A new study published in the Molecular Plant-Microbe Interactions journal offers new evidence that microbes are trying to hijack the plant immune system to induce disease while also offering insights into a recently identified mechanism.
A wide range of pathogens affect plants and cause various diseases, which can decrease crop yields. Pathogens secrete effector proteins into plant cells during infection. A few of these proteins are directed at the plant proteasomal degradation machinery, which is in charge of recycling proteins to control cell processes.
Certain E1, E2, and E3-ligase proteins have been linked to plant resistance or vulnerability to invasion by pathogens. SDIR1 (SALT- AND DROUGHT-INDUCED RING FINGER1) is an E3-ligase that degrades plant hormone regulators of abscisic acid (ABA) in response to drought stress.
Ramu Vemanna of the Regional Center for Biotechnology and his collaborators at the Noble Research Institute described a new way in which SDIR1 influences plant immunity during pathogen-borne stress.
They discovered that silencing SDIR1 inhibited the growth of host-specific and nonhost Pseudomonas syringae strains in the model plant Nicotiana benthamiana, as well as disease symptom progression in the model plant Arabidopsis thaliana. Overexpression of SDIR1 in A. thaliana enabled even nonhost P. syringae strain to proliferate and lead to disease symptoms.
Unlike the findings obtained when plants were challenged with biotrophic bacterial pathogens, SDIR1 overexpression lines are resistant to the necrotrophic bacterial pathogen Erwinia carotovora. SDIR1 overexpression plants exhibited more ABA and jasmonic acid (JA)—a plant hormone that plays a role in the defense of plants against necrotrophic pathogens.
SDIR1 overexpression resulted in reduced expression of genes that repress JA-mediated protection (signaling genes JAZ8 and JAZ7) in response to host-specific P. syringae strain DC3000.
SDIR1’s interaction with the JA pathway suggests that it is a susceptibility gene for biotrophic pathogens such as P. syringae while also being active in defending against necrotrophic pathogens such as E. carotovora.
These findings open up new research avenues to discover the SDIR1-associated mechanisms that can harness the crop improvement by altering different plant traits. The SDIR1 is also a potential target for genome editing in order to enhance crop protection. If the structure of SDIR1 is solved, more opportunities evolve to design CRISPR targets and drug-like molecules to protect crops from pathogens and abiotic stresses.”
Ramu Vemanna, Regional Center for Biotechnology, Noble Research Institute
Ramu, V. S., et al. (2021) A Novel Role of Salt- and Drought-Induced RING 1 Protein in Modulating Plant Defense Against Hemibiotrophic and Necrotrophic Pathogens. Molecular Plant-Microbe Interactions. doi.org/10.1094/MPMI-09-20-0257-R.