Plant and Cell Physiology最新文献

The AAA+ ATPase CDC48A is a central regulator of proteostasis in plants, functioning through interactions with a diverse set of cofactors. Among these, the plant-specific ubiquitin regulatory X (UBX) domain-containing proteins (PUX) are key adaptors that direct CDC48A to specific substrates and pathways. The molecular basis of PUX-CDC48A interactions remains incompletely understood. Here, we combine structural, biophysical, and computational approaches to dissect the binding modes of representative PUX proteins from different subfamilies in Arabidopsis thaliana. Although all PUX proteins tested exhibit low micromolar affinities for CDC48A, they form unexpectedly stable complexes, suggesting additional mechanisms of interaction. We identify two distinct strategies for complex stabilisation, producing different dynamic features. One relies on combining two weak associations: PUX5 employs a SHP-UBX module that engages the CDC48A N domain at two proximal sites, whereas PUX2 uses a SHP motif and a distant PUB domain to engage the N- and C-termini of CDC48A. In contrast, PUX6, PUX7, and PUX9 allosterically stabilise the association between their UBX domain and the CDC48A N domain. These multi-pronged strategies likely enable durable yet reversible associations, facilitating fine-tuned competitive regulation of CDC48A activity across diverse cellular contexts. Our findings provide a mechanistic framework for understanding how PUX proteins achieve specificity, stability, and regulatory flexibility in directing CDC48A function.

Embryogenesis is an essential process involving a series of formative cell divisions that contribute to establishing the plant's body axis. In many dicotyledons, the asymmetric cell division of the zygote gives rise to two daughter cells, which develop into two distinct cell lineages. In contrast, the fate of the two daughter cells and their contribution to the body axis formation remains poorly understood in the monocots. To address this question, we developed a method for three-dimensional imaging of early rice embryos. Our observations demonstrated that both an egg cell and two synergids are polarized prior to fertilization and are anchored to the micropylar end of the ovule via a cell wall-like structure stained with SR2200. Upon fertilization, the zygote undergoes an asymmetric cell division with a ventrally tilted division plane. The following cell divisions are not strictly synchronized between the apical and basal lineages, exhibiting non-stereotypic patterns up to the globular stage of embryogenesis. Furthermore, we examined the role of auxin signaling in rice embryogenesis using the auxin response sensor DR5rev::NLS-3xVENUS. The reporter activity was first detected at the center of the globular embryos, and subsequently extended along the apical-basal axis as embryogenesis progressed. Our results highlight the importance of the progressive establishment of the body axes within cell populations during early embryogenesis.

Phosphate deficiency reduces nodule formation in various legumes, which hinders nitrogen fixation and crop yield. We previously showed that phosphate deficiency reduces nodule formation by activating the autoregulation of nodulation (AON) pathway. We also observed that some genetic components of the AON pathway contain Phosphate Starvation Response 1 binding site cis-regulatory elements in their promoter regions, which are recognized by the Phosphate Starvation Response 1 transcription factor. This evidence led us to hypothesize that host plant phosphate levels regulate the expression of genes essential for forming nodules through a PHR-Like protein. In the present study, we provide evidence supporting the participation of PvPHR-Like 7 (PvPHR-L7) in regulating nodule formation in Phaseolus vulgaris. Modulation of PvPHR-L7's expression by RNA interference and overexpression suggested that this transcription factor may control the expression of crucial symbiotic genes involved in nodule development in P. vulgaris. An RT-qPCR analysis revealed that the expression of PvPHR-L7, PvNIN, and PvTML is regulated in accordingly to the plant host Pi levels. Transactivation assays in Nicotiana benthamiana and P. vulgaris transgenic roots indicate that PvPHR-L7 can upregulate the expression of PvNIN and PvTML in the absence of rhizobia. In contrast, PvPHR-L7 downregulates the expression of PvNIN under symbiotic conditions with rhizobia. The data presented shed light on the potential role that PvPHR-L7 plays in the root nodule symbiosis.

