A SABATH family enzyme regulates development via the gibberellin-related pathway in the liverwort Marchantia polymorpha
Authors: Kawamura, S., Shimokawa, E., Ito, M., Nakamura, I., Kanazawa, T., Iwano, M., Sun, R., Yoshitake, Y., Yamaoka, S., Yamaguchi, S., Ueda, T., Kato, M., Kohchi, T.
The study identified 12 SABATH methyltransferase genes in the liverwort Marchantia polymorpha and demonstrated that MpSABATH2 is crucial for normal thallus growth and gemma cup formation. Loss‑of‑function mutants displayed developmental phenotypes reminiscent of far‑red light responses, which were linked to gibberellin metabolism and could be partially rescued by inhibiting GA biosynthesis or supplying the GA precursor ent‑kaurenoic acid. These findings suggest that SABATH enzymes independently evolved regulatory roles in land‑plant development.
The study establishes a tractable system using the large bloom-forming diatom Coscinodiscus granii and its natural oomycete parasite Lagenisma coscinodisci, enabling manual isolation of single host cells and stable co-cultures. High‑quality transcriptomes for both partners were assembled, revealing diverse oomycete effectors and a host transcriptional response involving proteases and exosome pathways, while also profiling the co‑occurring heterotrophic flagellate Pteridomonas sp. This tripartite platform provides a unique marine model for dissecting molecular mechanisms of oomycete‑diatom interactions.
The study demonstrates that carbon availability promotes gemma cup formation in Marchantia polymorpha by activating cytokinin signaling, which up‑regulates the transcription factors MpGCAM1 and MpSTG. Pharmacological and genetic manipulations showed that cytokinin accumulation in response to sucrose and high light is sufficient to overcome low‑sucrose repression, and that this pathway operates independently of KAI2A‑MAX2 mediated karrikin signaling. The findings suggest a conserved carbon‑cytokinin interaction governing developmental plasticity across land plants.
The study demonstrates that infiltrating Nicotiana benthamiana leaves with specific nopaline-type Agrobacterium tumefaciens strains dramatically increases local glandular trichome density within 15 days, an effect linked to the bacterial trans-zeatin synthase (tzs) gene that produces the cytokine trans‑zeatin. This simple Agrobacterium‑mediated approach enables direct comparison of high‑density trichome regions with adjacent isogenic tissue on the same leaf.
The study examined the pre‑activation state of the rice NLR pair Pik‑1 (sensor) and Pik‑2 (helper) when transiently expressed in Nicotiana benthamiana leaves. Both wild‑type and engineered Pik‑1 variants constitutively associate with Pik‑2 to form ~1 MDa hetero‑oligomeric complexes that localize to the plasma membrane in the absence of effector. These results reveal that some NLRs exist as pre‑assembled membrane‑associated complexes prior to pathogen perception.
Infiltration of Nicotiana benthamiana leaves with Agrobacterium tumefaciens strain GV3101 carrying the pMP90 Ti plasmid triggers de novo formation of capitate glandular trichomes and elevates acyl‑sugar production, an effect absent with other strains. The responsible factor is the trans‑zeatin synthase (tzs) gene on pMP90, and exogenous application of cytokinins (trans‑zeatin or benzylaminopurine) alone can reproduce trichome induction, linking cytokinin signaling to trichome development. The study highlights that Agrobacterium-mediated transient assays can have unintended developmental and biochemical impacts, recommending strain testing to mitigate such effects.
The study evaluated a transgenic soybean line (VPZ-34A) expressing Arabidopsis VDE, PsbS, and ZEP for combined improvements in light‑use efficiency and carbon assimilation under ambient and elevated CO2 in a FACE experiment. While VPZ‑34A showed enhanced maximum quantum efficiency of PSII under fluctuating light, it did not increase carbon assimilation efficiency or yield, and transcriptome analysis revealed limited gene expression changes. The results suggest that VPZ‑mediated photosynthetic gains are insufficient to boost productivity under elevated CO2.
Causes and consequences of experimental variation in Nicotiana benthamiana transient expression
Authors: Tang, S. N., Szarzanowicz, M., Lanctot, A., Sirirungruang, S., Kirkpatrick, L. D., Drako, K., Alamos, S., Cheng, L., Waldburger, L. M., Liu, S., Huang, L., Akyuz Turumtay, E., Kazaz, S., Baidoo, E., Eudes, A., Thompson, M., Shih, P.
The study systematically examines sources of variability in Agrobacterium tumefaciens-mediated transient expression in Nicotiana benthamiana, analyzing a large dataset of 1,915 plants collected over three years. It demonstrates that normalization methods must be validated for each experimental context and provides a statistical model and power analysis framework to determine appropriate sample sizes for detecting specific effect sizes, offering practical guidelines to improve reproducibility in quantitative plant and synthetic biology studies.
The study characterizes the liverwort-specific NPR protein (MpNPR) in Marchantia polymorpha, demonstrating that it controls oil body formation and confers resistance to gastropod herbivory through interaction with the transcription factor MpERF13. Loss- or gain-of-function of MpNPR disrupts MpERF13‑dependent gene expression and compromises defense against snail feeding, revealing a lineage‑specific immune pathway distinct from tracheophyte NPR functions.
The study demonstrates that red and blue light have opposing effects on thallus growth orientation in Marchantia polymorpha, with red light promoting epinasty and blue light promoting hyponasty. Loss-of-function mutants in the respective photoreceptors and BBX transcription factors reveal antagonistic interactions that balance thallus flatness under white light. Time‑resolved transcriptomics identified rapid light‑induced genes, including all six MpBBX members, whose mutant phenotypes support this antagonistic model.