Morcillo, R. J. L. | bioRxiv Science

bioRxiv2025

CLPC2 plays specific roles in CLP complex-mediated regulation of growth, photosynthesis, embryogenesis and response to growth-promoting microbial compounds

In Arabidopsis, exposure to growth-promoting microbial volatile compounds (VCs) enhances CLPC2 levels. This chaperone forms part of the CLP protease complex, which ensures the correct functioning of essential processes in plastids. Previous studies indicated considerable functional redundancy of CLPC2 with its dominant paralogue CLPC1. However, the function and action mechanism of CLPC2 still remain unknown. Here we found that CLPC2-lacking clpc2-2 mutants were unresponsive to microbial VCs, whereas clpc1-1 knockout mutants exhibited a WT-like response to VCs when grown on sucrose-containing medium. Unlike clpc1-1, clpc2-2 plants presented a fully functional photosystem II and lower than WT stomatal conductance. Furthermore, clpc2-2 plants, but not clpc1-1 plants, produced wrinkled seeds with delayed embryonic development and reduced postgerminative establishment rates that resembled those of mutants lacking P and R components of the CLP proteolytic core. Proteomic analyses revealed that knocking out of CLPC2 enhanced the levels of chloroplastic proteins that are essential for growth, embryo development and seedling establishment. These changes differed from those promoted by the lack of CLPC1, but partially resembled those promoted by CLPPR core inactivation. Nearly 40% of the proteins differentially accumulated by the lack of CLPC2 were VC-responsive. Notably, 35S promoter-driven CLPC2 expression promoted changes in the proteome similar to those promoted by the lack of CLPC1. Collectively, our findings highlighted contrasting functional and molecular specificities for CLPC1 and CLPC2, and provided strong evidence that CLPC2 plays specific roles in CLP complex-mediated regulation of plant growth, photosynthesis, embryogenesis, postgerminative seedling establishment and microbial VC responsiveness.

plant biology↗

bioRxiv2020

Latent defense response to non-pathogenic microbial factors impairs plant-rhizobacteria mutualism

Unlike pathogens that trigger plant defense responses, commensal or beneficial microbes are compatible with plants and do not elicit a defense response. An assumption underlying the compatibility is that plants are inert in mounting a defense response to non-pathogenic microbial factors. However, the mechanisms underlying this inertness in defense are unknown. Here a forward genetic screen led to the isolation of an Arabidopsis mutant displaying a new type of immunity which we named as latent defense response (LDR) to a beneficial rhizobacterium. The mutant, known as gp1 for Growth-Promotion 1, is impaired in rhizobacteria-induced plant growth-promotion due to disrupted oleic acid homeostasis and consequent activation of defense responses. Several bacterial volatile compounds trigger LDR in gp1 but not wild type plants. GP1 dysfunction strongly represses colonization of the beneficial rhizobacterium and alters root-associated microbiota. Our findings reveal a hidden layer of plant defense, LDR, which is suppressed by GP1 to allow mutualistic association between plants and beneficial rhizobacteria. One Sentence SummaryA hidden layer of host immunity against non-pathogenic microbes leads to plant incompatibility with beneficial rhizobacteria.

plant biology↗