The phloem unloading pathway remains unclear in fleshy fruits accumulating a high level of soluble sugars. A structural investigation in apple fruit (Malus domestica Borkh. cv Golden Delicious) showed that the sieve element-companion cell complex of the sepal bundles feeding the fruit flesh is symplasmically isolated over fruit development. 14 C-autoradiography indicated that the phloem of the sepal bundles was functional for unloading. Confocal laser scanning microscopy imaging of carboxyfluorescein unloading showed that the dye remained confined to the phloem strands of the sepal bundles from the basal to the apical region of the fruit. A 52-kD putative monosaccharide transporter was immunolocalized predominantly in the plasma membrane of both the sieve elements and parenchyma cells and its amount increased during fruit development. A 90-kD plasma membrane H 1 -ATPase was also localized in the plasma membrane of the sieve element-companion cell complex. Studies of [ 14 C]sorbitol unloading suggested that an energy-driven monosaccharide transporter may be functional in phloem unloading. These data provide clear evidence for an apoplasmic phloem unloading pathway in apple fruit and give information on the structural and molecular features involved in this process.The partitioning of sugars in economically important sink organs such as fruits or seeds is governed by several complex physiological processes, including photosynthetic rate, phloem loading in the source leaf, long-distance translocation in the phloem, phloem unloading in sink organs, postphloem transport, and metabolism of imported sugars in sink cells (Oparka, 1990;Patrick, 1997). It is now well accepted that phloem unloading plays a key role in the partitioning of photoassimilate (Fisher and Oparka, 1996;Patrick, 1997;Viola et al., 2001). The process of phloem unloading has been studied extensively over the last 20 years (for review, see Oparka, 1990;Patrick, 1997;Schulz, 1998) but still remains poorly understood. Elucidation of the cellular pathway of phloem unloading is central to this process, because, to a large extent, the unloading path determines the key transport events responsible for assimilate movement from the sieve elements (SEs) to the recipient sink cells (Fisher and Oparka, 1996;Patrick, 1997). A symplasmic phloem unloading pathway predominates in most sink tissues such as vegetative apices (Oparka et al., 1995;Patrick, 1997;Imlau et al., 1999), sink leaves (Roberts et al., 1997;Imlau et al., 1999;Haupt et al., 2001), and potato tubers that represent a typical terminal vegetative storage sink (Oparka and Santa Cruz, 2000;Viola et al., 2001). Symplasmic unloading is also efficient in the maternal tissues of developing seeds that represent a class of terminal reproductive storage sinks (Ellis et al., 1992;Patrick et al., 1995;Wang et al., 1995a;Patrick, 1997), although transfer of solutes to the apoplasm may occur at some point along the postphloem pathway (Patrick, 1997). In some cases, symplasmic unloading also occurs in elongating z...
For this study, we isolated Helicobacter pylori from wastewater by a series of steps beginning with immunomagnetic separation and cell culture. After Gram staining and three standard microbial tests, the 16S rRNA sequences of a total of 23 out of 37 putative H. pylori isolates were verified by PCR. Eleven H. pylori isolates were genotyped and fell into four vacA classes: those with the vacA allelic variants s1a and m1, s1b and m1, s2 and m2, or s2 and m1. Most H. pylori isolates were of the vacA s1a/m1 type, which has been shown to be associated with advanced diseases based on genotyping of H. pylori from gastric cancer patients. These results demonstrated that H. pylori survives in water and may be a potential source of H. pylori transmission, especially where water is not adequately treated.
The acid invertase ( b b b b -fructosidase, EC 3·2·1·26) was localized at subcellular level via immunogold electron microscopy in the phloem-unloading zone of developing apple fruit. The enzyme (immunogold particles) was found to reside predominantly in the cell walls of the sieve element/ companion cell (SE/CC) complex, phloem parenchyma cells and other parenchyma cells. There was almost no gold particle found in cytoplasm and vacuole. This distribution pattern remained unchanged throughout the growing season, but the enzyme numbers varied. The density of immunogold particles increased during fruit development. The immunoblotting of soluble and insoluble acid invertases provided a supporting proof for the assays of immunolocalization. The biochemical analysis showed a predominantly cell-wall-distributed activity of acid invertase that corresponds essentially with its amount distribution. The ultrastructural observations showed that there were numerous plasmodesmata between the parenchyma cells, but almost no plasmodesmium between the SE/CC complex and its surrounding parenchyma cells, practically resulting in the symplasmic isolation of the SE/CC complex. It is therefore suggested that the unloading pathway of sucrose from the SE/CC complex may be predominantly apoplasmic in the developing apple fruit, and that the unloaded sucrose may be hydrolysed by the functional acid invertase localized in the cell wall before it is loaded in sink cells.
