Plants do not have an immune system like animals do to fend of pathogenes. Recently Xinnian Dong discovered how plants mobilize defenses. At Howard Hughes Medical Institute they found several candidates that belong to a family of proteins that help plants survive high temperatures. Plants can switch on genes that code pathogene- fighting proteins. The on-off switches for these genes often carry a characteristic gene sequence called TL1.
See her research paper on Mechanisms and Dynamic Regulation of Plant Immune Responses.