Plant Biotechnology最新文献

Cassava is a globally important food source. Given the increasing frequency of climate change-induced drought, enhancing the drought resilience of cassava is paramount. Chemical priming can bolster tolerance to stress factors. We previously determined that pretreatment with low concentrations of ethanol enhances abiotic stress tolerance in Arabidopsis, tomato, and cassava. Nevertheless, the efficacy of ethanol treatment in complex natural settings remains to be fully explored. In this study, we assessed the impact of ethanol treatment on cassava under varying light photon flux densities (PFDs) and drought conditions. We observed that drought tolerance was enhanced by ethanol pretreatment at high (∼400 µmol photons m^-2 s^-1) and medium (∼60 µmol photons m^-2 s^-1) light PFDs but not under low light PFD (∼4 µmol photons m^-2 s^-1). Ethanol pretreatment under high and medium light PFDs promoted stomatal closure and drought avoidance, thereby preserving higher water content in plant tissues. Furthermore, ethanol pretreatment under these PFDs upregulated expressions of genes associated with ABA signaling and heat shock proteins (HSPs) relative to water pretreatment. In addition, starch accumulation in leaves was observed under all light PFDs with ethanol pretreatment. We hypothesize that ethanol pretreatment at light PFDs exceeding 60 µmol photons m^-2 s^-1 facilitates ethanol-mediated drought avoidance in cassava by activating at least three pathways: 1) ABA signaling, 2) protein folding-related response via triggering of the HSP/chaperone network, and 3) alterations in sugar and starch metabolism. Our findings support the application of optimal light PFDs to enhance the benefits of ethanol-induced drought avoidance in cassava.

Quantitative trait loci involved in reducing high temperature injury during grain filling were investigated using fifty-four lines of the chromosome segment substitution lines (CSSLs) of the indica cultivar Kasalath in the japonica cultivar Nipponbare background. The ratio of chalky seeds was examined when they were ripened under the high-temperature conditions. Among these lines, SL13 seeds showed an obvious trait of alleviating injury. In SL13, a part of the chromosome 3 was substituted with the Kasalath genome, which contained a locus of this trait locus. Fine mapping of this locus using the progenies obtained by crossing SL13 with Nipponbare narrowed it down to a region of 3.36-3.81 Mb on chromosome 3. This region included the OsSUT1 gene encoding sucrose transporter 1. The Nipponbare OsSUT1 contained 19-nucleotide insertion in the promoter region, suggesting that this diversity might affect the transcription level of this gene. The progeny plants of SL13 containing the Kasalath OsSUT1, which had a significantly higher expression level of this gene, obviously reduced the high-temperature injury. Transformants carrying the Kasalath OsSUT1 gene showed significant alleviation in the high-temperature injury during grain filling. Our results indicate that OsSUT1 is a major factor consisting of the locus involved in reducing the high temperature injury in SL13. These results suggest that the enhanced function of OsSUT1 provides sufficient carbon assimilates to immature seeds even under high temperature conditions, leading to normal seed formation.

Hedysari Radix, a significant Chinese herbal medicine from Northwest China's arid region, is renowned for its unique tonic effects in traditional Chinese medicine practices. This plant, a member of the Leguminosae family, forms a symbiotic relationship with nitrogen-fixing rhizobia. However, the Hedysarum polybotrys-rhizobium symbiotic system remains underexplored. The root nodule structure of H. polybotrys was examined using an optical microscope (OM). This examination revealed that its root nodules consist of meristematic zone, infection zone, nitrogen fixation zone, and senescence zone, arranged from top to bottom. This structure suggests that the root nodules of H. polybotrys belong to the indeterminate nodule category. In the fields of transmission electron microscopy (TEM) and fields emission scanning electron microscopy (FESEM), significant differences were observed between infected and un-infected cells. Rhizobium, identified via 16S rRNA technology and classified as the genus Mesorhizobium through phylogenetic analysis. Reinoculation of rhizobium into H. polybotrys seedlings resulted in nodule formation on the roots. Notably, inoculated plants exhibited a considerable increase in nodule number, leaf count, leaf length, aboveground height, aboveground fresh weight, root length, and root diameter compared to uninoculated controls, demonstrating that rhizobium inoculation enhances plant growth.

Gentians are important ornamental plants, and gentian cultivars have been actively bred for decades. However, limited genetic resources are currently available for breeding; therefore, artificial mutagenesis has been applied to generate mutants. In this study, we developed a simple and efficient regeneration-mediated method for ion beam mutagenesis in the Japanese gentian hybrid cultivar 'Albireo' (Gentiana scabra × G. triflora). Carbon and neon ion species were tested. Effect of ion beam irradiation on callus formation from leaves was initially evaluated. Tissue culture was then continued, adventitious shoots were induced from calli, and many regenerated plants were obtained. These plants were cultivated until flowering, and two cultivated lines exhibiting a double-flowered phenotype were identified from leaves exposed to 9 and 12 Gy of neon ion beam irradiation among approximately 200 individuals. We analyzed one line derived from irradiation with 9 Gy of neon ions, named Ne9Gy#34, in detail. The agamous gene (AG1), previously identified as the gene responsible for the double-flower phenotype in gentians, was not amplified in the G. scabra allele by genomic polymerase chain reaction. Moreover, next-generation sequencing also indicated that the reads were mapped to the genomic region of the G. triflora AG1 but not to that of G. scabra, suggesting that the deletion of G. scabra AG1 led to the double-flowered phenotype. Ne9Gy#34 also exhibited increased flower size, suggesting additional mutations in genes other than AG1. In summary, the developed regeneration-mediated method represents a promising approach for inducing gentian mutagenesis and efficiently producing novel traits in this plant.

