General Research Fund grant (2012 – 2013) has been awarded to Dr. Yiji Xia

Defining the role of two Nudix proteins, AtNUDT6 and AtNUDT7, in modulating the defense pathway in Arabidopsis (PI: Dr. Yiji Xia)

Plants use complex mechanisms to protect themselves from pathogen attack. Both positive and negative regulators coordinate to create signaling networks that allows plants to fine-tune its defense response to the invaders encountered. Unnecessary or excessive stimulation of the defense pathway is detrimental to plant growth. However, our knowledge on the regulatory mechanism that coordinates the activation of an appropriate defense response remains fragmentary.

We and several other groups have independently identified AtNUDT7 as a negative regulator of the defense response. AtNUDT7 is one of two dozens of Nudix domain-containing proteins in Arabidopsis. We recently found that AtNUDT6, a closest homolog of AtNUDT7, acts together with AtNUDT7 to prevent unnecessary activation of the defense pathway. The nudt6 nudt7 double mutation causes strong constitutive activation of the defense pathway, resulting in severe growth retardation. However, the precise biochemical and molecular mechanism involving these Nudix proteins in mediating the defense response remain elusive.

Our recent results suggest that AtNUDT7 and AtNUDT6 modulate production of nitric oxide (NO), an important signaling molecule that activates the defense pathway. These Nudix proteins might prevent overproduction of NO by acting as inhibitors of nitrate reductase, the major known enzyme that catalyzes NO generation in plants. Using the nudt6 nudt7 mutant as a tool, we will employ biochemical, molecular, and genetic approaches to understand the defense signaling pathway mediated by these Nudix proteins and to identify additional components involved in disease resistance.