3. Results and discussion
3.1. Isolation of differentially expressed genes in L. regale after F. oxysporum inoculation by SSH
To enrich the differentially expressed genes in resistant defense response of L. regale, a subtracted cDNA library of L.
regale inoculated with F. oxysporum was constructed. The cDNA transcribed from the mRNA of F. oxysporum infected
root was as the tester, and the cDNA from mock-inoculated root as the driver. Two rounds of subtraction between the tester
and the driver were performed, then the pool of differentially expressed gene fragments was amplified with primers of 1 and
2R. Through TA-cloning and blue-white spot screening, 3168 clones were randomly picked.
Totally, 1726 clones were screened out by colony PCR, and the length of cDNA inserts ranged from 200 to 1000 bp with
average length of 400 bp. Then 1101 clones were successfully sequenced, and there were 585 unique sequences including
194 contigs and 391 singlets through CAP3 sequence analysis.
3.2. Functional categories of genes responsive to F. oxysporum infection
The 585 unique sequences were then performed homology analysis with BLASTx tool in GenBank. As a result, more
than one half of the unique sequences were assigned to no significant homology. The partial result of homology analysis
was showed in Table 1. The functional categories of the 243 ESTs which had significant homology with known proteins
were assigned, as a result, they were classified into 14 putative cellular functions on the base of categories established in
Arabidopsis (Fig 1).