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The aims of this study were to isolate and characterize putative fragrance-related cDNAs from the floral cDNA library of Vanda Mimi Palmer, an orchid hybrid that has won several international awards for its sweet fragrance. A total of 1,000,000 pfu were screened by hybridizing cDNA library plaques with fully open flower cDNA probe of Vanda Mimi Palmer representing all mRNAs expressed during daytime. The clones that gave positive signals were in vivo excised and PCR-amplified inserts were subjected to reverse-Northern analysis by hybridizing with cDNA probes of fully open flower of Vanda Mimi Palmer (fragrant orchid) and its bud or fully open flower of Vanda Tan Chay Yan (non-fragrant orchid) separately. The clones up-regulated in fully open flower stage of Vanda Mimi Palmer compared to its bud stage or fully open flower of Vanda Tan Chay Yan were sequenced. Sequence analyses showed the presence of eight putative fragrance-related cDNAs of which two were putative Vanda Mimi Palmer 4-(cytidine 5'-diphospho)-2-Cmethyl-D-erythritol kinase (VMPCMEK) and Vanda Mimi Palmer cytochrome P450 protein (VMPCyP450). These two transcripts were selected for full-length cDNA isolation and expression analysis by real-time RT-PCR. The VMPCMEK transcript encodes a polypeptide of 400 amino acid residues, while the VMPCyP450 encodes 538 amino acid residues. Relative expression analysis of VMPCMEK and VMPCyP450 transcripts by real-time RT-PCR showed up-regulated expressions in floral tissues compared to vegetative tissues, and both were found to be developmentally regulated.
Grain filling is an important agronomic trait, which directly affects the final yield of rice. Partially filled and empty rice grains are among the factors that limit the yield of MR219, one of the highest yielding rice varieties in Malaysia. In this study, the NSF 20 K rice oligonucleotide array, which contains 20,000 70-mer oligonucleotide probes, was used for direct comparison of the transcriptomes of MR219 and MR84 (a rice variety that has higher percentage of filled grains compared to MR219), during rapid grain-filling period at 5 and 10 days after fertilization (DAF). A total of 155 and 233 genes were differentially expressed in MR219 compared to MR84 at 5 and 10 DAF, respectively; and 9 of these expression ratios were tested using quantitative real-time RT PCR. Among the differentially expressed genes identified were those encoding hexokinase, various sugar transporters, GSDL-like lipase/ acylhydrolase, brassinosteroid-insensitive 1-associated receptor kinase 1 precursor and homeobox protein GLABRA2, which were analyzed by real-time RT PCR in this study. The differences demonstrated by these genes in their transcript levels and profiles, between the two rice varieties understudied at different stages of grain filling may contribute to the formulation of hypotheses toward the understanding of poor percentage of filled grains in MR219.
A comparative phenotypic and morpho-histological study was carried out on tissue culture-derived truncated leaf syndrome (TLS) and wild-type oil palm seedlings to investigate their phenotypic and morpho-histological differences. On the basis of the percentage of TLS occurence in a clone, the TLS seedlings were categorized into three groups: severe (70–100%), moderate (40–69%) and mild (\40%). Wild and TLS seedlings differ in terms of growth, vigor, leaf size and shape, root number, volume, length as well as the size of shoot apical meristem (SAM). Differences were also found in fresh weight of leaf, root and SAM of TLS in comparison to wild-type seedlings. Depressed and wavy leaf surface, sunken and distorted stomata and coalesced epidermal cells were observed by scanning electron microscopy in TLS seedlings. The size, shape and number of stomata were also different in the TLS leaf compared to the wild type. Longer epidermal cells, depressed epidermal layer, larger sub-epidermal cells and loosely arranged less mesophyll cells were observed in TLS leaf than in wild type. Undifferentiated vascular bundle was found in TLS leaves where metaxylem and phloem were absent and root tips were impaired. The size and leaf primordial arrangement of SAM were remarkably different in TLS compared to wild-type seedlings suggesting that these alterations might be due to smaller SAM. Therefore, further detailed genetic analysis on TLS SAM is needed for clear understanding of TLS occurrence.
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