Perturbing the metabolic dynamics of myo-inositol in developing Brassica napus seeds through in vivo methylation impacts its utilization as phytate precursor and affects downstream metabolic pathways.

BACKGROUND: myo-Inositol (Ins) metabolism during early stages of seed development plays an important role in determining the distributional relationships of some seed storage components such as the antinutritional factors, sucrose galactosides (also known as raffinose oligosaccharides) and phytic acid (PhA) (myo-inositol 1,2,3,4,5,6-hexakisphosphate). The former is a group of oligosaccharides, which plays a role in desiccation at seed maturation. They are not easily digested by monogastric animals, hence their flatulence-causing properties. Phytic acid is highly negatively charged, which chelates positive ions of essential minerals and decreases their bioavailability. It is also a major cause of phosphate-related water pollution. Our aim was to investigate the influence of competitive diversion of Ins as common substrate on the biosynthesis of phytate and sucrose galactosides. RESULTS: We have studied the initial metabolic patterns of Ins in developing seeds of Brassica napus and determined that early stages of seed development are marked by rapid deployment of Ins into a variety of pathways, dominated by interconversion of polar (Ins phosphates) and non-polar (phospholipids) species. In a time course experiment at early stages of seed development, we show Ins to be a highly significant constituent of the endosperm and seed coat, but with no phytate biosynthesis occurring in either tissue. Phytate accumulation appears to be confined mainly within the embryo throughout seed development and maturation. In our approach, the gene for myo-inositol methyltransferase (IMT), isolated from Mesembryanthemum crystallinum (ice plant), was transferred to B. napus under the control of the seed-specific promoters, napin and phaseolin. Introduction of this new metabolic step during seed development prompted Ins conversion to the corresponding monomethyl ether, ononitol, and affected phytate accumulation. We were able to produce homozygous transgenic lines with 19%-35% average phytate reduction. Additionally, changes in the raffinose content and related sugars occurred along with enhanced sucrose levels. Germination rates, viability and other seed parameters were unaffected by the IMT transgene over-expression. CONCLUSIONS: Competitive methylation of Ins during seed development reduces seed antinutritional components and enhances its nutritional characteristics while maintaining adequate phosphate reserves. Such approach should potentially raise the canola market value and likely, that of other crops.

Gene expression at early stages of Brassica napus seed development as revealed by transcript profiling of seed-abundant cDNAs.

Approximately 5000 plaques derived from a Brassica napus L. (canola) seed-cDNA library representing 15 days after pollination (DAP) were differentially screened for highly expressed genes at the early stages of seed development. Analysis of 104 differentially expressed sequence tags revealed 54 unique genes, of which 33 had putative homologues described in Arabidopsis thaliana (L.) Heynh. or B. napus. These encoded diverse proteins, ranging from proteins of unknown function to metabolic enzymes and proteins associated with cell structure and development. Twenty-five genes were only expressed in seeds, and 11 of these started to express as early as 5 or 10 DAP. The majority of the seed-specific genes that are expressed at early stages of seed development encoded proteins with high similarity to hypothetical Arabidopsis proteins. Tissue-specificity determined by Northern analysis revealed that four seed-specific genes were expressed only in seed coats and another five in both embryos and seed coats. Analysis of transcript profiles of seed-abundant as well as seed-specific genes, and their expression patterns, implies that the B. napus seed is undergoing an active cell proliferation during 10-20 DAP, while establishing metabolic networks for subsequent seed maturation.

[Preparation of rabbit anti-Syk antibody and its application in breast cancer diagnosis].

AIM: To prepare rabbit anti-Syk antibody and analysis its application in breast cancer diagnosis. METHODS: The rabbits were immunized with recombinant mouse Syk protein to prepare antibody against Syk. The purity and specificity of the antibody were analyzed by Western blot. The expression of Syk protein was detected by immunohistochemical staining. RESULTS: The titer of serum anti-Syk antibody was 1:6 400 (A450 = 1. 03) 6 weeks after the immunization. The SDS-PAGE and Western blot analysis showed that there was a obvious protein band with Mr 72,000, confirming the specificity of obtained anti-Syk antibody. It was displayed by immunohistochemical staining with anti-Sykantibody that in normal breast tissue Syk was high expression; while in infilfrative dustal carcinoma of breast tissue the expression of syk was negative. CONCLUSION: The rabbit anti-Syk antibody with high titer and specificity has been prepared. The Syk is high expression in normal breast tissue, but is deficient in breast cancer tissue. The result may be useful for clinical diagnosis of breast cancer.

[Extraction and purification of non-receptor type PTKs-Syk].

AIM: To extract and purify Syk protein from Sf21 cells transfected by Syk gene. METHODS: Sf21 cells were transfected with recombinant syk gene. After 48 h of incubation at 28 degrees Celsius, the transfected cells were collected and sonicated with Sonfier sonicator on ice. Filtered cell extract was loaded onto a Reactive Yellow-3 resin column and Toyopearl AF-Heparin-650 M column respectively. The characters of Syk protein in the fractions were identified by SDS-PAGE, Western blotting and IEF. RESULTS: 225 mg of protein containing Syk were obtained from Sf21 cells (2.5 x 10(9))extract. There were two subpopulations in the elution of Reactive Yellow-3 resin column with the same relative molecular mass (Mr) 72 x 10(3). The two subpopulations were then applied on Toyopearl AF-Heparin-650 M column and two pure proteins were obtained. The results of SDS-PAGE, Western blotting, and IEF showed the two proteins having the same relative molecular mass (72 x 10(3)), corresponding to Syk, but with different pI. CONCLUSION: The yield of Syk was 8 mg from 2.5 billion cells and the purity was > 95%. The two purified Syk proteins have the same Mr and different pI. The purified Syk protein can be applied to study Syk's mechanism, produce anti-Syk antibody and invent Syk diagnosis kit, etc.