Dioecious plants often exhibit dimorphism in morphology, physiology, and environmental adaptation. As a dioecious gymnosperm, Taxus is well known for its ornamental and ecological value. However, the sexual dimorphism in the responses of Taxus mairei to fungal infection remains unclear. In the present study, we investigated the effect of sex on the responses of T. mairei to S01, a fungus belonging to the Aspergillus genus, using untargeted metabolomic analysis. Although there is no significant difference in the contents of eight analyzed flavonoid monomers between female and male T. mairei plants under normal condition, a significant difference emerges under fungal infection. We identified 15 members of the abscisic acid insensitive3/viviparous1 (RAV)-like gene subfamily in the T. mairei genome. Subsequently, a RAV-like transcription factor (TF) gene, RAV-like 9, which is responsive to S01 infection, was identified to be involved in flavonoid metabolism based on Pearson's correlation analysis. To identify the genome-wide binding sites of RAV-like 9, DNA affinity purification sequencing (DAP-seq) was performed, yielding 3993 overlapping peaks. Motif enrichment analysis identified several de novo motifs, providing new insights into RAV TF recognition sites. After searching the peak pool, two flavonoid biosynthesis-related target genes were detected: ANS (ctg19199_gene.2) and IRL1 (ctg9900_gene.5). Quantitative reverse transcription polymerase chain reaction analysis confirmed the differential expression of ANS and IRL1 between female and male T. mairei under S01 infection. Our data suggest that RAV-like 9 may play an important regulatory role in sex-specific responses of flavonoid biosynthesis to fungal infection by targeting the ANS and IRL1 genes.

Salinity stress severely impairs seed germination in plants. In this study, we identified MsWRKY75, a salt-responsive WRKY transcription factor from alfalfa (Medicago sativa L.), and characterized its role in modulating abscisic acid (ABA) signaling to regulate seed germination under salinity stress. Phylogenetic and structural analyses revealed that MsWRKY75, homologous to Medicago truncatula MtWRKY75, contains a conserved WRKYGQK motif and a C2H2-type zinc finger domain. Subcellular localization confirmed its nuclear localization, while yeast assays demonstrated transcriptional activation activity, supporting its function as a transcription factor. Overexpression of MsWRKY75 in Arabidopsis and M. truncatula led to enhanced suppression of seed germination under both salinity and ABA treatments in a dose-dependent manner. Interestingly, MsWRKY75 did not affect ABA biosynthesis or catabolism, but specifically upregulated core components of the ABA signaling pathway. Quantitative real-time-PCR analysis revealed strong induction of MtABI5 a key repressor of seed germination and its upstream receptor MtPYL4 in MsWRKY75-overexpressing lines. Yeast one-hybrid, dual-luciferase, and chromatin immunoprecipitation assays demonstrated that MsWRKY75 directly binds to the W-box cis-element within the MtABI5 promoter, activating its transcription. Mutation of the W-box motif abolished this interaction, confirming its essential role in transcriptional activation. Together, these results establish MsWRKY75 as a negative regulator of seed germination under salinity stress, acting through direct enhancement of ABA signaling. This study provides new mechanistic insights into ABA-mediated stress responses and identifies MsWRKY75 as a promising candidate for improving stress resilience through genetic engineering in legume crops.

Various aspects of Japanese morning glory (Ipomoea nil) petals, such as color, pattern, shape, flower opening time, and senescence, have been extensively studied. To facilitate such studies, transcriptome data were collected from flower petals at 3-h intervals over 3.5 days; the data were collected 72 h before and 12 h after flower opening, accounting for 29 time points. This dataset serves as a comprehensive foundation for analyzing transcriptomic dynamics across a wide spectrum of developmental stages, ranging from closed buds to fully opened flowers and subsequently senescing petals. Gene ontology analysis highlighted substantial transcriptomic changes between the preflowering and postflowering stages. The short-interval sampling facilitated the identification of 805 genes exhibiting circadian rhythmicity. Further transcriptome analysis provided insights into petal development, senescence, and coloration. The expression patterns of cell division marker genes indicated that cell division practically stops at ~48 h before the flower opens. Furthermore, the increased expression of genes encoding transporters for sugars, amino acids, nucleic acids, and autophagy-related genes was observed post-flower opening, indicating the translocation of nutrients from senescing petal cells to other developing tissues. Correlations were identified between the temporal expression patterns of three transcriptional regulators and distinct sets of structural genes within the anthocyanin biosynthesis pathway. These findings suggest that each regulator plays a unique role in activating specific structural genes. The temporal transcriptome data and interactive database (https://ipomoeanil.nibb.ac.jp/fpkm/) offer valuable insights into gene expression dynamics, periodicity, and correlations and provide a crucial resource for further research on I. nil and other plant species.