Plant and Cell Physiology最新文献

Parasitic plants such as witchweeds transition from complete host dependence below ground to partial autotrophy after emergence, yet the mechanisms coordinating this metabolic shift remain poorly understood. Here, we combine fluorescent dye tracing, metabolite profiling, three-dimensional vascular imaging, tissue-specific transcriptomics, and targeted metabolomics to examine metabolic compartmentalisation in Striga hermonthica and Alectra vogelii. We identify a consistent interruption of host-derived transport at a stem-localised "sink equilibrium zone" (SEqZ) positioned below the first green leaves. This zone coincides with vascular reorganisation, the onset of photosynthesis, and a pronounced reconfiguration of carbohydrate gradients along the parasite axis. Using newly designed metabolite indices, we show that tissues below the SEqZ accumulate raffinose-family oligosaccharides and starch near the haustorium, consistent with strong sink activity and carbon storage, whereas tissues above the SEqZ are enriched in monosaccharides and metabolites associated with photosynthetic activity and growth. Transcriptomic analyses reveal that below-ground tissues preferentially express genes involved in sugar unloading, apoplastic barrier formation, Casparian strip development, and carbohydrate storage, while above-ground tissues activate photosynthesis, circadian regulation, and sugar redistribution pathways. Notably, spatially restricted expression of circadian regulators suggests a localised establishment of temporal control following emergence. Together, these findings support a model in which the SEqZ represents a developmentally defined transition zone where transport, unloading, and metabolic priorities shift to coordinate host-derived and self-fixed carbon through combined anatomical and molecular mechanisms. This framework provides mechanistic insight into trophic mode switching in Striga and Alectra and identifies metabolic features that may be exploited for improved parasitic weed control.

At the core of cell wall integrity (CWI) mechanisms that enable plant cells to coordinate their growth with their cell wall status, lies the transmembrane Malectin-like receptor kinase FERONIA (FER) and its family members. FER itself controls a myriad of plant developmental processes including sexual reproduction, cell growth and morphogenesis, often intersecting with phytohormones-dependent pathways such as abscisic acid (ABA) signaling or plant immunity. Interestingly, FER together with its downstream receptor-like cytoplasmic kinase MARIS (MRI) have been shown to similarly control root hair and rhizoid integrity in the vascular angiosperm Arabidopsis thaliana and the early diverging bryophyte Marchantia polymorpha, respectively. It remains uncertain however whether FER and MRI cooperate beyond tip growth in Marchantia, and which of their functions in Arabidopsis originate from mechanisms established early in land plant evolution. Here, we conducted comparative transcriptomic and proteomic analyses on the M. polymorpha mutant plants, Mpfer-1 and Mpmri-1, alongside their corresponding wild-type accessions. We observed large and significant overlaps between differentially expressed genes and abundant proteins between both mutants. Our multi-omics approach revealed that MpFER and MpMRI largely cooperate to repress transcriptional networks, particularly those associated with plant defense and ABA responses. Nonetheless, our phenotypic analyses showed that MpFER and MpMRI exert distinct functions in response to abiotic stresses such as ABA and salt treatment. Specifically, Mpfer-1, but not Mpmri-1, plants exhibited hypersensitivity to ABA-dependent growth inhibition, indicating that FER's role in negatively regulating ABA-mediated growth responses is conserved between bryophytes and vascular plants.

Myosins are crucial motor proteins associated with the actin cytoskeleton in eukaryotic cells. Structurally, myosins form heteromeric complexes, with smaller light chains such as calmodulin (CaM) bound to isoleucine-glutamine (IQ) domains in the neck region. These interactions facilitate mechano-enzymatic activity. Recently, we reported that Arabidopsis CaM-like (CML) proteins CML13 and CML14 interact with the IQ domains of various proteins and function as myosin VIII light chains. Here, we demonstrate that CaM, CML13, and CML14 specifically bind to the neck region of all 13 Arabidopsis myosin XI isoforms, with some specificity among the CaM/CML-IQ domains. We observed distinct residue preferences within the Myo XI IQ domains for CML13, CML14, and CaM. Recombinant CaM, CML13, and CML14 exhibited calcium-insensitive binding to the IQ domains of myosin XIs. CaM, CML13, and CML14 co-localized to microtubules when co-expressed with MAP65-1-myosin fusion proteins containing the IQ domains of myosin XIs. In addition, in vitro actin motility assays demonstrated that CML13, CML14, and CaM function as myosin XI light chains. A cml13 T-DNA mutant exhibited a shortened primary root phenotype that was complemented by the wild-type CML13 and was similar to that observed in a triple myosin XI mutant (xi-1,2,k). Overall, our data indicate that Arabidopsis CML13 and CML14 are novel myosin XI light chains that likely participate in various myosin XI functions.

