A genetic screen reveals Arabidopsis stomatal and/or apoplastic defenses against Pseudomonas syringae pv. tomato DC3000.


Bacterial infection of plants often begins with colonization of the plant surface, followed by entry into the plant through wounds and natural openings (such as stomata), multiplication in the intercellular space (apoplast) of the infected tissues, and dissemination of bacteria to other plants. Historically, most studies assess bacterial infection based on final outcomes of disease and/or pathogen growth using whole infected tissues; few studies have genetically distinguished the contribution of different host cell types in response to an infection. The phytotoxin coronatine (COR) is produced by several pathovars of Pseudomonas syringae. COR-deficient mutants of P. s. tomato (Pst) DC3000 are severely compromised in virulence, especially when inoculated onto the plant surface. We report here a genetic screen to identify Arabidopsis mutants that could rescue the virulence of COR-deficient mutant bacteria. Among the susceptible to coronatine-deficient Pst DC3000 (scord) mutants were two that were defective in stomatal closure response, two that were defective in apoplast defense, and four that were defective in both stomatal and apoplast defense. Isolation of these three classes of mutants suggests that stomatal and apoplastic defenses are integrated in plants, but are genetically separable, and that COR is important for Pst DC3000 to overcome both stomatal guard cell- and apoplastic mesophyll cell-based defenses. Of the six mutants defective in bacterium-triggered stomatal closure, three are defective in salicylic acid (SA)-induced stomatal closure, but exhibit normal stomatal closure in response to abscisic acid (ABA), and scord7 is compromised in both SA- and ABA-induced stomatal closure. We have cloned SCORD3, which is required for salicylic acid (SA) biosynthesis, and SCORD5, which encodes an ATP-binding cassette (ABC) protein, AtGCN20/AtABCF3, predicted to be involved in stress-associated protein translation control. Identification of SCORD5 begins to implicate an important role of stress-associated protein translation in stomatal guard cell signaling in response to microbe-associated molecular patterns and bacterial infection.





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Publication Info

Zeng, Weiqing, Alexandre Brutus, James M Kremer, John C Withers, Xiaoli Gao, A Daniel Jones and Sheng Yang He (2011). A genetic screen reveals Arabidopsis stomatal and/or apoplastic defenses against Pseudomonas syringae pv. tomato DC3000. PLoS pathogens, 7(10). p. e1002291. 10.1371/journal.ppat.1002291 Retrieved from https://hdl.handle.net/10161/21725.

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Sheng-Yang He

Benjamin E. Powell Distinguished Professor of Biology

Interested in the fascinating world of plants, microbes or inter-organismal communication and co-evolution? Please contact Prof. Sheng-Yang He (shengyang.he@duke.edu; hes@msu.edu).

Millions of years of co-evolution between plants and microbes have resulted in an intricate web of attack, counter-attack, decoy, and hijacking mechanisms in biology. Moreover, co-evolution between plants and microbes is greatly impacted by ongoing climate change. In our lab, we probe “host-microbe-climate” interactions to answer the following fundamental questions: (1) How do microbial pathogens infect a susceptible host? (2) How do plants select beneficial microbiomes to ensure health? (3) How do climate conditions impact disease and immunity?      

We use contemporary methods to address these questions, including those commonly used in molecular genetics, genomics, biochemistry, cell biology, bioinformatics, microbiology, plant biology, co-evolution and infectious disease biology.    

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