Journal of Plant Research最新文献

Orchids are obligately dependent on orchid mycorrhizal fungi (OMF) for nutrition, growth, and establishment. The degree of mycorrhizal specificity varies, from generalists associating with several fungi to specialists relying on a few species. Many leafless epiphytic orchids specifically associate with Ceratobasidiaceae fungi. However, the mycorrhizal associates and specificity of Taeniophyllum marianense, a leafless epiphytic orchid native to the remote island of Guam, remain unknown. To address this knowledge gap, we investigated 189 seedling and mature individuals of T. marianense growing on 26 host tree species across 10 sites in Guam. OMF were identified using fungal-specific primers targeting Ceratobasidiaceae, Serendipitaceae, Tulasnellaceae, and general Basidiomycota. Sequences were grouped into operational taxonomic units (OTUs) based on 97% similarity. T. marianense in Guam associated with a diversity of OMF, including five Tulasnellaceae, six Ceratobasidiaceae, and four Serendipitaceae OTUs. Two Tulasnellaceae OTUs (TU1 and TU2) were the most dominant, comprising 64.6% of fungal sequences and occurring consistently across seedling and mature orchids from different host tree species and habitats, suggesting their role as primary mycorrhizal associates. In contrast, Ceratobasidiaceae and Serendipitaceae were less common and may play minor or opportunistic roles. The mycorrhizal capacity of TU1 and TU2 isolates was confirmed in vitro, where both strains significantly promoted seed germination and protocorm development. While other leafless epiphytic orchids typically associate with Ceratobasidiaceae, T. marianense in Guam specifically associates with Tulasnellaceae fungi closely related to globally distributed species. These findings suggest that mycorrhizal specialization may persist in island ecosystems through flexible associations with widespread, locally available fungal associates.

Triploid plants are usually sterile or produce non-viable seeds, but may produce fruits. This study examined the morphological and reproductive characteristics of triploid Passiflora cincinnata Masters, with a focus on fruit and seed production. Triploid plants were obtained through in vitro cultivation of the endosperm via somatic embryogenesis, whereas diploid plants were raised through seed germination. Diploid and triploid plants were confirmed by flow cytometry and cytogenetic analyses. Cross-pollination and self-pollination yielded, on average, 18 fruits per plant in the cytotype diploid, while triploids produced only 6 fruits. Diploid plants have more uniform fruits, while triploid plants showed variations in size. Seeds with malformations or absence of zygotic embryos and endosperm were observed in triploid cytotypes, while remaining below 1.5% in diploid cytotypes. It was observed that the highest germination rate of 80% occurred in seeds of the diploid cytotype, compared to 53.3% in triploids. The seedlings from the cross between diploid plants contained 3.29 pg of nuclear DNA and a chromosome number of 2n = 2x = 18, while the seedlings from the cross between triploid plants had progeny with 3.37 pg of nuclear DNA and variable chromosomes numbers, of 2n = 19 (2n + 1), 2n = 15 (2n - 3), and 2n = 16 (2n - 2) chromosomes confirming aneuploidy in the progeny. Stomatal analysis showed that diploid plants displayed the highest stomatal density, whereas triploid and aneuploid plants had the greatest length and width of stomata. The density and width of pavement epidermal cells varied among cytotypes. Meiotic disturbances in triploid plants cause phenotypic alterations in the progeny, resulting in delayed vegetative development, low vigor, non-uniform germination, and death during the juvenile phase. The genetic material of aneuploids is a resource for gene mapping, enabling the modification or production of new cultivars with economically relevant phenotypes.

Species delimitation methods based on macromorphology are often limited by phenotypic plasticity in plants. Fourier Transform near-infrared spectroscopy (FT-NIR) provides a promising alternative as a non-destructive technique that measures molecular vibrations (overtone and combination bands of C-H, N-H, and O-H bonds) from plant tissue exposed to near-infrared light (780-2,500 nm). We applied FT-NIR to the taxonomically challenging Scaly clade of Microgramma ferns (94 samples, eight species), including dimorphic and monomorphic taxa, to evaluate its diagnostic potential. Using multivariate models and cross-validation, we achieved 81-100% average identification accuracy. Well-defined species (e.g., M. percussa) reached 100% accuracy, while morphologically overlapping taxa showed lower accuracy, likely due to hybridization, introgression, or cryptic variation. Dimorphic species exhibited higher intraspecific spectral variability and lower accuracy linked to differences between fertile/sterile fronds than monomorphic species. FT-NIR proves effective as a complementary tool for fern systematics, elucidating species limits and diversity patterns. Further studies should address how hybridization, introgression, and indumentum affect spectral data.

