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.
Phylogenomic challenges in polyploid-rich lineages: Insights from paralog processing and reticulation methods using the complex genus Packera (Asteraceae: Senecioneae)
Authors: Moore-Pollard, E. R., Ellestad, P., Mandel, J.
The study examined how polyploidy, hybridization, and incomplete lineage sorting affect phylogenetic reconstructions in the genus Packera, evaluating several published paralog‑processing pipelines. Results showed that the choice of orthology and paralog handling methods markedly altered tree topology, time‑calibrated phylogenies, biogeographic histories, and detection of ancient reticulation, underscoring the need for careful methodological selection alongside comprehensive taxon sampling.
Arabidopsis lines with modified ascorbate concentrations reveal a link between ascorbate and auxin biosynthesis
Authors: Fenech, M., Zulian, V., Moya-Cuevas, J., Arnaud, D., Morilla, I., Smirnoff, N., Botella, M. A., Stepanova, A. N., Alonso, J. M., Martin-Pizarro, C., Amorim-Silva, V.
The study used Arabidopsis thaliana mutants with low (vtc2, vtc4) and high (vtc2/OE-VTC2) ascorbate levels to examine how ascorbate concentration affects gene expression and cellular homeostasis. Transcriptomic analysis revealed that altered ascorbate levels modulate defense and stress pathways, and that TAA1/TAR2‑mediated auxin biosynthesis is required for coping with elevated ascorbate in a light‑dependent manner.
The study investigated sugar loading mechanisms in the giant duckweed Spirodela polyrhiza and found that it lacks typical sucrose transporter genes and does not use active apoplastic or symplastic loading, instead employing passive symplastic phloem loading characterized by uniform plasmodesmata density. Hormone‑induced reduction of plasmodesmata permeability lowered sucrose levels in phloem exudate, pinpointing plasmodesmata regulation as a key factor in carbon export for this monocot species.