Recode the treatment variable (in the genexpr dataset) so you have the levels control, A, B and AB.

 

   replicate      id treatment    Gene1    Gene2    Gene3    Gene4    Gene5    Gene6    Gene7   ...
1          1 ID 9239   Control 29.60523 20.84956 27.11910 19.30535 18.37085 18.35265 22.95577
2          2 ID 9239   Control 20.39603 24.55238 19.88842 20.21842 19.94912 32.39009 25.84113
3          3 ID 9239   Control 24.94694 20.98351 21.90802 14.96396 31.19226 31.77084 18.06114
4          4 ID 9239   Control 24.96139 26.71594 17.64886 18.79438 20.76621 25.87369 22.74943
5          5 ID 9239   Control 22.28186 19.15017 25.28507 14.05407 24.59658 27.22024 20.01675
6          1 ID 7057   Control 24.59369 22.23258 18.49725 10.12569 20.10379 17.09188 17.45587
7          2 ID 7057   Control 26.17200 21.02197 23.42640 16.01828 14.09717 16.30789 27.77393
8          3 ID 7057   Control 23.38154 24.85749 29.31398 15.06018 20.64261 15.16328 22.61038
9          4 ID 7057   Control 18.89204 16.88536 24.14300 12.35423 15.68445 23.80580 38.25066
10         5 ID 7057   Control 15.35030 18.42504 27.78034 10.71458 20.86934 25.98996 27.03204