Sang Heon Kim

The taxonomic classification of the tribe Veroniceae (Plantaginaceae) has been debated, particularly regarding the generic delimitation of Pseudolysimachion Opiz. Traditionally treated as an indepe...

The genus Pseudolysimachion (Plantaginaceae) is currently considered a subgenus of Veronica, though its independent status is still debated. In Korea, Veronica subgenus Pseudolysimachion is diverse, including widespread Veronica longifolia (formerly Pseudolysimachion longifolium) and endemic Veronica pusanensis (formerly Pseudolysimachion pusanensis), both valuable for horticulture. Despite chloroplast genome utility in plant phylogenetics and breeding, complete chloroplast genome data for these key species were absent. To address this gap, we sequenced, assembled, and characterized the complete chloroplast genomes of V. longifolia and V. pusanensis. The complete chloroplast genomes of V. longifolia (152,237 bp) and V. pusanensis (152,250 bp) displayed typical quadripartite structures and encoded 133 genes (88 protein-coding, 37 tRNA, 8 rRNA). Phylogenetic analysis strongly supported the monophyly of the Veronica subgenus Pseudolysimachion clade, which is nested deeply within the genus Veronica. Our findings provide essential genomic resources that clarify phylogenetic relationships within the subgenus and contribute significantly to the broader taxonomic resolution of the tribe Veroniceae. These results firmly establish the taxonomic positions of the Korean endemic species, V. longifolia and V. pusanensis, and offer crucial genomic insights into speciation patterns and evolutionary trends within the genus, thereby supporting future plant breeding and germplasm utilization strategies.

Pseudolysimachion pyrethrinum var. gasanensis (Gasan spike speedwell) is a valuable Korean endemic variety with significant horticultural potential. Despite its morphological distinctiveness, its taxonomic status and evolutionary position have remained a subject of debate. In this study, we assembled and characterized the first complete chloroplast (cp) genome of P. pyrethrinum var. gasanensis using high-throughput sequencing. The complete plastome is 152,251 bp in length, exhibiting a typical quadripartite structure with a large single-copy (LSC) region (83,191 bp), a small single-copy (SSC) region (17,690 bp), and two inverted repeats (IRs) (25,685 bp each). The genome contains 133 genes, including 88 protein-coding, 37 tRNA, and 8 rRNA genes. Genomic analysis identified 42 simple sequence repeat (SSR) units across 38 distinct loci, predominantly mononucleotide A/T motifs, which serve as potential molecular markers for variety-level identification. Selective pressure analysis revealed that the majority of protein-coding genes are under strong purifying selection (Ka/Ks < 1.0), emphasizing the evolutionary stability of the plastome. Comparative analysis of IR boundaries using IRscope revealed a high degree of structural conservation among Pseudolysimachion species, with minor variations at the junction sites. Phylogenetic analysis based on 18 complete plastomes strongly supported the monophyly of the genus Pseudolysimachion (Bootstrap = 100%) and placed P. pyrethrinum var. gasanensis as a sister to the European P. spicatum. These genomic resources provide a foundational tool for the molecular breeding, systematic conservation, and sustainable utilization of this endemic variety, while offering clarity to its taxonomic classification within the tribe Veroniceae.

Climate change necessitates a deeper understanding of plant tolerance mechanisms to dual water stresses. This study investigated the distinct physiological and genetic responses of Longleaf Speedwell (Pseudolysimachion longifolium) to drought and waterlogging using RNA-Seq. Physiological data showed a rapid and comparable reduction in photosynthetic efficiency after one week and a reduction in biomass under both stresses after two weeks. However, transcriptomic analysis revealed fundamentally distinct strategies: Drought induced a massive transcriptional response characterized by the strong upregulation of defense and stress-tolerance pathways and the severe shutdown of growth-related metabolism. In contrast, waterlogging triggered a constrained hypoxic response, prioritizing energy conservation by downregulating synthesis processes and activating ethylene signaling. The reliability of the RNA-Seq data was confirmed by qRT-PCR, which also crucially identified Alcohol dehydrogenase (ADH), Ethylene Responsive Factor (ERF), and Peroxidase (POD) as common candidate genes highly induced under both drought and waterlogging conditions, suggesting a shared genetic module for general water stress tolerance. These findings provide valuable insights into the adaptation mechanisms of non-model plants to complex environmental changes.

