S. Rustgi, E. Boex-Fontvieille, C. Reinbothe, D. von Wettstein, S. Reinbothe
Proceedings of the National Academy of Sciences, 2017
Significance Nature has evolved highly specific protease inhibitors comprising serpin and Kunitz proteins. In humans, loss- or gain-of-function mutations in many protease inhibitor (PI) genes lead to compromised innate immune responses, dementia, thrombosis, and other diseases. Here, we report how plants make use of serpin and Kunitz PIs to control papain-like cysteine proteases over plant development and exploit them for defense. Proteolytic enzymes (proteases) participate in a vast range of physiological processes, ranging from nutrient digestion to blood coagulation, thrombosis, and beyond. In plants, proteases are implicated in host recognition and pathogen infection, induced defense (immunity), and the deterrence of insect pests. Because proteases irreversibly cleave peptide bonds of protein substrates, their activity must be tightly controlled in time and space. Here, we report an example of how nature evolved alternative mechanisms to fine-tune the activity of a cysteine protease dubbed RD21 (RESPONSIVE TO DESICCATION-21). One mechanism in the model plant Arabidopsis thaliana studied here comprises irreversible inhibition of RD21’s activity by Serpin1, whereas the other mechanism is a result of the reversible inhibition of RD21 activity by a Kunitz protease inhibitor named water-soluble chlorophyll-binding protein (WSCP). Activity profiling, complex isolation, and homology modeling data revealed unique interactions of RD21 with Serpin1 and WSCP, respectively. Expression studies identified only partial overlaps in Serpin1 and WSCP accumulation that explain how RD21 contributes to the innate immunity of mature plants and arthropod deterrence of seedlings undergoing skotomorphogenesis and greening.
Cited by 3 publications.
Field of study: Biology