June-Sik Kim

The photosynthetic flagellate Euglena gracilis is a unique evolutionary lineage characterized by a chimeric cellular organization resulting from secondary endosymbiosis. 1-3 This species exhibits h...

As a staple food for half the world’s population, rice is an important dietary source of magnesium (Mg), an essential mineral for human health. Enhanced Mg accumulation in rice grains has also been linked to eating quality. However, the mechanisms underlying Mg transport to the grains remains poorly understood. Here, we report that OsMGR2, a member belonging to Magnesium Release (MGR) family, is required for Mg accumulation in rice grains. OsMGR2 encodes a plasma membrane-localized transporter that mediates Mg efflux. OsMGR2 is constitutively and highly expressed in the stele tissues of roots, the phloem region of both enlarged and diffused vascular bundles in nodes, and the ovular vascular trace of caryopses. Knockout of this gene results in decreased root-to-shoot translocation and altered distribution of Mg to different organs; less Mg is allocated to the second newest leaf with high Mg requirement for active photosynthesis. The osmgr2 mutants exhibit decreased Mg accumulation in the grain, which are smaller, lighter, and shriveled, but show increased accumulation in the husk. The eating quality of the mutant grains is significantly decreased compared with the wild-type rice. These results indicate that OsMGR2 plays multiple roles within the rice; facilitating the root-to-shoot Mg translocation, mediating phloem-to-xylem Mg transfer at nodes for preferential distribution to the most active leaf, and exporting Mg from maternal vascular tissues of the caryopsis to the grains, processes essential for grain development and eating quality in rice.

Drought tolerance in crops often involves trade‐offs between water conservation, growth and reproduction. Understanding how water‐saving strategies are implemented at physiological and metabolic levels remains critical for improving crop performance under water‐limited conditions. Here, we characterise a wheat TILLING mutant, WS1, that exhibits enhanced survival under drought stress. WS1 showed reduced stomatal conductance and transpiration, together with increased carbon isotope discrimination, consistent with reduced water loss. Despite these traits, WS1 displayed weak stomatal responses to exogenous abscisic acid (ABA), indicating that its water‐saving behaviour is not primarily explained by canonical ABA signalling. Metabolomic analyses revealed substantial accumulation of proline and changes in nitrogen and carbon metabolism, suggesting a shift toward a survival‐oriented metabolic state. Phosphoproteomic profiling further identified distinct phosphorylation patterns associated with energy‐related signalling components, including proteins linked to SnRK1 pathways. These molecular features likely reflect an altered energy‐sensing and regulatory state rather than direct causal drivers of the phenotype. Notably, WS1 exhibited reduced fertility, indicating a trade‐off between survival and reproductive investment. Together, our results suggest that WS1 adopts a water‐saving drought survival phenotype characterised by coordinated physiological and metabolic reprogramming, providing a framework for understanding survival‐oriented drought responses and resource allocation strategies in wheat.

Pre-mRNA splicing is essential for eukaryotic gene expression and is achieved through the accurate recognition of exon–intron boundaries. Although nonconventional introns, which do not follow the conventional GT-AG splicing rule, have been identified in several species, these introns are typically rare in any given genome. Here, we demonstrate the widespread occurrence of nonconventional introns (71.8% of all introns) in the Euglena agilis genome and identify consensus motifs at these nonconventional exon–intron boundaries. We assessed the splicing efficiency of nonconventional introns and variants with point mutations via genomic knock-in within the second exon of Glucan synthase-like 2 in Euglena gracilis and genetically defined the sequence signature (5′-N ₃ CDG-/-CH′GN _5–6 |R _exon -3′) required for their proper splicing. This signature is present in 61.2% of all nonconventional introns detected in the E. agilis genome. Accordingly, we present a noncanonical splicing code for Euglena introns, highlighting the global coexistence of dual splicing rules for conventional and nonconventional introns.

Plant cell culture has multiple applications in biotechnology and horticulture, from plant propagation to the production of high-value biomolecules. However, the interplay between cellular diversity and ambient conditions influences the metabolism of cultured tissues; understanding these factors in detail will inform efforts to optimize culture conditions. This study presents multiomics datasets from callus cultures of tobacco (Nicotiana tabacum), rice (Oryza sativa), and two bamboo species (Phyllostachys nigra and P. bambusoides). Over four weeks, calli were cultured under continuous moisture without airflow or gradually reduced ambient moisture with airflow. For each sample, gene expression was profiled with high-throughput RNA sequencing, 442 metabolites were measured using liquid chromatography (LC) with triple-quadrupole mass spectrometry (LC–QqQMS), and 31 phytohormones were quantified using ultra-performance LC coupled with a tandem quadrupole mass spectrometer equipped with an electrospray interface (UPLC-ESI-qMS/MS) and ultra-high-performance LC–orbitrap MS (UHPLC-Orbitrap MS). These datasets highlight the impact of airflow on callus cultures, revealing differences between and within species, and provide a comprehensive resource to explore the physiology of callus growth.

