Significant progress which was made during last few years in research of jasmonic acid signaling pathway yielded surprising information about chemical form of a signaling molecule of the hormone, which turned out to be its conjugate with amino acid isoleucine. Function of jasmonic acid receptor is more and more frequently attributed to COI1 protein which is structurally and functionally similar to the auxin receptor TIR1. Signal perception takes place in the nucleus and leads to the activation of SCF(COI1) ubiquitine ligase and consequently to proteolysis of transcription repressors, the JAZ proteins. Reduced pool of these negative regulators enables to activate the transcription factors (i. e. ERF1, WRKY70, MYC2), as well as expression of genes involved in defense responses of plants (i. e. PDF1.2, VSP1, CHI-B). Jasmonic acid signal transduction pathway, is also subjected to complicated regulations, including both positive, and negative feedbacks, which enable plants react adequately to variable environmental conditions.