This review focuses on the first plant defense
protein class described in literature, with growth inhibition activity toward pathogens. These
peptides were named gamma-
thionins or
defensins, which are small
proteins that can be classified into four main subtypes according to their specific functions. Gamma-
thionins are small cationic
peptides with different and special abilities. They are able to inhibit digestive
enzymes or act against bacteria and/or fungi. Current research in this area focuses particularly these two last targets, being the natural crop plant defenses improved through the use of transgenic technology. Here, we will compare primary and tertiary structures of gamma-
thionins and also will analyze their similarities to
scorpion toxins and insect
defensins. This last comparison offers some hypothesis for gamma-
thionins mechanisms of action against certain pathogens. This specific area has benefited from the recent determination of many gamma-
thionin structures. Furthermore, we also summarize molecular interactions between plant gamma-
thionins and fungi receptors, which include
membrane proteins and
lipids, shedding some light over pathogen resistance. Researches on gamma-
thionins targets could help on plant genetic improvement for production of increased resistance toward pathogens. Thus, positive results recently obtained for transgenic plants and future prospects in the area are also approached. Finally, gamma-
thionins activity has also been studied for future
drug development, capable of inhibit
tumor cell growth in human beings.