Bigeard, J. | bioRxiv Science

bioRxiv2025

Enhancement of Arabidopsis growth by Enterobacter sp. SA187 under elevated CO2 is dependent on ethylene signalling activation and primary metabolism reprogramming

As atmospheric CO2 levels continue to increase, optimizing the CO2 fertilization effect which often falls short of its potential due to the physiological and metabolic limitations of plants becomes crucial. This study investigates the role of Enterobacter sp. SA187 (SA187), a plant growth-promoting bacterium, in enhancing growth and development of Arabidopsis thaliana under elevated atmospheric CO2 (eCO2) conditions. While SA187 inoculation did not have major effects under ambient CO2, it was found to significantly enhance root and shoot biomass, and to increase N- and reduce C-contents under eCO2. Moreover, transcriptomics and metabolomics suggested that SA187 modulated phytohormonal homeostasis, with activation of the salicylic acid, jasmonic acid and ethylene signalling pathways, and increased primary metabolism including the TCA cycle, N and carbohydrate metabolisms. Finally, the growth-promoting effects of SA187 were shown to be mediated through ethylene-dependent pathways, as evidenced with the ethylene-insensitive mutant ein2-1 which did not show similar benefits in plant fresh weight and altered gene expression. This beneficial plant-microbe interaction under eCO2 in a non-leguminous plant highlights a novel aspect of microbial influence on plant physiology in the context of climate change. These insights underscore the potential of utilizing SA187 to enhance plant performance and adaptability in future high CO2 environments, providing a sustainable approach to agricultural productivity as global CO2 levels increase.

plant biology↗

bioRxiv2021

Both transient and sustained MPK3/6 activities positively control expression of NLR genes in PTI and ETI.

Arabidopsis thaliana Mitogen Activated Protein Kinases 3 and 6 (MPK3/6) are known to be activated transiently in PAMP-Triggered Immunity (PTI) and durably in Effector-Triggered Immunity (ETI). However the functional differences between these two kinds of activation kinetics and how they allow coordination of the two layers of plant immunity remain poorly understood. Here, by analysing suppressors of the phenotype caused by a constitutively active form of MPK3, we demonstrate that ETI-mediating nucleotide-binding domain leucine-rich repeat receptors (NLRs) and NLR signaling can act downstream of MPK3 activities. Moreover we provide evidence that both sustained and transient MPK3/6 activities positively control the expression of at least two NLR genes, AT3G04220 and AT4G1110. We further show that the ETI regulators NDR1 and EDS1 also contribute to the upregulations of these two NLRs not only in an ETI context but also in a PTI context. Remarkably, while in ETI, MPK3/6 activities are dependent on NDR1 and EDS1, they are not in PTI, suggesting that if the same actors are involved in the two layers of immunity, the way they are interconnected is different. Finally we demonstrate that expression of the NLR AT3G04220 is sufficient to induce expression of defense genes from the SA branch. Overall this study enlarges our knowledge of MPK3/6 functions during immunity and gives a new insight into the intrication of PTI and ETI.

plant biology↗