[Cloning and sequence analysis of MYB transcriptional regulator SmP gene of Saussurea medusa Maxim].

A full-length cDNA encoding a MYB-related regulatory gene was isolated from a cDNA library prepared from mRNAs of the red line callus of S. medusa by TD-PCR. The cDNA, designated SmP, is 969 nucleotides long and has an open reading frame of 771 bp with a deduced amino acid sequence of 256 residues. The putative protein of SmP has two typical conversed R2R3-Myb DNA-binding domains in N-terminal and displays a rather high degree of similarity to OsMYB from rice and LBMI from tobacco, showing 73% and 70% identity within the DNA-binding domains. However, the C-terminal domain of the SmP protein does not show obvious similarity to any other known protein sequence. It is rich in hydrophilic amino acids, especially in serine residues (18.38%), partly organized in homopolymeric stretches, a feature often found in activation domain of transcription factors.

[SSS method for screening cDNA library].

A quick and simple method subsection screening (SSS) method for screening cDNA library by PCR was established. With this method, cDNA phage plate was cut into several blocks and a couple of primers was designed according to target gene. And then the target genes were obtained by screening cDNA library. Comparing with other methods,this method has many advantages such as controlled range and clear target,and also quick and simple for obtaining the target genes. It is possible to get a target gene in one week in general by this method. Thus,the CHI gene, F3'H gene, HSP gene and one HSP partial fragment, were obtained respectively in half month in our lab. We can get twice the result with half the effort when we screen several genes in the same time. It is also suitable to screen other libraries.