of the genus Yucca and some species of lupin (Lupinus albus, L. angustifolius, L. mutabilis and L. cosentinii). The excision technique has been expanded to plant species that do not readily exude, by chemically inhibiting the sealing mechanism. Callose production is blocked when wounded surfaces are exposed to the chelating agent ethylenediaminetetraacetic acid (EDTA) by complexing with calcium, a cofactor for callose synthase. Immersing whole, excised organs in EDTA solution, which is essential to inhibit blockage, risks contaminating sap with solutes lost from the apoplast as well as non-conducting cells. This is not an ideal technique.

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To test our hypothesis with transgenic plants, the genomic DNA fragment containing the protein-coding region and its 5′ upstream (2 to 2.5 kbp in length) and 3′ downstream regions (~500 bp) of bvORF18, bvORF19, bvORF20, or bvORF21 were separately inserted into binary vectors. The resultant constructs were named pBVORF18, pBVORF19, pBVORF20, and pBVORF21, respectively. These constructs were subsequently introduced into NK–219mm–CMS calli by Agrobacterium-mediated transformation. The calli resistant to bialaphos herbicide, a phenotype conferred by the selectable marker on the T-DNA, were transferred to a regeneration medium. The regenerated sugar beet plants contained the bialaphos-resistance gene as shown by PCR analysis using primers BAR5 and BAR6 (data not shown).

Preliminary analysis of the cauliflower mitochondrial ..

Proteomic and transcriptomic analyses have demonstrated a widely diverse composition of proteins, peptides and nucleic acids, including mRNA and small RNAs, in phloem exudates. While the origin of each individual protein or nucleic acid remains to be verified the limited compositional data available from stylectomy confirms that indeed each group of macromolecules is present in phloem. In cucurbit phloem exudate some 1110 different proteins have been detected along with a large number of mRNAs and similar data have been obtained for exudates from other species (Brassica napus, Ricinus communis and Lupinus albus). Compositional data for phloem proteins of these species show a common complement that includes phloem-specific P proteins together with proteins involved in sugar metabolism and transport, protein turnover and transport, detoxification of reactive oxygen species, as well as proteins that provide defence against insect herbivores and pathogens (Figure 10). Some undoubtedly play a role in maintenance of the SE system while others, such as the Flowering Locus T (FT) protein associated with the flowering response (‘florigen’), appear to be systemic ‘signals’ (Rodriguez-Medina et al 2011) and there may be many more. Because sieve tubes are enucleate and lack ribosomes (5.2.2 a), proteins in the translocation stream are not formed in situ but are transported from sites of synthesis in the companion cells.

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