Hence, linking resistance genes with resistance phenotypes will be more and more important for the understanding of why some isolates are extremely resistant and why some contain multiple resistance genes encoding resistance to the same antimicrobial classes.
Several BPH resistant introgression lines (ILs), near-isogenic lines (NILs) and pyramided lines (PLs) carrying single or multiple resistance genes were developed by marker assisted backcross breeding (MABC).
Multiple resistance genes travel on the same mobile genetic element (e.g., plasmid), allowing one pharmaceutical to select for microorganisms that are resistant to multiple classes of antibiotics (Wright 2007).
It is also becoming increasingly common to find multiple resistance genes that are linked together, thus antibiotics from unrelated classes may contribute to the selective pressures and maintain the expression of these multidrug resistant genes [ 3, 4].
Moreover, SOX4 overexpression upregulated multiple drug resistant gene ABCG2, and SOX4 downregulation inhibited ABCG2 expression.
SOX4 regulation also affected drug sensitivity via modulation of multiple drug resistant gene AGCG2, suggesting that SOX4 may be an indicator for clinical drug selection and CC chemotherapy.
These cells usually express high levels of multiple drug resistant gene (MDR1) [ 8] and ATP binding cassette (ABC) transporter [ 9] and are therefore resistant to chemotherapy and considered as the major source of drug-resistance in tumors.
These plasmids can carry multiple drug-resistant genes against aminoglycosides, quinolones and sulfamethoxazole at the same time.
Seriously, most of them usually co-harbor other resistant genes mediating resistance to multiple classes of antibiotics such as fluoroquinolones or aminoglycosides [ 3], which leads to MDR events.
However, the previous studies were performed using different mapping populations, different markers, as well as different biotypes, which make it difficult to determine if a single resistance gene has multiple alleles or if several resistant genes reside on the short arm of chromosome 1A.
