Bringing Plant Immunity to Light: A Genetically Encoded, Bioluminescent Reporter of Pattern-Triggered Immunity in Nicotiana benthamiana

The Phytophthora infestans effector Pi05910 suppresses and destabilizes host glycolate oxidase StGOX4 to promote plant susceptibility

Phytophthora infestans is a notorious oomycete pathogen that causes potato late blight. It secretes numerous effector proteins to manipulate host immunity. Understanding mechanisms underlying their host cell manipulation is crucial for developing disease resistance strategies. Here, we report that the conserved RXLR effector Pi05910 of P. infestans is a genotype-specific avirulence elicitor on potato variety Longshu 12 and contributes virulence by suppressing and destabilizing host glycolate oxidase StGOX4. By performing co-immunoprecipitation, yeast-two-hybrid assays, luciferase complementation imaging, bimolecular fluorescence complementation and isothermal titration calorimetry assays, we identified and confirmed potato StGOX4 as a target of Pi05910. Further analysis revealed that StGOX4 and its homologue NbGOX4 are positive immune regulators against P. infestans, as indicated by infection assays on potato and Nicotiana benthamiana overexpressing StGOX4 and TRV-NbGOX4 plants. StGOX4-mediated disease resistance involves enhanced reactive oxygen species accumulation and activated the salicylic acid signalling pathway. Pi05910 binding inhibited enzymatic activity and destabilized StGOX4. Furthermore, mutagenesis analyses indicated that the 25th residue (tyrosine, Y25) of StGOX4 mediates Pi05910 binding and is required for its immune function. Our results revealed that the core RXLR effector of P. infestans Pi05910 suppresses plant immunity by targeting StGOX4, which results in decreased enzymatic activity and protein accumulation, leading to enhanced plant susceptibility.

An improved pathway for autonomous bioluminescence imaging in eukaryotes

The discovery of the bioluminescence pathway in the fungus Neonothopanus nambi enabled engineering of eukaryotes with self-sustained luminescence. However, the brightness of luminescence in heterologous hosts was limited by performance of the native fungal enzymes. Here we report optimized versions of the pathway that enhance bioluminescence by one to two orders of magnitude in plant, fungal and mammalian hosts, and enable longitudinal video-rate imaging.

Phytomelatonin: A key regulator of redox and phytohormones signaling against biotic/abiotic stresses

Plants being sessile in nature, are exposed to unwarranted threats as a result of constantly changing environmental conditions. These adverse factors can have negative impacts on their growth, development, and yield. Hormones are key signaling molecules enabling cells to respond rapidly to different external and internal stimuli. In plants, melatonin (MT) plays a critical role in the integration of various environmental signals and activation of stress-response networks to develop defense mechanisms and plant resilience. Additionally, melatonin can tackle the stress-induced alteration of cellular redox equilibrium by regulating the expression of redox hemostasis-related genes and proteins. The purpose of this article is to compile and summarize the scientific research pertaining to MT's effects on plants' resilience to biotic and abiotic stresses. Here, we have summarized that MT exerts a synergistic effect with other phytohormones, for instance, ethylene, jasmonic acid, and salicylic acid, and activates plant defense-related genes against phytopathogens. Furthermore, MT interacts with secondary messengers like Ca²⁺, nitric oxide, and reactive oxygen species to regulate the redox network. This interaction triggers different transcription factors to alleviate stress-related responses in plants. Hence, the critical synergic role of MT with diverse plant hormones and secondary messengers demonstrates phytomelatonin's importance in influencing multiple mechanisms to contribute to plant resilience against harsh environmental factors.