Plastid ribosomal proteins (PRPs) are core components of the plastid translational machinery, playing indispensable roles in chloroplast biogenesis and plant growth. While the functions of some PRPs in rice have been characterized, the biological role of the plastid 50 S ribosomal protein L5 (PRPL5) remains unclear. Here, we characterize the function of Albino Lethal Seedling 2 (ALS2), encoding the PRPL5, in early chloroplast development. CRISPR/Cas9-mediated knockout of ALS2 resulted in seedling-lethal albino phenotypes, significantly reduced chlorophyll concentration, and disrupted chloroplast ultrastructure. ALS2 is highly expressed in rice leaves and its protein is localized in rice chloroplasts. Further analysis of gene expression revealed that nuclear and plastid genes participating in chloroplast development showed notable alterations in their expression in the als2 mutants. Notably, als2 mutants accumulated reactive oxygen species (ROS), particularly superoxide anions, which was accompanied by enhanced expression of ROS-scavenging genes and chlorophyll degradation genes. These findings demonstrate that ALS2 is essential for early chloroplast development in rice.

In mutualistic symbiosis between plants and bacteria, the abundance and composition of symbiotic bacterial groups in the soil microbiota can be important for plant growth. Here, we focused on the nitrogen-fixing mutualism between Lotus japonicus and nodule bacteria to investigate whether and how much the abundance of symbiotic rhizobia in the soil microbiota of natural environments contributes to variations in host plant growth. An inoculation experiment of soil microbiota revealed extensive variations in plant growth phenotypes, even between microhabitats. We found that the local presence of L. japonicus and the relative abundance of Mesorhizobium bacteria showed positive correlations with plant growth supported by both 16S amplicon sequencing and shotgun metagenome analyses. Among bacteria investigated, the abundance of Mesorhizobium was most strongly associated with plant growth phenotypes, supporting its role as the primary symbiotic rhizobia in natural environments. Given the specificity and the selectivity of plants for favorable rhizobia, legume-rhizobia interactions could trigger a positive plant-soil feedback that enriches favorable rhizobia into the soil surrounding legume plant habitats.

Glycine betaine (GB), a key osmoprotectant in plants, alleviates abiotic stress through osmotic adjustment and reactive oxygen species (ROS) scavenging. Although betaine aldehyde dehydrogenase (BADH) catalyzes GB biosynthesis and enhances salinity tolerance in crops such as rice and maize, its role in waterlogging adaptation remains unclear. A putative BADH gene, HfBADH1, was cloned from waterlogging-treated daylily (Hemerocallis spp.) 'Autumn Red'. HfBADH1 expression increased 6.8-fold under waterlogging and 8.9-fold under salinity. Notably, HfBADH1 expression was repressed by abscisic acid (ABA), in contrast with typical stress-responsive genes. In addition, the activities of BADH and aldehyde dehydrogenase (ALDH) correlated with waterlogging tolerance among different daylily cultivars. Overexpression of HfBADH1 in Arabidopsis thaliana under the CaMV35S promoter resulted in 2.4-fold higher BADH activity and twofold higher ALDH activity than in wild-type plants. The transgenic lines exhibited enhanced tolerance to both salinity and waterlogging. Stress responses were evaluated by antioxidant and anaerobic respiration enzyme activities, and physiological indices including malondialdehyde (MDA) levels and chlorophyll content. The observed stress tolerance in transgenic A.thaliana suggested that BADH overexpression helps stabilize cellular structures and scavenges ROS. The increase in ALDH activity indicated that HfBADH1 overexpression may facilitate aldehyde oxidation, supporting adaptation to hypoxic conditions induced by waterlogging. This study is the first to link BADH overexpression to dual stress resilience, highlighting its combined enzymatic roles in GB biosynthesis and aldehyde detoxification. The ABA-independent regulatory pattern provides insight into noncanonical stress adaptation and suggests new strategies for engineering crops tolerant to saline and flood-prone environments.