Mutsumi Watanabe

Parasitic plants rarely attack themselves, suggesting the existence of a kin-avoidance mechanism. In the root parasitic plant Phtheirospermum japonicum , prehaustorium formation is triggered by host-secreted haustorium-inducing factors (HIFs), but it is unresponsive to its own exudates. Here we report the identification of the spontaneous prehaustorium 1 ( spoh1 ) mutant, which forms prehaustoria without external host signals. spoh1 harbors a point mutation in the gene encoding uridine diphosphate–glucosyltransferase UGT72B1, an enzyme that glucosylates and thereby inactivates phenolic HIFs. PjUGT72B1 has a different substrate specificity than its ortholog of the host Arabidopsis . Introduction of PjUGT72B1 into Arabidopsis reduced prehaustorium induction activity, indicating that UGT72B1 regulates haustorium induction by hosts. Our findings suggest that Orobanchaceae hemiparasitic plants have evolved kin-avoidance mechanisms through the glucosylation of endogenous HIFs.

Regulation of the phenylpropanoid pathway is critical for plant development and defense. This research investigates the transcriptional control of six Phenylalanine Ammonia-Lyase (PAL) gene homologs identified in the mulberry genome. A comprehensive in silico pipeline was employed to analyze the promoter architecture of these genes. Using the MEME suite, we identified three statistically significant conserved motifs within the 2000 bp upstream region. Subsequent TF binding prediction with FootprintDB for these motifs implicated the TCP, NAC, AP2/ERF, B3, and BBR-BPC families as potential regulators. A parallel analysis with PlantRegMap highlighted a high density of binding sites for the BBR-BPC and AP2/ERF families in the core promoter regions. A comparative analysis showed a weak correlation between the databases, underscoring the necessity of a multi-faceted predictive approach. Transcriptomic profiling under chitosan-induced conditions validated our in silico framework, suggesting the involvement of these TF families. Specifically, the data support NAC083 as a putative transcriptional activator and suggest a repressive function for members of the AP2/ERF and BBR-BPC families, providing a robust, experimentally supported model of PAL regulation.

Exposure to UV-B radiation, an intrinsic component of solar light, is detrimental to all living organisms as chromophore units of DNA, RNA and proteins readily absorb high-energy photons. Indirect damage to the same molecules and lipids is mediated by elevated reactive oxygen species (ROS) levels, a side effect of exposure to UV-B stress. To protect themselves from UV-B radiation, plants produce phytochemical sunscreens, among which flavonoids have shown to be particularly effective. The core aglycone of flavonoid molecules is subjected to chemical decoration, such as glycosylation and acylation, further improving sunscreen properties. In particular, acylation, which adds a phenolic ring to flavonoid molecules, enhances the spectral absorption of UV-A and UV-B rays, providing to this class of compounds exceptional shielding power. In this study, we comprehensively analyzed the responses to UV-B radiation in four Brassicaceae species, including Arabidopsis thaliana, Brassica napus, Brassica oleracea, and Brassica rapa. Our study revealed a complete reprogramming of the central metabolic pathway in response to UV-B radiation characterized by increased production of functional precursors of specialized metabolites with UV-B shielding properties, indicating a targeted effort of plant metabolism to provide increased protection. The analysis of specialized metabolites and transcripts revealed the activation of the phenylpropanoid–acetate pathway, leading to the production of specific classes of flavonoids and a cross-species increase in phenylacylated-flavonoid glucosides with synapoyl glycoside decorations. Interestingly, our analysis also revealed that acyltransferase genes of the class of serine carboxypeptidase-like (SCPLs) proteins are costitutively expressed, but downregulated in response to UV-B radiation, possibly independently of the ELONGATED HYPOCOTYL 5 (HY5) signaling pathway.