Papaya (Carica papaya L.), a tropical plant belonging to the Caricaceae family, is widely cultivated in tropical and subtropical countries. Young leaves grow from the stem tips, petioles elongate, and leaf color changes from light green to dark green during development. Papaya leaves are used as therapeutic agents in folk medicine and potential functional food materials; however, the specific associations between the leaf development stage and functional components of papaya remain unknown. Therefore, in this study, we aimed to conduct a non-targeted analysis of the four developmental stages of papaya leaves via liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry. Specifically, we focused on carpaine derivatives and γ-aminobutyric acid that have attracted attention in the Japanese functional food industry. Carpaine derivatives were abundant in young leaves; however, their levels decreased with increasing leaf maturity. In contrast, γ-aminobutyric acid levels increased with increasing leaf maturity. Multivariate analyses revealed that the metabolites changed more significantly during the transition to the dark green phase than during the transition from the early yellow green to bright green phase. Additionally, proteolytic activity was evaluated using casein as a substrate. Proteolytic activity decreased with increasing leaf maturity. In conclusion, our findings suggest that leaves at different developmental stages should be selected based on their functional components and intended application.

Nuclear staining using fluorescent dyes is crucial for cytological studies in plants. However, few fluorescent dyes are suitable for live-cell imaging of the nucleus. Here, we demonstrate that dimidium bromide (DimBr), a commercially available fluorescent dye, can be used to stain the nucleus (nucleolus and nucleoplasm) in living plant cells. DimBr emits peak fluorescence at 600 nm at an excitation wavelength of 525 nm, making it well suited for use with green fluorescent protein. DimBr staining can be used in various plant species and allows time-lapse observation of the nucleus. Therefore, DimBr can be used to visualize the nucleus in living plant cells, making it a valuable tool for plant cell biology.

Pink-pigmented facultative methylotrophs (PPFMs), encompassing the genera Methylobacterium and Methylorubrum, can utilize reduced one-carbon compounds such as methanol, methylamine, formaldehyde, and formate as carbon and energy sources. They are commonly associated with plants, particularly on leaf surfaces (phyllosphere), where their methylotrophic metabolism offers a significant adaptive advantage over other bacterial species. These genera hold quite diverse species with unique phenotypes. Many studies report plant growth-promoting activity of the genera due to their ability to produce plant hormones and help plants acquire nutrients. Also, the ecology of the genera that enables them to survive in such a harsh environment exposed to ultraviolet light, fluctuating temperature and humidity, and limited nutrients is the key to understanding their diversity, functions, and adaptations supported by their genotypes. In this review, we summarize their taxonomy diversified by their genotypes and niches, functions involved in plant growth promotion and survival in the phyllosphere, and practical application of the bacteria for agricultural purposes.

A diverse range of microbes have been observed to coexist in plant roots in the field, among which arbuscular mycorrhizal fungi (AMFs) are universal and have recently been shown to be of two types: one belonging to the subphylum Glomeromycotina (G-AMF) and the other to the subphylum Mucoromycotina (M-AMF). These two types of mycorrhizal fungi are known to co-occur in roots. This is because, in addition to the morphological evidence, diverse ribosomal RNA (rRNA) gene sequences, including those of G-AMF, are detected in mycorrhizae colonized with M-AMF. However, it is difficult to physically distinguish between these AMFs, and amplification bias of G-AMF and M-AMF by PCR has hampered analysis of the detailed symbiotic behaviour of both AMFs. In this study, we isolated a single vesicle of lipid-accumulating AMF in the root and sequenced its rRNA gene by PCR using uniquely designed primers with reduced amplification bias. Notably, G-AMF and M-AMF rRNA gene sequences were detected in one vesicle. These results suggest new avenues for mycorrhizal research on the overlooked morphology of AMF vesicles and their mode of genetic co-occurrence of G-AMF and M-AMF.

Farmyard manure (FYM)-a mixture of animal excreta and plant residues-remains an important nutrient resource for lowland rice production in sub-Saharan Africa (SSA). However, the underlying mechanism of FYM in altering microbiological communities and supplying nutrients for rice production remains poorly understood. Hence, this study aimed to elucidate the effects of FYM application on N fixation and the diazotroph communities in the nutrient-deficient lowlands of SSA. Soil samples from three farmers' fields in Madagascar were incubated with ¹⁵N₂ gas for 1 month to assess their N fixation capacity. The plots in each field were subjected to the following fertilizer conditions: control (no fertilizer inputs) or continuous application of FYM or mineral fertilizer for previous 4 years. One field with a high N fixation capacity was selected to analyze the nitrogenase (nifH) and 16S rRNA genes in the rhizosphere. The continuous application of FYM significantly increased the N-fixation capacity of the soil compared with one-time or no FYM applications, particularly in fields where FYM was highly effective on rice yield improvement. Continuous FYM application also significantly increased the relative abundance of nifH gene sequences close to iron-oxidizing bacteria (Family Gallionellaceae) in the rhizosphere, whereas this change did not occur with the continuous application of mineral fertilizer. These results imply that continuous FYM application enhances N fixation capacity via changes in the diazotroph communities. The high abundance of diazotrophs related to the oxidation-reduction process of iron may be associated with the iron-rich soils in the region.