Pto mutants differentially activate Prf-dependent, avrPto-independent resistance and gene-for-gene resistance.
Pto confers disease resistance to Pseudomonas syringae pv tomato carrying the cognate avrPto gene. Overexpression of Pto under the cauliflower mosaic virus 35S promoter activates spontaneous lesions and confers disease resistance in tomato (Lycopersicon esculentum) plants in the absence of avrPto. Here, we show that these AvrPto-independent defenses require a functional Prf gene. Several Pto-interacting (Pti) proteins are thought to play a role in Pto-mediated defense pathways. To test if interactions with Pti proteins are required for the AvrPto-independent defense responses by Pto overexpression, we isolated several Pto mutants that were unable to interact with one or more Pti proteins, but retained normal interaction with AvrPto. Overexpression of two mutants, Pto(G50S) and Pto(R150S), failed to activate AvrPto-independent defense responses or confer enhanced resistance to the virulent P. s. pv tomato. When introduced into plants carrying 35S::Pto, 35S::Pto(G50S) dominantly suppressed the AvrPto-independent resistance caused by former transgene. 35S::Pto(G50S) also blocked the induction of a number of defense genes by the wild-type 35S::Pto. However, 35S::Pto(G50S) and 35S::Pto(R150S) plants were completely resistant to P. s. pv tomato (avrPto), indicating a normal gene-for-gene resistance. Furthermore, 35S::Pto(G50S) plants exhibited normal induction of defense genes in recognition of avrPto. Thus, the AvrPto-independent defense activation and gene-for-gene resistance mediated by Pto are functionally separable.
Xiao
Fangming
F
Department of Plant Pathology, Kansas State University, Manhattan, Kansas 66506, USA.
Lu
Ming
M
Li
Jianxiong
J
Zhao
Tiehan
T
Yi
Seung Young
SY
Thara
Venkatappa K
VK
Tang
Xiaoyan
X
Zhou
Jian-Min
JM
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D007113:Immunity, Innate / Q000235:genetics; D018551:Solanum lycopersicum / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D009154:Mutation; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D011485:Protein Binding; D025941:Protein Interaction Mapping; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D011549:Pseudomonas / Q000235:genetics / Q000254:growth & development
D001426:Bacterial Proteins; D010940:Plant Proteins; C120613:Prf protein, Lycopersicon esculentum; C081695:avrPto protein, Pseudomonas syringae; C084354:Pto protein, Lycopersicon; D017346:Protein Serine-Threonine Kinases