| Soil salinization is a very serious agriculture problem.Most of crops are lower tolerant to salt stress.Therefore, the object in plant breeding is to breed crop varieties with relatively high salt tolerance.Isolation and identification of salt tolerant genes play an important role in salt-tolerant breeding.The salt tolerance of plant is a quantitative genetic trait regulated by plenty of genes. In resent years, much of structural genetic products,such as transport proteins,ion channel proteins,solute synthesis related enzymes,and the regulating effect of these products were regarded.Because of the huge plant genome,it is difficult to find out the target genes under the unclear genetic background.However, with the rapid development of biochemistry, enzymology,molecular biology,the target genes were isolated in effective ways.mRNA differential display reverse transcription polymerase chain reaction (DDRT-PCR) technique is very conspicuous.The establishment of mRNA differential display tachnique makes it possible for studying the differential expression of salt tolerant genes in different tissues,organs,environmental condition and beedtime. It also provides many valuable experimental results for the studying of molecularmechanism of plant salt tolerance.Now, this technique has been widely applied to study molecular mechanism of resistant genes ,such as drought tolerance,cold endurance and disease resistance.This study used young leaves of wheat ( Baofeng 7228r) seedings as materials. With the DDRT-PCR technique ,the gene expression differentiation of leaves in the normal condition and in the salt stress condition were analysed. In order to find out valuable salt tolerant related genes,mRNA was isolated and purified from leaves of seedlings treated with 1.0% NaCl for 72 hours.The first chain of cDNA was synthesized via reverse transcription with anchor primer Oligo(dT)12GC. PCR amplification was carried out with 10bp random primers for two times.and the re-amplified products were separated in 2.0% agarose gel. 27 differential cDNA fragments,including 12 inductive expression fragments, 4 intensive expression fragments and 11 inhibitory expression fragments were detected. 11 cDNA fragments with obvious difference were cloned. The result of Northern Blotting showed that SR01,SR03,SR07 fragments had obvious salt inductive expression characteristics, the wheat which was treated by NaCl had signal of hybridization,whereas the control had no signal.And then, sequence analyses and homologous comparisons of SR01.SR03.SR07 were carried out.Analysis through GenBank/BLAST database revealed that SR01 has no identity to known genes or proteins,suggesting that it is unknown protein.The homology of nucleotide sequence between SR03 and actin is up to 33%.Actin is a kind of important proteins existing universally in eukaryotes, which constitutes the microfibril system in cytoskelet. Actin and myosin play significant role in the movement of cytoplasm. It is suggested that the coding product of SR03 makes wheat cells defend against salt stress by participating in the movement of cytoplasm.The homology of protein sequence between SR07 fragment and water channel proteins (PIPs) is 87%. It is speculated that the coding product of SR07 is a kind of water channel proteins or their analog.The expression of SR07 in the wheat is a kind of actively reaction to adapt to salt stress.In addition,the biological information analysis of SR07 fragment indicates thatthis gene segment has a 561bp open read frame (ORF),which codes 186 amino acid residues,with initiation codon at site of 55 nucleotide acid and termination codon at site of 613 nucleotide acid.There are 54 non-coding nucleotide sequence at 5' end and 165 non-coding nucleotide sequence at 3' end.The molecular weight of protein encoded by SR07 is around 19639.65 and the isoelectric point of the protein is 7.745.The transmembrane analysis indicates that this protein has two membrane-spanning regions:at sites of 10-15 and 25-35 amino acids respectively.Moreover,the phosphoryl...
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