Modern maize stems possess a well-developed vascular bundle system, which is critical for providing mechanical support and lodging resistance. However, characterization of the microanatomical features of vascular bundles and their functional implications in stem mechanics remains challenging, primarily due to technical limitations in high-throughput microanatomical analysis of stem tissues. We thus constructed data sets consisting of over 500,000 maize stem CT images from a maize diversity panel of 383 inbred lines. We evaluated 32 microanatomical phenotypes of maize basal internodes across two environments in different years. By incorporating engineering mechanics parameters, we calculated novel characteristics of the vascular bundles, including the moment of area (MOA) and the polar moment of inertia (PMOI). Through the high-density phenotypic data set, we identified multiple stem microanatomical phenotypes strongly associated with lodging resistance, particularly of vascular bundle mechanical traits. By integrating population genetic profiling, we discovered and confirmed that ZmLSM2 (U6 small nuclear ribonucleoprotein specific Sm-like 2) serves as a key regulator of stem mechanical strength, might function in RNA processing and maturation within vascular stem cells, identifying novel genetic targets for improving maize lodging resistance. This approach demonstrates the value of combining advanced phenotyping with multi-omics analyses for crop improvement. These discoveries will deepen the understanding of plant stem biomechanical principles and provide novel targets for enhancing lodging resistance in crop breeding programs.

Understanding cellular events in three dimensions (3D) is of great importance for the annotation and illustration of biological processes in a contextual way. Imaging techniques based on electron microscopy (EM), such as those derived from scanning electron microscopy (SEM) and transmission electron microscopy (TEM), provide various options to visualize biological samples at scales ranging from cells to macromolecules in situ. Recently, a series of cryogenic techniques has brought EM-based imaging to a new level, enabling specimens to retain their hydrated state throughout the sample preparation and imaging steps, thereby offering a near-native visualization of cellular events. The application of dual-beam focused ion beam (FIB)-SEM to biological samples has enabled high-resolution reconstructions in 3D and streamlined sample preparation workflows for downstream cryo-electron tomography (cryo-ET) imaging. However, applications of these technologies to plant materials are limited due to intrinsic characteristics of plant cells (e.g., non-adhesive growth, large size with a central vacuole, and the presence of cell walls). For the timely application of dual-beam FIB-SEM in three-dimensional subcellular imaging of plant materials, we have recently tested and developed three major workflows with proof-of-concept evidence using developing anthers and in vitro-cultured pollen tubes based on Aquilos 2 Cryo-FIB, including (1) room-temperature FIB-SEM volume imaging, (2) cryo-lamellae preparation from cell suspension culture or high-pressure-frozen organs for cryo-ET imaging, and (3) cryo-FIB-SEM volume imaging, which will facilitate structural studies of plant materials and provide technical guidance for the broader plant cell biology research community.

Cold damage during the seedling and reproductive stages has a pronounced impact on rice development and yield. Although significant progress has been achieved in understanding the physiological and molecular mechanisms underlying rice responses to cold stress, the mechanisms of cold stress perception and adaptation in rice remain mostly unclear. Here, we report the functional study of a cold-responsive gene named LENG, which encodes a plasma membrane-localized leucine-rich repeat (LRR) receptor-like pseudokinase. Gene knockout and overexpression analyses indicated that LENG positively regulates chilling tolerance in rice seedlings. LENG interacts with the plasma membrane-localized cytoplasmic protein kinase, cold-responsive protein kinase 1 (OsCRPK1). Knockout of OsCRPK1 in wild-type and leng mutants elevates rice chilling tolerance, indicating that OsCRPK1 plays a negative role and acts downstream of LENG. In vitro kinase assays revealed that OsCRPK1 is an active protein kinase, but it does not phosphorylate LENG, whereas LENG does not have a kinase activity, but it suppresses the kinase activity of OsCRPK1. In addition, LENG interferes with the interaction between OsCRPK1 and the rice 14-3-3 protein OsGF14d (G-box factor 14-3-3 homolog d), which is known to be a positive regulator of chilling tolerance. The polymorphisms in the promoter and coding region of LENG in japonica and indica rice were correlated with the differential gene expression patterns and chilling tolerance in response to chilling treatment. Taken together, these findings suggest that LENG regulates rice chilling tolerance by modulating the kinase activity of OsCRPK1 and eventually the phosphorylation status of OsGF14d protein. The polymorphisms in LENG provide a selection marker for molecular breeding of rice with improved chilling tolerance.

Genome size, the total amount of DNA content in the cell nucleus, varies greatly among flowering plants. One factor underlying this variation is the environment under which plants evolve. Given this premise, harsh environmental conditions in arid regions may profoundly influence genome evolution. However, the specific impact of aridification on genome size evolution, particularly for African lineages, remains largely unexplored. Here, we investigate linkages between genome size evolution and ecological adaptation using the genus Cyphostemma in the grape family (Vitaceae) as a model. Cyphostemma species exhibit genome size expansion and remarkable morphological traits in arid environments, including succulent stems or leaves and loss of tendrils. Our biogeographic reconstruction, based on substantial taxon sampling (112 of 200 species), reveals that Cyphostemma originated in continental Africa during the late Eocene to Oligocene and has undergone rapid radiation since the middle Miocene, coinciding with intensified aridification and geological activity in eastern Africa. Incorporating extensive data on traits, habitats, genome size, and chromosome numbers, we show that Cyphostemma species with the largest genomes are succulent polyploids restricted to nutrient-rich limestone outcrops. Broad-scale analyses across eudicots further confirm that larger genomes are significantly associated with both succulence and arid habitats. Our findings reveal a strong association between genome size expansion, polyploidy, and adaptive traits, indicating that genome size is a hitherto neglected trait associated with the radiation of succulent plants during the African aridification in the Cenozoic.