Received November 20, 2001
Accepted December 6, 2001
Tomato Transcription Factors Pti4, Pti5, and Pti6 Activate Defense Responses When
Expressed in Arabidopsis
Yong-Qiang Gu 1*, Mary C. Wildermuth 2, Suma Chakravarthy 1, Ying-Tsu Loh 3, Caimei Yang 1, Xiaohua He 1, Yu Han 1, and Gregory B. Martin 4
1
Boyce Thompson Institute for Plant Research, Ithaca, New York 14853
2
Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115;
Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts
02114
3
Department of Agronomy, Purdue University, West Lafayette, Indiana 47907
4
Boyce Thompson Institute for Plant Research, Ithaca, New York 14853; Department
of Plant Pathology, Cornell University, Ithaca, New York 14853
* To whom correspondence should be addressed.
The Pti4, Pti5, and Pti6 proteins from tomato were identified based on their interaction
with the product of the Pto disease resistance gene, a Ser-Thr protein kinase.
They belong to the ethylene-response factor (ERF) family of plant-unique transcription
factors and bind specifically to the GCC-box cis element present in the
promoters of many pathogenesis-related (PR) genes. Here, we show that these
tomato ERFs are localized to the nucleus and function in vivo as transcription activators
that regulate the expression of GCC box--containing PR genes. Expression
of Pti4, Pti5, or Pti6 in Arabidopsis activated the expression
of the salicylic acid--regulated genes PR1 and PR2. Expression
of jasmonic acid-- and ethylene-regulated genes, such as PR3, PR4
, PDF1.2, and Thi2.1, was affected differently by each of
the three tomato ERFs, with Arabidopsis-Pti4 plants having very high levels
of PDF1.2 transcripts. Exogenous application of salicylic acid to Arabidopsis-
Pti4 plants suppressed the increased expression of PDF1.2 but further
stimulated PR1 expression. Arabidopsis plants expressing Pti4 displayed
increased resistance to the fungal pathogen Erysiphe orontii and increased
tolerance to the bacterial pathogen Pseudomonas syringae pv tomato
. These results indicate that Pti4, Pti5, and Pti6 activate the expression of a wide
array of PR genes and play important and distinct roles in plant defense.
