CRK2 controls the spatiotemporal distribution of QSK1 at plasma membrane during osmotic stress
Authors: Jindal, S., Zeiner, A., Bondar, A., Neubergerova, M., Stolze, S. C., Harzen, A., Colina, F. J., Liekens, S., Pääkkönen, M., Merilahti, J., Kulich, I., Pleskot, R., Nakagami, H., Wrzaczek, M.
The study demonstrates that in Arabidopsis, the receptor-like kinase CRK2 phosphorylates and retains QSK1 at the plasma membrane under normal conditions, preventing excess callose deposition at plasmodesmata. Osmotic stress leads to dephosphorylation of QSK1, allowing its relocalization to plasmodesmata where it promotes stress‑induced callose accumulation, while CRK2 later moves to plasmodesmata to negatively regulate this deposition, revealing a dynamic gating mechanism.
The authors used a bottom‑up thermodynamic modelling framework to investigate how plants decode calcium signals, starting from Ca2+ binding to EF‑hand proteins and extending to higher‑order decoding modules. They identified six universal Ca2+-decoding modules that can explain variations in calcium sensitivity among kinases and provide a theoretical basis for interpreting calcium signal amplitude and frequency in plant cells.
CYSTEINE-RICH RLK2 regulates development via callose synthase-dependent symplastic transport in Arabidopsis
Authors: Zeiner, A., Krasensky-Wrzaczek, J., Jindal, S., Hajny, J., Sharma, M., Morina, F., Andresen, E., Pääkkönen, M., Küpper, H., Merilahti, J., Wrzaczek, M.
The study reveals that Arabidopsis CRK2 phosphorylates the callose synthases CALS1 and CALS3, influencing callose deposition at plasmodesmata and thereby affecting phloem loading and source‑to‑sink transport. Loss of CRK2 leads to starch accumulation in older leaves, a phenotype rescued by introducing functional CALS1 or CALS3 alleles, indicating that CRK2, CALS1, and CALS3 jointly regulate growth and development through control of intercellular transport.
The authors compiled and standardized published data on Rubisco dark inhibition for 157 flowering plant species, categorizing them into four inhibition levels and analyzing phylogenetic trends. Their meta‑analysis reveals a complex, uneven distribution of inhibition across taxa, suggesting underlying chloroplast microenvironment drivers and providing a new resource for future photosynthesis improvement efforts.
The study created transgenic Arabidopsis lines enabling inducible plasmodesmal closure via an overactive CALLOSE SYNTHASE3 allele (icals3m) and the C‑terminal domain of PDLP1, independent of pathogen signals. Induced closure triggered stress‑responsive gene expression, elevated salicylic acid levels, and enhanced resistance to Pseudomonas syringae, while also causing starch accumulation, reduced growth, and increased susceptibility to Botrytis cinerea, indicating that plasmodesmal closure itself can activate immune signaling.
Integrative comparative transcriptomics using cultivated and wild rice reveals key regulators of developmental and photosynthetic progression along the rice leaf developmental gradient
Authors: Jathar, V., Vivek, A., Panda, M. K., Daware, A. V., Dwivedi, A., Rani, R., Kumar, S., Ranjan, A.
The study performed comparative gene expression profiling across four rice accessions—from shoot apical meristem to primordia stage P5—to delineate developmental and photosynthetic transitions in leaf development. By integrating differential expression and gene regulatory network analyses, the authors identified stage-specific regulatory events and key transcription factors, such as RDD1, ARID2, and ERF3, especially in the wild rice Oryza australiensis, offering a comprehensive framework for optimizing leaf function.
The study investigated chloroplast retrograde signals that regulate plasmodesmata-mediated intercellular trafficking, identifying heme from the tetrapyrrole biosynthetic pathway as a key modulator. Using Arabidopsis thaliana mutants and Nicotiana benthamiana gene silencing, the authors pinpointed heme‑responsive genes that likely alter plasmodesmata function, linking chloroplast signaling to coordinated plant development and resource allocation.
The authors demonstrate that the WAVE/SCAR complex component BRK1 localizes to plasmodesmata and primary pit fields in Arabidopsis, using a BRK1‑YFP reporter line. BRK1 enrichment coincides with regions of reduced propidium iodide staining and colocalizes with aniline blue‑stained callose, suggesting that ARP2/3‑dependent actin branching contributes to plasmodesmata permeability regulation alongside formin‑mediated linear actin.
The study examined the evolution of plasmodesmata density across an evolutionary gradient of Flaveria species ranging from C3 to C4 photosynthetic types using electron microscopy. It identified two discrete, stepwise increases in plasmodesmata frequency, with a marked enrichment at the mesophyll‑bundle sheath interface in C4-like and C4 species, suggesting that heightened cell‑to‑cell connectivity underpins the development of C4 metabolism.
The study functionally characterizes three tomato CNR/FWL proteins (SlFWL2, SlFWL4, SlFWL5) and demonstrates that SlFWL5 localizes to plasmodesmata, where it regulates leaf size and morphology by promoting cell expansion likely through cell‑to‑cell communication. Gain‑ and loss‑of‑function transgenic tomato lines reveal that SlFWL5 is a key regulator of organ growth via modulation of plasmodesmatal signaling.