AUTHOR=Ma Lisong , Cornelissen Ben J., Takken Frank L.

TITLE=A nuclear localization for Avr2 from Fusarium oxysporum is required to activate the tomato resistance protein I-2

JOURNAL=Frontiers in Plant Science

VOLUME=4

YEAR=2013

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2013.00094

DOI=10.3389/fpls.2013.00094

ISSN=1664-462X

ABSTRACT=<p>Plant pathogens secrete effector proteins to promote host colonization. During infection of tomato xylem vessels, <italic>Fusarium oxysporum</italic> f. sp. <italic>lycopersici</italic> (<italic>Fol</italic>) secretes the Avr2 effector protein. Besides being a virulence factor, Avr2 is recognized intracellularly by the tomato I-2 resistance protein, resulting in the induction of host defenses. Here, we show that <italic>AVR2</italic> is highly expressed in root- and xylem-colonizing hyphae three days post inoculation of roots. Co-expression of <italic>I-2</italic> with <italic>AVR2</italic> deletion constructs using agroinfiltration in <italic>Nicotiana benthamiana</italic> leaves revealed that, except for the N-terminal 17 amino acids, the entire <italic>AVR2</italic> protein is required to trigger <italic>I-2</italic>-mediated cell death. The truncated Avr2 variants are still able to form homo-dimers, showing that the central region of Avr2 is required for dimerization. Simultaneous production of I-2 and Avr2 chimeras carrying various subcellular localization signals in <italic>N. benthamiana</italic> leaves revealed that a nuclear localization of Avr2 is required to trigger I-2-dependent cell death. Nuclear exclusion of Avr2 prevented its activation of I-2, suggesting that Avr2 is recognized by I-2 in the nucleus.</p>