Setup of split-root experiments. Seeds of soybean wild-type, nts382, and nts1007 were germinated for 6 days. After cutting off the main root followed by 2 days of recovery, plants were transferred to the split-root system by dividing lateral roots on two pots. In doing so, one root-part of mycorrhizal plants ('treatment') was inoculated with R. irregularis (indicated by the dark color); the other root-part stayed non-infected. Control plants remained non-inoculated on both sides. Nineteen days after initial inoculation, part of the plants was harvested for transcript profiling and RT-qPCR analysis (1. harvest). Remaining plants were transferred to bigger pots to inoculate them with R. irregularis at another root-part to check for the AOM effect after another 21 days. In addition, in split-root experiments II and III, some of the initially inoculated plants were, without any subsequent inoculation, harvested at approximately 6 weeks after inoculation for further gene expression analysis (not shown). For pictures of plants see Figure S1 in Additional file 1.
Schaarschmidt et al. Genome Biology 2013 14:R62 doi:10.1186/gb-2013-14-6-r62