Gutierrez et al., 2002; Lu and Myers, 2002). Genetic distances could be as low as 1 to 3%. Research in Austra-Genetic diversity in modern upland cotton cultivars (Gossypium lia, China, and Pakistan obtained similar results (Multani hirsutum L.) is thought to be narrow, thus limiting genetic advance. Robust information on the genetic relatedness among currently grown and Lyon, 1995; Zuo et al., 2000;Rahman et al., 2002). cotton cultivars is lacking. The objectives of the present study were The hypothesized narrow genetic base of upland cotto field test a sample of elite commercial cotton cultivars, including ton germplasm used in breeding has been considered many transgenic cultivars representing the major cottonseed compaas one of the reasons contributing to the lack of progress nies, and to evaluate their genetic divergence using simple sequence in the improvement of cotton cultivars to meet the needs repeat (SSR) markers. Eighty-eight SSR primer pairs were chosen of cotton growers and industry in the USA during the for genotyping that provided 177 SSRs. Jaccard's genetic similarity last 15 yr (Meredith, 2000; Lewis, 2001). A series of coefficients among 24 genotypes ranged from 0.694 to 0.936, with an studies on pedigrees, coefficients of parentage (CPs), average of 0.772, indicating that sufficient genetic diversity does exist and genetic diversity for 260 cotton cultivars released
BackgroundLilium lancifolium, a very important cold-resistant wild flower for lily cold resistance breeding, is widely distributed in southwestern and northeastern China. To gain a better understanding of the cold signaling pathway and the molecular metabolic reactions involved in the cold response, we performed a genome-wide transcriptional analysis using RNA-Seq.ResultsApproximately 104,703 million clean 90- bp paired-end reads were obtained from three libraries (CK 0 h, Cold-treated 2 h and 16 h at 4°C); 18,736 unigenes showed similarity to known proteins in the Swiss-Prot protein database, and 15,898, 13,705 and 1849 unigenes aligned to existing sequences in the KEGG and COG databases (comprising 25 COG categories) and formed 12 SOM clusters, respectively. Based on qRT-PCR results, we studied three signal regulation pathways —the Ca2+ and ABA independent/dependent pathways —that conduct cold signals to signal transduction genes such as LlICE and LlCDPK and transcription factor genes such as LlDREB1/CBF, LlAP2/EREBP, LlNAC1, LlR2R3-MYB and LlBZIP, which were expressed highly in bulb. LlFAD3, Llβ-amylase, LlP5CS and LlCLS responded to cold and enhanced adaptation processes that involve changes in the expression of transcripts related to cellular osmoprotectants and carbohydrate metabolism during cold stress.ConclusionsOur study of differentially expressed genes involved in cold-related metabolic pathways and transcription factors facilitated the discovery of cold-resistance genes and the cold signal transcriptional networks, and identified potential key components in the regulation of the cold response in L lancifolium, which will be most beneficial for further research and in-depth exploration of cold-resistance breeding candidate genes in lily.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-203) contains supplementary material, which is available to authorized users.
ods. In Tennessee, genetic gain in yield improvement was 7.2 kg ha Ϫ1 yr Ϫ1 as calculated by Culp and GreenThe New Mexico cotton breeding program was established in 1926 (1992) on the basis of the data from Hoskinson and Stewand has been led by five generations of breeders and geneticists. The program has released more than 30 Acala 1517 cotton (Gossypium hir- art (1977). In South Carolina, genetic gain in yield imsutum L.) cultivars and numerous germplasm lines known for high fiber provements was 10.5 kg ha Ϫ1 yr Ϫ1 for commercial cultiquality and Verticillium wilt (caused by Verticillium dahliae Kleb.) tolvars and 15.1 kg ha Ϫ1 yr Ϫ1 for Pee Dee germplasm lines erance that have made substantial contributions to cotton breeding in from 1945 to 1978 (Culp and Green, 1992). For Califorthe USA. The present project was initiated in 2003 to evaluate the genia Acala cotton, Bassett and Hyer (1985) estimated netic improvement of Acala 1517 cultivars and lines released over the the genetic gain of 8.0 kg ha Ϫ1 yr Ϫ1 from 1930 to 1980. past 75 yr in yield, boll size, seed index, lint percentage, fiber length, fiber In the Mississippi Delta, genetic gain in lint yield imstrength, and micronaire. Their genetic divergence was also estimated by provements averaged 9.1 to 10.2 kg ha Ϫ1 yr Ϫ1 from 1922 simple sequence repeat (SSR) markers. On the basis of the data availto 1966 and 8.5 to 9.5 kg ha Ϫ1 yr Ϫ1 from 1910 to 1978; able from