Systemin: A Wound Responsive Plant Peptide Hormone

Systemin released from the wounded places of tomato leaves caused by insect herbivore or other mechanical damage. Systemin is formed from the larger precursor protein known as prosystemin. In the leaves of unwounded plants, prosystemin is found in the less amount and increases many folds more in response to wounding. Prosystemin amplify the wound signal when the plant is under attack. The processing of prosystemin takes place as a result of wounding, which is thought to mix prosystemin with proteolytic enzymes from another cellular compartment, resulting in the release of systemin. Systemin regulates the activation of defensive genes against the herbivore and pathogen attacks in tomato plants. It is capable of moving in the plants and to induce genes encoding defense proteins leading to immunological response. The characteristics of systemin indicate that it is a systemic wound hormone that plays an important role in the regulation of the expression of defense genes in response to pathogen attacks.