S-adenosylmethionine synthase (BtSAMS) from Balsas teosinte confers resistance to peach aphids in Arabidopsis

The purpose of this study was to clone S-adenosylmethionine synthase (BtSAMS) from Balsas teosinte (Zea mays ssp. parviglumis) and investigate its function via heterologous expression in Arabidopsis plants. The BtSAMS coding sequence was cloned and its length is 1185 bp. The expression of BtSAMS in Z. mays ssp. parviglumis was a 12.2-fold increase after aphid infestation. Transgenic Arabidopsis plants heterologously expressing BtSAMS were generated and their morphological characters were observed. A prolonged vegetative growth period was displayed by BtSAMS-OX plants. The more and longer trichomes were observed on the upper surface of BtSAMS seedlings. The ethylene content in BtSAMS-OX plants was not significantly different compared with the untransformed controls. These BtSAMS-OX transgenic plants showed greater resistance to peach aphids compared with the untransformed control plants. Peach aphids appeared to prefer the untransformed controls in that aphids number reduced by more than 50% on BtSAMS plants compared to controls. When sprayed with the insecticide avi-imidacloprid, the number of peach aphids decreased on BtSAMS-OX plants and untransformed controls by 91.6% and 80.5%, respectively. Peach aphids also showed lower reproduction ability when forced to feed on the transgenic plants. The number of newly born nymphs on BtSAMS plants was less than 50% of that on the untransformed control. We therefore propose that BtSAMS may be a suitable candidate gene to confer resistance to peach aphids in plants.