Biologists Discover an On/Off Button on Plants' Alarm System

Plants have inherent defense keys that would turn on/off like switch buttons when they are confronted with pathogen and herbivore attack. Early studies showed that the hormone jasmonate is crucial in this process as a signaling molecule, but is not known how, until a group of researchers of the University of Ghent and Vrije Universiteit Brussel (VIB) unveiled a new protein involved in the defense activation pathway.

During herbivore or pathogen attack, the jasmonates sets a cascade of events that start with the degradation of JAZ proteins that frees up protein MYC2, the signal for launching the genetic defense programs and stops the plant's growth. Using the proteomics-based technology developed by Geert De Jaeger (VIB/Ghent University) and Erwin Witters (VITO/University of Antwerp), NINJA or Novel INteractor of JAZ protein was found to block the MYC2 proteins' activity. It does so by connecting the JAZ with another protein TPL – an auxin regulated protein. The report published in Nature revealed that the complex of these proteins (JAZ-NINJA-TPL) bind to MYC2 to make it remain inactive. On the other hand during times of stress, the JAZ proteins disappear and MYC2 triggers the plant's defense mechanism.

The results bring insights on how stress- and growth-related signaling pathways use the same molecular mechanisms to regulate gene expression in plants. The study could also be a spring board to the development of secondary metabolites in stressed plants which can have practical applications in the field of pharma and nutraceuticals.

For details, see the story at http://www.vib.be/NR/rdonlyres/02CE3C9E-C278-486C-981F-4D5742148427/3049/20100401_ENG_Goossens_Ninja_web.pdf.