Xanthomonas translucens commandeers the host rate-limiting step in ABA biosynthesis for disease susceptibility

Authors: PENG, ZHAO - University Of Florida; HU, YING - Kansas State University; ZHANG, JUNLI - University Of Florida; HUGUET-TAPIA, JOSE - University Of Florida; Block, Anna; PARK, SUNGHUN - Kansas State University; SAPKOTA, SURAJ - North Dakota State University; LIU, ZHAOHUI - North Dakota State University; LIU, SANZHEN - Kansas State University; WHITE, FRANK - University Of Florida

Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/13/2019
Publication Date: 10/15/2019
Citation: Peng, Z., Hu, Y., Zhang, J., Huguet-Tapia, J.C., Block, A.K., Park, S., Sapkota, S., Liu, Z., Liu, S., White, F.F. 2019. Xanthomonas translucens commandeers the host rate-limiting step in ABA biosynthesis for disease susceptibility. Proceedings of the National Academy of Sciences. 42,vol 16, 20938-20948. https://doi.org/10.1073/pnas.1911660116.
DOI: https://doi.org/10.1073/pnas.1911660116

Interpretive Summary: Bacterial leaf streak is an important global disease of wheat. Understanding how these bacteria cause this disease will help guide the development of approaches for its control. Investigation of the pathogenic mechanisms of these bacteria by researchers from the University of Florida, Kansas State University, North Dakota State University and USDA-ARS, Center for Medical, Agricultural, and Veterinary Medicine in Gainesville, FL revealed that they can control the production of a hormone in wheat that regulates water balance within the plant. This disruption of the plant’s water balance allows these bacteria to grow and travel more easily within the plant leading to increased disease. Developing plants whose water balance can not be hijacked in this manner would enable them to have increased resistance to bacterial leaf streak, and thus increased wheat yields.

Technical Abstract: Plants are vulnerable to disease through pathogen manipulation of phytohormone levels, which otherwise regulate development, abiotic and biotic responses. Here, we show the wheat pathogen X. translucens pv. undulosa elevates expression of the host gene encoding nine-cis-epoxycarotenoid dioxygenase (TaNCED-5BS), which catalyzes the rate-limiting step in the biosynthesis of the phytohormone abscisic acid (ABA) and a component of a major abiotic stress response pathway, to promote disease susceptibility. Gene induction is mediated by a type III transcription activator-like (TAL) effector. The induction of TaNCED-5BS results in elevated ABA levels, reduced host transpiration and water loss, enhanced spread of bacteria in infected leaves, and decreased expression of the central defense gene TaNPR1. The results represent a novel appropriation of host physiology by a bacterial virulence effector.