title: Tomato-Pseudomonas syringae interactions under elevated CO₂ concentration: the role of stomata.
abstract: Increasing atmospheric CO₂ concentrations ([CO₂]) in agricultural and natural ecosystems is known to reduce plant stomatal opening, but it is unclear whether these CO₂-induced stomatal alterations are associated with foliar pathogen infections. In this study, tomato plants were grown under ambient and elevated [CO₂] and inoculated with Pseudomonas syringae pv. tomato strain DC3000, a strain that is virulent on tomato plants. We found that elevated [CO₂] enhanced tomato defence against P. syringae. Scanning electron microscopy analysis revealed that stomatal aperture of elevated [CO₂] plants was considerably smaller than their ambient counterparts, which affected the behaviour of P. syringae bacteria on the upper surface of epidermal peels. Pharmacological experiments revealed that nitric oxide (NO) played a role in elevated [CO₂]-induced stomatal closure. Silencing key genes involved in NO generation and stomatal closing, nitrate reductase (NR) and guard cell slow-type anion channel 1 (SLAC1), blocked elevated [CO₂]-induced stomatal closure and resulted in significant increases in P. syringae infection. However, the SLAC1-silenced plants, but not the NR-silenced plants, still had significantly higher defence under elevated [CO₂] compared with plants treated with ambient [CO₂]. Similar results were obtained when the stomata-limiting factor for P. syringae entry was excluded by syringe infiltration inoculation. These results indicate that elevated [CO₂] induces defence against P. syringae in tomato plants, not only by reducing the stomata-mediated entry of P. syringae but also by invoking a stomata-independent pathway to counteract P. syringae. This information is valuable for designing proper strategies against bacterial pathogens under changing agricultural and natural ecosystems.
authors.affiliation: Department of Horticulture, Zijingang Campus, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China Tea Research Insititute, Chinese Academy of Agricultural Science, Hangzhou, 310008, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Horticulture, Zijingang Campus, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China.
authors.forename: Zenghui
authors.initials: Z
authors.lastname: Sun
authors.affiliation: Department of Horticulture, Zijingang Campus, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China.
authors.forename: Shujun
authors.initials: S
authors.lastname: Shao
authors.affiliation: Department of Horticulture, Zijingang Campus, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Department of Horticulture, Zijingang Campus, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China.
authors.forename: Golam Jalal
authors.initials: GJ
authors.lastname: Ahammed
authors.affiliation: Department of Horticulture, Zijingang Campus, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China.
authors.forename: Guanqun
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Department of Horticulture, Zijingang Campus, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China Zhuanghang Experimental Station, Shanghai Academy of Agricultural Sciences, 1000 Jinqi Road, Shanghai, 201403, China.
authors.forename: Yuping
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: Department of Horticulture, Zijingang Campus, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Department of Horticulture, Zijingang Campus, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China.
authors.forename: Xiaojian
authors.initials: X
authors.lastname: Xia
authors.affiliation: Department of Horticulture, Zijingang Campus, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China.
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Department of Horticulture, Zijingang Campus, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China Key Laboratory of Horticultural Plants Growth, Development and Quality Improvement, Agricultural Ministry of China, 866 Yuhangtang Road, Hangzhou, 310058, China.
authors.forename: Jingquan
authors.initials: J
authors.lastname: Yu
authors.affiliation: Department of Horticulture, Zijingang Campus, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China Key Laboratory of Horticultural Plants Growth, Development and Quality Improvement, Agricultural Ministry of China, 866 Yuhangtang Road, Hangzhou, 310058, China kaishi@zju.edu.cn.
authors.forename: Kai
authors.initials: K
authors.lastname: Shi
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D020868:Gene Silencing; D018551:Solanum lycopersicum / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology*; D010935:Plant Diseases / Q000382:microbiology*; D054046:Plant Stomata / Q000378:metabolism* / Q000382:microbiology; D044224:Pseudomonas syringae / Q000502:physiology*; D036226:Seedlings / Q000378:metabolism / Q000382:microbiology
chemical_list: D002245:Carbon Dioxide
keywords: Elevated CO2; Pseudomonas syringae; Solanum lycopersicum; nitric oxide; stomata.