Climate change necessitates a deeper understanding of plant tolerance mechanisms to dual water stresses. This study investigated the distinct physiological and genetic responses of Longleaf Speedwell (Pseudolysimachion longifolium) to drought and waterlogging using RNA-Seq. Physiological data showed a rapid and comparable reduction in photosynthetic efficiency after one week and biomass under both stresses after two weeks. However, transcriptomic analysis revealed fundamentally distinct strategies: Drought induced a massive transcriptional upheaval (5 times more DEGs), characterized by the upregulation of defense pathways (e.g., Phenylpropanoid biosynthesis) and the severe shutdown of growth-related metabolism (e.g., Ribosome, Photosynthesis). In contrast, waterlogging triggered a constrained hypoxic response, prioritizing energy conservation by downregulating synthesis processes (Nitrogen, Arginine biosynthesis) and activating ethylene signaling. The reliability of the RNA-Seq data was confirmed by qRT-PCR, which also crucially identified Alcohol dehydrogenase (ADH), Ethylene Responsive Factor (ERF), and Peroxidase (POD) as common candidate genes highly induced under both drought and waterlogging conditions, suggesting a generalized role in broad-spectrum water stress tolerance. These findings provide critical molecular evidence demonstrating the divergent and specific adaptive strategies of P. longifolium to different water regimes and highlight ADH, ERF, and POD as promising targets for engineering broad-spectrum water stress tolerance.

This study analyzed the seed germination characteristics and physiological responses of five Korean Veronica species (V. daurica, V. nakaiana, V. kiusiana var. glabrifolia, V. pusanensis, and V. pyrethrina) under salinity stress. Preliminary experiments on five Veronica species using various NaCl concentrations revealed that treatment with 150 mM NaCl almost completely inhibited seed germination, whereas treatment with >50 mM NaCl significantly decreased seed germination rate and index. Therefore, this study focused on the effects of treatment with 0, 50, and 100 mM NaCl for 7 days on the germination rate, germination index, germination energy, germination vigor index, water content, fresh weight, dry weight, and root length of the plants. When treated with 100 mM NaCl, most species had few survivors after 5 days, even if germination had occurred. Almost all parameters significantly decreased with increasing NaCl concentration. Especially, fresh weight and water content decreased with increasing NaCl concentration, while dry weight did not show a significant response to NaCl concentration, suggesting that salinity stress inhibited water uptake, which is crucial for seed germination. Hormonal analysis revealed the presence of indole-3-acetic acid (IAA) and abscisic acid (ABA) and the absence of gibberellic acid. Most species showed no significant changes in IAA and ABA levels with varying NaCl concentrations. However, V. pusanensis showed significantly increased ABA levels with increasing NaCl concentration, and V. daurica showed significantly higher IAA levels at 100 mM NaCl than at other NaCl concentrations. This study demonstrates that salt stress negatively affects Veronica seed germination, with varying intensities among species.

