[Analysis of genomic DNA methylation level in radish under cadmium stress by methylation-sensitive amplified polymorphism technique].

The level of cytosine methylation induced by cadmium in radish (Raphanus sativus L.) genome was analysed using the technique of methylation-sensitive amplified polymorphism (MSAP). The MSAP ratios in radish seedling exposed to cadmium chloride at the concentration of 50, 250 and 500 mg/L were 37%, 43% and 51%, respectively, and the control was 34%; the full methylation levels (C(m)CGG in double strands) were at 23%, 25% and 27%, respectively, while the control was 22%. The level of increase in MSAP and full methylation indicated that de novo methylation occurred in some 5'-CCGG sites under Cd stress. There was significant positive correlation between increase of total DNA methylation level and CdCl(2) concentration. Four types of MSAP patterns: de novo methylation, de-methylation, atypical pattern and no changes of methylation pattern were identified among CdCl(2) treatments and the control. DNA methylation alteration in plants treated with CdCl(2) was mainly through de novo methylation.

[Novel molecular marker systems--SRAP and TRAP and their application].

SRAP and TRAP are two kinds of newly developed molecular marker systems with the advantages of simplicity, high throughput, numerous co-dominant makers, highly reproducibility and ready to sequence, especially preferential targeting ORFs. The principle and protocol of SRAP and TRAP, which were developed in Brassica and Helianthus crops firstly, are introduced in the paper. Primer design is a key step for SRAP and TRAP, and some F-and R-primers were developed. Unlike SRAP technique, the TRAP requires cDNA or EST sequence information for fixed primer development. The annealing temperature is 35 degrees in the first 5 cycles and 50 degrees in the subsequent 30~35 cycles. The amplicons can be separated by polyacrylamide or agarose gel, and detected by autoradiography, silver or EB staining. SRAP and TRAP are applied in germplasm genetic diversity analysis, genetic map including transcriptome map construction, important trait gene tagging and gene cloning in many crops.