Abstract Plant vascular tissues consist of multiple cell types that together coordinate long-distance transport, signaling, and perform diverse metabolic functions. While extensive research uncovered key regulators of vascular patterning and function, the dissection of individual vascular cell types has been hindered by their inaccessibility in planta and the interdependence among the cell types. To overcome these limitations, in vitro transdifferentiation-based approaches have emerged as powerful experimental tools. Here, we provide a comprehensive review of current transdifferentiation strategies used to generate vascular cell types in Arabidopsis thaliana (Arabidopsis), discuss conceptual and technical limitations, and suggest future possibilities and necessity of transdifferentiation-based frameworks to dissect cell-type-specific regulatory programs within complex vascular tissues.
Abstract The circadian clock is an endogenous time-keeping mechanism found in most eukaryotes that integrates external signals to synchronize biological processes with the environment. Circadian and diel rhythms across multiple regulatory layers help coordinate gene expression underlying plant processes such as metabolism, stress responses, and agronomic traits. In the context of a changing environment, a comprehensive understanding of how circadian-mediated regulatory mechanisms can contribute to plant resilient strategies continues to be a priority. In this mini review, we highlight the pleiotropic functions of the rice circadian clock in coordinating diverse processes.
Abstract Sexual reproduction in land plants has diversified over more than 500 million years of evolution. Ferns occupy a key phylogenetic position among land plants because they possess a dominant sporophyte, as in seed plants, while retaining a free-living gametophyte that produces gametes through mitotic divisions, as in bryophytes. This combination of life cycle features provides a useful framework for understanding how reproductive and developmental programs have evolved across land plants. In this review, we summarize current knowledge of fern reproduction, with particular emphasis on the model fern Ceratopteris richardii and the related species C. thalictroides. We focus on four interconnected processes: (1) gametophyte development and the meristem, which functions as a signaling center required for prothallus formation and gametangium positioning; (2) sex determination by antheridiogen, including classical genetic models, hormonal regulation, and recent studies linking meristem identity to sexual fate; (3) gametangium development and gametogenesis, covering antheridium and archegonium formation as well as the differentiation of motile sperm and egg cells; and (4) fertilization and embryogenesis, including gamete interaction, zygotic polarity, and embryonic axis formation. Recent advances in genome sequencing, transformation, genome editing, live imaging, and transcriptomic analyses are beginning to connect the rich morphological literature on ferns with molecular mechanisms. These advances make Ceratopteris a key comparative system for uncovering how reproductive structures, stem cell functions, and embryogenic programs have been conserved, modified, and redeployed during land plant evolution.
Abstract Plasma membrane transporters play an essential role in plant development and all physiological processes. Their activity is tightly controlled by a variety of mechanisms, including the rate of transporter endocytosis. There is evidence that the local membrane environment, in particular the sterol content, influences transporter endocytosis. Here, we analyzed the sucrose transporters StSUT1 (potato) and AtSUC2 (Arabidopsis) transiently expressed in Nicotiana benthamiana epidermal cells. Using live-cell imaging of fluorescent protein fusions combined with extracellular quenching by Trypan Blue, we quantitatively distinguished plasma membrane–localized from internal transporter pools. Pharmacological perturbation of sterols and sphingolipids with methyl-β-cyclodextrin, fenpropimorph and myriocin reduced sucrose transporter abundance at the plasma membrane and decreased uptake of the fluorescent sucrose analogue esculin. In Arabidopsis leaves, methyl-β-cyclodextrin treatment reduced endogenous AtSUC2 protein levels, confirming sterol-dependent regulation in planta. Single-molecule localization microscopy of AtSUC2–reporter constructs revealed its enrichment in ∼50 nm plasma membrane domains, with the localization becoming more homogeneous upon sterol depletion. Together, our results demonstrate that plasma membrane lipid composition modulates sucrose transporter localization and abundance, with likely relevance for the regulation of phloem loading and other membrane proteins.
Abstract GAMETE EXPRESSED PROTEIN1 (GEX1) is a gamete nuclear membrane protein essential for nuclear fusion during sexual reproduction in Arabidopsis thaliana. GEX1 orthologs have been identified in several terrestrial plants. The liverwort Marchantia polymorpha, which uses motile gametes (spermatozoids) for fertilization, possesses a GEX1 homolog, M. polymorpha GEX1 (MpGEX1). In the present study, we investigated the function of MpGEX1 in M. polymorpha. MpGEX1 is expressed during both male and female gametogenesis. During male gametogenesis, MpGEX1 was detected in the nuclear envelope of spermatogenous cells and spermatids but not in mature spermatozoids. In female plants, MpGEX1 was detected in the nuclear envelope of mature egg cells. Mpgex1 mutant strains were not defective in egg or spermatozoid formation. However, Mpgex1 mutant female plants were defective in fertilization when crossed with wild-type spermatozoids. In fertilized egg cells, the male pronucleus, formed from the sperm nucleus, fuses with the female nucleus. However, fertilized Mpgex1 mutant egg cells lack an egg cell-derived nuclear envelope in their male pronuclei. The aberrant pronuclei were elongated or oval and remained separated from female nuclei. Fertilized Mpgex1 mutant egg cells do not undergo zygotic cell divisions. Female-derived mCitrine-MpGEX1 was transiently localized to the male pronucleus shortly after fertilization in females. These results demonstrate that maternally supplied MpGEX1 is essential for male pronucleus formation in M. polymorpha. Our findings reveal a novel role for the plant GEX1 ortholog in fertilization, suggesting the functional diversification of this conserved protein family during the evolution of plant fertilization mechanisms.