annual yield trials, lint yield and lint percentage in Acala however, the rate was shown to be decreased when a 1517 cotton have steadily increased since the 1930s, while boll size and seed index have gradually decreased since the 1960s. Fiber strength has longer period was included in the analysis: 5.4 kg ha Ϫ1 been enhanced since the 1960s, which has been accompanied by steady yr Ϫ1 from 1938 to 1993 and 4.7 kg ha Ϫ1 yr Ϫ1 from 1938 to increase in micronaire. However, fiber length in Acala 1517 cultivars 1999. The genetic gain was further decreased to 3.5 kg tended to shorten from 31.0 to 30.0 mm from 1960 to 1990, whereas ha Ϫ1 yr Ϫ1 from 1983 to 1999 (Bridge et al., 1971; Bridge newly released Acala 1517 cultivars (Acala 1517-95, 1517-99, 1517-02, and Meredith, 1983; Meredith 2000). The slowed ge-1517-03, and 1517-04) have fiber greater than 30.5 mm. Genetic distance netic gain in cotton yield improvement was thought to among Acala 1517 genotypes ranged from 0.06 to 0.38 with an average be due to narrow genetic base of upland cotton and of 0.18 on the basis of 189 SSR marker alleles, indicating a substantial repeated use of a few upland cotton germplasm in major genetic diversity among Acala 1517 cotton germplasm. Divergent germcommercial cotton breeding programs (May et al., 1995; plasm introgression in the program has contributed to genetic diver-Meredith, 2000; Lewis, 2001). sity of Acala cotton germplasm and continuous genetic gain in Acala cotton cultivar improvement.
Degenerate primers designed from conserved motifs of known plant resistance gene products were used to amplify genomic DNA sequences from the root-knot nematode (Meloidogyne incognita) resistance genetic source, Upland cotton (Gossypium hirsutum) cultivar Auburn 634 RNR. A total of 165 clones were isolated, and sequence analysis revealed 57 of the clones to be novel nucleotide sequences, many containing the resistance (R)-protein nucleotide-binding site motif. A cluster analysis was performed with resistance gene analogue (RGA) nucleotide sequences isolated in this study, in addition to 99 cotton RGA nucleotide sequences already deposited in GenBank, to generate a phylogenetic tree of cotton R genes. The cotton RGA nucleotide sequences were arranged into 11 groups and 56 sub-groups, based on genetic distances. Multiple sequence alignments were performed on the RGA sequences of each sub-group, and either the consensus sequences or individual RGA sequences were used to design 61 RGA-sequence-tagged site primers. A recombinant inbred line (RIL) population of cultivated tetraploid cotton was genotyped using RGA-specific primers that amplified polymorphic fragments between the two RIL parents. Nine RGA markers were mapped to homeologous chromosomes 12 and 26, based on linkage to existing markers that are located on these chromosomes.
Plants have continually confrontation with different abiotic stresses, including salt, low temperature, drought or hormone stress. The plants acclimate to the environmental stresses relating with the falls of the molecular mesh including the stress signal receiver, signal transcriptional regulation and the expression of functional and structure genes. Using the RNA-seq, we carried out a transcriptional analysis under cold treatment for investigating a profound comprehension of the signal network and molecular metabolisms reaction included in abiotic stress reaction for Lilium lancifolium. Our study identified 18,722 unigenes had demonstrated the resemblance to the known exact proteins in the Swiss-Prot protein database and classified them by Gene ontology into three primary kinds: cellular component, biological process, and molecular function, and then 15,898 unigenes aligned to existing sequences in the KEGG databases. Based on the transcriptome results of cold stress, more stress-related genes were identified and analyzed of their expressions in other abiotic stress treatments as 37 °C, ABA, JA and Na. Meanwhile, bioinformatics qRT-PCR analyses of stress genes as LlDREB1, LlAP2, LlNAC1, LlHOT, LlR2R3-MYB and LlCDPK revealed that novel candidate genes encoding ethylene responsive transporters and serine/threonine receptor-like kinases, which contributed to speculate the signal regulation pathway during the abiotic stresses; engineering genes could also boost the tolerance to stress, as protected and maintained the function and structure of cellular components. Our research conjectured the abiotic stress signal transduction pathway and identified the expected key ingredients regulating the stress tolerance in Lilium lancifolium, which would enable the in-depth molecular exploration of stress-tolerance mechanisms in lily.
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