Serpin1 and WSCP differentially regulate the activity of the cysteine protease RD21 during plant development in Arabidopsis thaliana

Abstract

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.protease | protease inhibitor | WSCP | Serpin1 | RD21

N‐terminomics reveals control of Arabidopsis seed storage proteins and proteases by the Arg/N‐end rule pathway

“…RD21A is responsible for the dominant PLCP activity in Arabidopsis extracts (Gu et al ., ) and has been associated with functions in immunity, herbivore defence, senescence, cell death and response to stresses (Shindo et al ., ; Lampl et al ., ; Rustgi et al ., ; and references therein). Following activation via a proteolytic cascade, RD21A activity is tightly regulated at different developmental stages by a Kunitz‐type protease inhibitor, water‐soluble Chl binding protein (reversible inhibition) and by AtSerpin1 (irreversible inhibition) (Lampl et al ., ; Boex‐Fontvieille et al ., ; Rustgi et al ., ). RD21A protein is also subject to ubiquitin‐dependent degradation mediated by the E3 ligase AtAIRP3/LOG2 (Kim & Kim, ).…”

Ten Prominent Host Proteases in Plant-Pathogen Interactions

“…However, atserpin1 mutants do not show a phenotype and AtSERPIN1 also regulates PCD via AtMC1 [ 30 ]. Besides AtSERPIN1, RD21 is also regulated by kunitz inhibitor WSCP [ 60 ], protein di-isomerase PDI5 [ 61 ], and other mechanisms [ 62 ]. This makes RD21 regulation a challenging and intriguing question to resolve.…”

An Alternative Nested Reading Frame May Participate in the Stress-Dependent Expression of a Plant Gene

“…Plant KPIs are normally represented by multigene families ranging from several members to several tens of members, as in the case of the poplar ( Populus trichocarpa ), where a wide range of within-family identity was found from low (38%) to high homology (96%) (Major and Constabel, 2008 ; Philippe et al, 2009 ). Some members of this family show their activity in organs only under stressful conditions (Rustgi et al, 2017 ). The upstream regions of the NbMLP1, NbMLP2 , and NbMLP3 genes were identified, and promoter elements responsible for defense responses were studied to explain the activation of these genes during stress (Goodwin et al, 2012 ).…”