Spider mite egg extract modifies Arabidopsis response to future infestations

Transcriptional plant responses are specially under the scope on herbivore oviposition studies. However, most of the information comes from Lepidopteran models, where egg laying and feeding are separate events, and little is known regarding the plant reaction to those pests where females feed and oviposit simultaneously. The present study unveiled the oviposition-induced transcriptomic response of plants to Tetranychus urticae eggs. Transcriptional evidence indicated that the early events on the plant response to the egg extract involved ATP, Ca2+ and ROS disbalances. The main phytohormones triggered were JA and ET, with which also participated secondary metabolites, volatiles and glucosinolates as defence mechanisms. Many of the regulated genes are also involved during pathogen-defence mechanisms. Negative regulation of defence mechanisms happened at 72 h. Female fertility was significantly reduced when fed on plants pre-exposed to the eggs, while feeding increased on those plants pre-exposed for 72 h. Overall design: Three-week-old A. thaliana Columbia (Col-0) plants were treated by applying 2 µL of egg extract and 2 µL of water on controls. After 3, 24 and 72 hpt, whole rosettes were sampled simultaneously, introduced in liquid nitrogen and stored at –80°C until used for RNA extraction. Three biological replicates of treated and control tissues were collected for each time point. Each biological replicate consisted of a pool of five whole independent rosettes. Frozen material was thoroughly grinded on liquid nitrogen and total RNA was extracted by means of the RNeasy plant mini kit (Qiagen), and a DNase treatment (Qiagen) following manufacturer´s instructions.