The Role of Salicylic Acid, Jasmonic Acid and Ethylene in Plant Defense

Abstract— A complex network of cross – talk between the salicylic acid (SA) and jasmonic acid (JA) pathways further fine tunes plant defense responses. SA can be formed from cinnamate via o – coumarate or benzoate depending on whether the hydroxylation of the aromatic ring takes place before or after the chain – shortening reactions. SA not only functions against biotrophs, but also activates plant resistance against the below – ground disease such as root – knot nematodes. The synthesis of jasmonates and many other oxylipins is initiated by lipoxygenases (LOXs), which catalyze the regio – and stereoselective dioxygenation of polyunsaturated fatty acids. JA activates plant immune responses to necrotrophic pathogens, some phloem – feeding insects and chewing herbivores. Also JA is also involved in other aspects of plant – pathogen interactions, including systemic acquired resistance (SAR). The role of ethylene (ET) in plant diseases resistance is dramatically different duo to type of pathogene and plant species. There are many evidence that show ethylene response is linked to gene for gene resistance. It is proven that there are a strong connection between different pathways related to SA, JA and ET for plant diseases resistance. So that SA – dependent and JA/ethylene – dependent pathwa ys induce expression of different sets of PR genes and result in plant resistance to different pathogens.