B03

Effector-induced manipulation of host polyamine levels

Understanding of how a TAL effector of the root pathogen Ralstonia solanacearum promotes bacterial wilt disease

Ralstonia solanacearum is a globally distributed, broad-host plant pathogen, infecting many important crops. It infects plant roots and injects effector proteins into host cells, hijacking cellular functions and manipulating the host. We are studying Brg11, an R. solanacearum effector protein that causes increased expression of the host enzyme arginine decarboxylase (ADC) (Wu et al., 2019). ADC is involved in synthesis of polyamines, a group of essential metabolites involved in growth, development, and stress responses. Based on preliminary results, we have two hypotheses as to how Brg11-induced metabolic changes aid R. solanacearum infection. Firstly, over-expression of ADC boosts hydroxycinnamic acid-polyamine conjugates (HCA-PAs), a group of metabolites with antimicrobial activities (Liu et al., 2018). R. solanacearum is able to degrade such compounds (Lowe et al., 2015), leading to the hypothesis that Brg11 induces HCA-PAs to inhibit growth of niche competitors. Our second hypothesis is that the Brg11-induced increase in PA levels and their conjugation to HCAs could deplete the HCA pool, which is needed for the synthesis of suberin/lignin-based cell wall reinforcements to ward off R. solanacearum. A third working model suggests that PAs may induce lateral root formation, creating natural root openings, favouring infection by R. solanacearum.

REFERENCES
Wu et al. (2019), Cell Host Microbe 26, 638-649.
Liu et al. (2022) Front Plant Sci 13, 922119.
Lowe et al. (2015) Mol Plant-Microbe Interact 28, 286-297.

Principal Investigator: Prof. Dr. Thomas Lahaye, ZMBP – General Genetics, University of Tübingen