SUMMARY: Senescence is a highly regulated process driven by developmental age and environmental factors. Although leaf senescence is accelerated by nitrogen (N) deficiency, the underlying physiological and molecular mechanisms are largely unknown. Here, we reveal that BBX14, a previously uncharacterized BBX‐type transcription factor in Arabidopsis, is crucial for N starvation‐induced leaf senescence. We find that inhibiting BBX14 by artificial miRNA (amiRNA) accelerates senescence during N starvation and in darkness, while BBX14 overexpression (BBX14‐OX) delays it, identifying BBX14 as a negative regulator of N starvation‐ and dark‐induced senescence. During N starvation, nitrate and amino acids like glutamic acid, glutamine, aspartic acid, and asparagine were highly retained in BBX14‐OX leaves compared to the wild type. Transcriptome analysis showed a large number of senescence‐associated genes (SAGs) to be differentially expressed between BBX14‐OX and wild‐type plants, including ETHYLENE INSENSITIVE3 (EIN3) which regulates N signaling and leaf senescence. Chromatin immunoprecipitation (ChIP) showed that BBX14 directly regulates EIN3 transcription. Furthermore, we revealed the upstream transcriptional cascade of BBX14. By yeast one‐hybrid screen and ChIP, we found that MYB44, a stress‐responsive MYB transcription factor, directly binds to the promoter of BBX14 and activates its expression. In addition, Phytochrome Interacting Factor 4 (PIF4) binds to the promoter of BBX14 to repress BBX14 transcription. Thus, BBX14 functions as a negative regulator of N starvation‐induced senescence through EIN3 and is directly regulated by PIF4 and MYB44.

Sulfur deficiency-induced proteins SDI1 and SDI2 play a fundamental role in sulfur homeostasis under sulfate-deprived conditions (−S) by downregulating glucosinolates. Here, we identified that besides glucosinolate regulation under –S, SDI1 downregulates another sulfur pool, the S-rich 2S seed storage proteins in Arabidopsis (Arabidopsis thaliana) seeds. We identified that MYB28 directly regulates 2S seed storage proteins by binding to the At2S4 promoter. We also showed that SDI1 downregulates 2S seed storage proteins by forming a ternary protein complex with MYB28 and MYC2, another transcription factor involved in the regulation of seed storage proteins. These findings have significant implications for the understanding of plant responses to sulfur deficiency.

Many solanaceous crops are an important part of the human daily diet. Fruit polyphenolics are plant specialized metabolites that are recognized for their human health benefits and their defensive role against plant abiotic and biotic stressors. Flavonoids and chlorogenates are the major polyphenolic compounds found in solanaceous fruits that vary in quantity, physiological function, and structural diversity among and within plant species. Despite their biological significance, the elucidation of metabolic shifts of polyphenols during fruit ripening in different fruit tissues, has not yet been well-characterized in solanaceous crops, especially at a cross-species and cross-cultivar level. Here, we performed a cross-species comparison of fruit-metabolomics to elucidate the metabolic regulation of fruit polyphenolics from three representative crops of Solanaceae (tomato, eggplant, and pepper), and a cross-cultivar comparison among different pepper cultivars (Capsicum annuum cv.) using liquid chromatography-mass spectrometry (LC-MS). We observed a metabolic trade-off between hydroxycinnamates and flavonoids in pungent pepper and anthocyanin-type pepper cultivars and identified metabolic signatures of fruit polyphenolics in each species from each different tissue-type and fruit ripening stage. Our results provide additional information for metabolomics-assisted crop improvement of solanaceous fruits towards their improved nutritive properties and enhanced stress tolerance.

The purpose of this study was to determine the ideal coronal alignment under dynamic conditions after open-wedge high tibial osteotomy (OWHTO). It was hypothesised that, although the classical target alignment was based on experimental evidence, it would demonstrate biomechanical validity.

The capacity for optimising grain yield depends largely on the timing of senescence and the processes underlying efficient remobilisation and cycling of nutrients from source tissues to the developing grain. This study describes how metabolism is adjusted during senescence in response to varying nitrogen application rates after anthesis. A comprehensive metabolite analysis was performed in field-grown Avalon/Cadenza using segregating doubled haploid wheat genotypes having contrasting traits relating to timing of the onset of senescence. Correlative matrices of metabolites and yield parameters determined the metabolic networks that underlie these phenotypes, and were helpful for identifying unique metabolites that are indicative of timing of senescence. They also revealed robust correlations between steady increases in hexose levels, a late senescence phenotype and high straw yield associated with low N fertiliser levels. Tryptophan, cis-aconitate, phosphate and 1-kestose demonstrated strong perturbations in response to nitrogen availability and progression towards developmental senescence. A comprehensive metabolic map of wheat leaf primary metabolites yielded a cumulative readout of processes that occur during developmental ripening and contribute to grain filling in plants with differential senescence timing.