The effect of temperature on Agrobacterium tumefaciens-mediated gene transfer to plants

Agrobacterium tumefaciens is generally used to achieve genetic transformation of plants. The temperatures that have been used for infection with Agrobacterium in published transformation protocols differ widely and, to our knowledge, the effect of temperature on the efficiency of T-DNA transfer to plants has not been investigated systematically. Agrobacterium tumefaciens strains harbouring a binary vector with the beta-glucuronidase (uidA) gene and either a nopaline-, an octopine- or an agropine/succinamopine-type helper plasmid were tested in two transformation systems at temperatures between 15 and 29 degrees C. One system involved cocultivation of Phaseolus acutifolius callus whereas in the other system Nicotiana tabacum leaves were vacuum-infiltrated. In both situations, irrespective of the type of helper plasmid, the levels of transient uidA expression decreased notably when the temperature was raised above 22 degrees C. Expression was low at 27 degrees C and undetectable at 29 degrees C. We anticipate that the efficiency of many published transformation protocols can be improved by reconsidering the factor of temperature.