There is an increasing demand for low-maintenance public garden models, and environmental stress on plants due to climate change is growing. As a result, the demand for developing new plant varieties based on native species for use in gardens in response to climate change has increased significantly. Many plants in the Poaceae family are applied for various purposes, including food crops, fodder grasses, ornamental plants, and medicinal plants. Additionally, native plants provide economic and ecological benefits, making them advantageous for use in gardens. However, there are some difficulties in Poaceae breeding studies and the utilization of wild native plants for breeding. Model plants can be utilized in breeding studies of Poaceae plant species. In this study, to identify Korean native Poaceae species with the potential for use not only as garden materials but also as model plants for breeding research in response to climate change, candidate species were selected from the Korean Plant Names Index (KPNI). A total of three Korean native plants in the Poaceae family, including Brachypodium sylvaticum, Setaria viridis, and Zoysia japonica, were selected, and their properties and genome information were compared with the existing representative model plants, Arabidopsis thaliana and Brachypodium distachyon. The current research status of B. sylvaticum, S. viridis, and Z. japonica has been summarized, and the genome size and other characteristics of these model plants have been compared and discussed. As a result, both A. thaliana (2n = 2x = 10) and B. distachyon (2n = 2x = 10) are annual C₃ plants, but B. sylvaticum (2n = 2x = 18) is a perennial C₃ plant, and S. viridis (2n = 2x = 18) is an annual C₄ plant. Thus, B. sylvaticum and S. viridis can be utilized as model plants for perennial C₃ plants and annual C₄ plants, respectively. Z. japonica (2n = 4x = 40) is a perennial C₄ plant, but it can be unsuitable as a model plant because it is an allotetraploid. The application of these newly selected candidate plants in breeding research can build a foundation for breeding native Poaceae plants in Korea in the new climate regime.

There are increasing needs for models of public garden with low-maintenance, and environmental stress to plant due to climate change is growing. Therefore, the demand for developing new plant varieties based on native plants as garden materials against climate change has increased fairly. Many plants in the family Poaceae are applied for various purposes such as food crops, fodder grasses, ornamental plants, or medical plants. Also, native plants have some economic and ecological benefits, and the utilization of native plants is positive in a garden. However, there are some difficulties in Poaceae breeding researches and utilization of wild native plants for breeding. To overcome these problems, model plants can be utilized in breeding researches of Poaceae plant species. In this study, to explore the possibility of utilizing Korean native Poaceae plants as model plants and for breeding new cultivars, the candidate species were selected from the Korean Plant Names Index (KPNI). A total of 3 Korean native plants in the family Poaceae including Brachypodium sylvaticum, Setaria viridis, and Zoysia japonica were selected, and their properties and their genome information were compared with the representative model plants, Arabidopsis thaliana and Brachypodium distachyon. The modern research status of B. sylvaticum, S. viridis and Z. japonica has been summarized, and the genome size, life cycle, and other characteristics of these model plants have been compared and discussed. Application of these newly selected candidate plants in breeding research would build a foundation for breeding of native Poaceae plants in Korea against the new climate regime.

Salinity stress is a critical abiotic stress that reduces crop productivity. Durum wheat (Triticum turgidum ssp. durum) is an essential cereal in Tunisia, a country threatened by salinity stress. In this study, 26 accessions of Tunisian durum wheat were subjected to salinity stress induced by 500 mM NaCl, and their salinity tolerance was evaluated by examining phenotypic parameters and calculating the salinity tolerance trait index and salinity tolerance index. Furthermore, two Tunisian durum wheat cultivars, namely ‘Om Rabia’ (salinity-tolerant) and ‘Mahmoudi’ (salinity-susceptible), were subjected to RNA sequencing (RNA-Seq) analysis, and single-nucleotide polymorphisms (SNPs) were detected from the RNA-Seq data of these two cultivars. The impacts of all SNP variants on genes were predicted, and 157 candidate SNP primer pairs were designed preferentially using high-impact transcripts. Following confirmation using polymerase chain reaction (PCR) analysis of data from ‘Om Rabia’ and ‘Mahmoudi’, 17 SNP markers were developed and applied to assess the remaining 26 Tunisian durum wheat lines. Three developed SNP markers (KUCMB_TRIDC7AG078450.6_12, KUCMB_TRIDC2BG061830.1_05, and KUCMB_TRIDC2BG061830.1_08) showed PCR bands only in salinity-tolerant lines but not in moderately tolerant or susceptible lines. Therefore, the developed SNP markers may be used to screen the salinity tolerance of various durum wheat accessions.