Plant cell culture has multiple applications in biotechnology and horticulture, from plant propagation to the production of high-value biomolecules. However, the interplay between cellular diversity and ambient conditions influences the metabolism of cultured tissues; understanding these factors in detail will inform efforts to optimize culture conditions. This study presents multiomics datasets from callus cultures of tobacco ( Nicotiana tabacum ), rice ( Oryza sativa ), and two bamboo species ( Phyllostachys nigra and P. bambusoides ). Over four weeks, calli were cultured under continuous moisture without airflow or gradually reduced ambient moisture with airflow. For each sample, gene expression was profiled with high-throughput RNA sequencing, 442 metabolites were measured using liquid chromatography (LC) with triple-quadrupole mass spectrometry (LC–QqQMS), and 31 phytohormones were quantified using ultra-performance LC coupled with a tandem quadrupole mass spectrometer equipped with an electrospray interface (UPLC-ESI-qMS/MS) and ultra-high-performance LC– orbitrap MS (UHPLC-Orbitrap MS). These datasets highlight the impact of airflow on callus cultures, revealing differences between and within species, and provide a comprehensive resource to explore the physiology of callus growth.

Drought and cold represent distinct types of abiotic stress, each initiating unique primary signaling pathways in response to dehydration and temperature changes, respectively. However, a convergence at the gene regulatory level is observed where a common set of stress-responsive genes is activated to mitigate the impacts of both stresses. In this review, we explore these intricate regulatory networks, illustrating how plants coordinate distinct stress signals into a collective transcriptional strategy. We delve into the molecular mechanisms of stress perception, stress signaling, and the activation of gene regulatory pathways, with a focus on insights gained from model species. By elucidating both the shared and distinct aspects of plant responses to drought and cold, we provide insight into the adaptive strategies of plants, paving the way for the engineering of stress-resilient crop varieties that can withstand a changing climate.

Transgene‐free genome editing based on clustered regularly interspaced short palindromic repeats (CRISPR) technology is key to achieving genetic engineering in microalgae for basic research and industrial applications. Euglena gracilis , a unicellular phytoflagellate microalga, is a promising biomaterial for foods, feeds, cosmetics and biofuels. However, methods for the genetic manipulation of E. gracilis are still limited. Here, we developed a high‐efficiency, transgene‐free genome editing method for E. gracilis using Lachnospiraceae bacterium CRISPR‐associated protein 12a (LbCas12a) ribonucleoprotein (RNP) complex, which complements the previously established Cas9 RNP‐based method. Through the direct delivery of LbCas12a‐containing RNPs, our method reached mutagenesis rates of approximately 77.2–94.5% at two different E. gracilis target genes, Glucan synthase‐like 2 ( EgGSL2 ) and a phytoene synthase gene ( EgcrtB ). Moreover, in addition to targeted mutagenesis, we demonstrated efficient knock‐in and base editing at the target site using LbCas12a‐based RNPs with a single‐stranded DNA donor template in E. gracilis. This study extends the genetic engineering capabilities of Euglena to accelerate its basic use for research and engineering for bioproduction.

Globally, bread wheat (Triticum aestivum) is one of the most important staple foods; when exposed to drought, wheat yields decline. Although much research has been performed to generate higher yield wheat cultivars, there have been few studies on improving end-product quality under drought stress, even though wheat is processed into flour to produce so many foods, such as bread, noodles, pancakes, cakes, and cookies. Recently, wheat cultivation has been affected by severe drought caused by global climate change. In previous studies, seed shrinkage was observed in wheat exposed to continuous drought stress during seed development. In this study, we investigated how progressive drought stress affected seed development by metabolomic and transcriptomic analyses. Metabolite profiling revealed the drought-sensitive line reduced accumulation of proline and sugar compared with the water-saving, drought-tolerant transgenic line overexpressing the abscisic acid receptor TaPYL4 under drought conditions in spikelets with developing seeds. Meanwhile, the expressions of genes involved in translation, starch biosynthesis, and proline and arginine biosynthesis was downregulated in the drought-sensitive line. These findings suggest that seed shrinkage, exemplifying a deficiency in endosperm, arose from the hindered biosynthesis of crucial components including seed storage proteins, starch, amino acids, and sugars, ultimately leading to their inadequate accumulation within spikelets. Water-saving drought tolerant traits of wheat would aid in supporting seed formation under drought conditions.