Floral bicolor pigmentation in some cultivars of petunia and dahlia is caused by naturally occurring RNA interference (RNAi). In both species, the chalcone synthase gene is highly expressed only in the pigmented regions of bicolor petals. However, the mechanism by which RNAi is specifically induced in the unpigmented regions remains unknown. To elucidate the mechanism underlying this bicolor pattern formation, we analyzed the dicing activity of Dicer-like 4 (DCL4), an essential enzyme in the RNAi pathway. Crude extracts prepared from the pigmented regions strongly inhibited DCL4 activity, whereas this inhibition was abolished when flavonoids were removed from the extracts. Further analyses revealed that the inhibitory activity was attributable to flavonoid aglycons. In vivo dicing activity was detected only in colorless protoplasts prepared from the unpigmented regions of bicolor dahlia petals. These results indicate that in the unpigmented regions, flavonoid aglycons that inhibit DCL4 are not synthesized, allowing RNAi to remain active. In contrast, in the pigmented regions of mature petals, DCL4-and consequently RNAi-is inhibited by flavonoid aglycons, allowing anthocyanin biosynthesis to maintain. Exogenous application experiments of flavonoid aglycons to floral apexes with small flower buds support this conclusion. Therefore, during bicolor flower development, at the stage when petals mature, the clear bicolor pattern is established through a bidirectional feedforward loop involving mutual antagonism between DCL4 and flavonoid aglycons.

CO2-Responsive CCT Protein (CRCT) is a transcription factor that regulates the expression of starch synthesis-related genes, and consequently starch content in the vegetative organs of rice. Two CRCT homologues, AtCRCT1 and AtCRCT2, were identified in the genome of Arabidopsis thaliana. AtCRCT1 and AtCRCT2 were expressed in most organs of the plant, and AtCRCT2 in particular was expressed in their vascular bundles. The expression of these genes was markedly upregulated by sucrose treatment and tended to increase under elevated CO2 condition. The overexpression or knockout of these genes did not have a notable effect on the growth of Arabidopsis. On the other hand, the expression of some starch synthesis-related genes, such as ADP-glucose pyrophosphorylase large subunit3 (AtAPL3) and glucose 6-phosphate/Pi transporter2 (AtGPT2) was significantly upregulated in the overexpression lines. Accordingly, the expression of AtAPL3 and AtGPT2 in the double knockout line was significantly lower than that in wild-type (Col-0) under sucrose treatment. In addition, the starch content of the double knockout line at the end of the night was slightly lower than that of Col-0. Yeast two-hybrid and BiFC analyses demonstrated that both AtCRCT1 and AtCRCT2 interact with Growth Regulation Factor 7, a 14-3-3 protein. These results suggest that AtCRCT1 and AtCRCT2 have similar molecular and physiological functions to CRCT in rice and regulate the expression of some starch synthesis-related genes. However, their effects are limited and cannot markedly affect starch content, unlike CRCT in rice.

Parasitic plants have evolved independently at least a dozen times across angiosperms, yielding some of the most extreme examples of genomic reconfiguration in plants. Comparative analyses of plastid, mitochondrial, and nuclear genomes reveal striking convergence across lineages such as progressive plastid genome reduction with retention of a minimal core gene set, alongside lineage-specific divergences, including unusual mitochondrial genome architectures, rampant horizontal gene transfer, and repeated loss or expansion of nuclear gene families linked to photosynthesis, haustorium development, and host interaction. Expanded sampling largely confirms stepwise plastid genome condensation but also uncovers rare losses of presumed essential genes, novel tRNA retention patterns, and extremes in genome size and base composition. Mitochondrial genomes size largely vary (<60 kb ~ 4 Mb), shaped by repeat proliferation, recombination, and massive acquisition of foreign DNA. Nuclear genomes integrate these organellar changes with structural and regulatory innovations via e.g., polyploidy and repeat-driven evolution, as well as large-scale gene losses. These insights are increasingly translatable to agriculture through predictive weed management and resistance breeding pipelines that combine pre-attachment control, post-attachment defense, and molecular surveillance to slow virulence evolution. The same genomic toolkits including high-quality assemblies, organelle haplotyping, and quantitative diagnostics, can support conservation of non-weedy parasites by refining species boundaries, identifying evolutionarily significant units, and informing IUCN Red List assessments and recovery plans. By bridging fundamental and applied research, parasitic plant genomics is poised to move beyond descriptive cataloguing toward design-based strategies that safeguard crop production while conserving some of the most specialized and ecologically vulnerable plants on Earth.

Artificial pentatricopeptide repeat (PPR) proteins (called as well designer PPR or dPPRs) are customized RNA binding proteins made of tandem repeats of a consensus 35 amino acid motif whose RNA base recognition can be programmed by the use of a two amino acid code. Recently, we designed an artificial PPR protein called dPPRrbcL based on a PPR consensus repeat scaffold flanked by N-terminal and C-terminal domains (NTD and CTD) derived from the native maize protein PPR10, and successfully expressed this protein in Arabidopsis chloroplasts to stabilize a processed 5'-end of rbcL mRNA. While the PPR repeats in dPPRs are expected to confer RNA binding and protection from exoribonuclease, the importance of the N-terminal and C-terminal domains for dPPR in vivo activity remains unknown. Here, we used functional complementation assays in Arabidopsis using truncated versions of dPPRrbcL to examine the contribution of the NTD and CTD to rbcL mRNA stabilization in chloroplasts. The results showed that the NTD and CTD are not required for the in vivo stabilization of the processed 5' end of rbcL mRNA by dPPRrbcL but the NTD likely protects a few nucleotides at the 5'-end of the RNA sequence bound by the PPR motifs against the action of exoribonucleases. These discoveries indicate that a PPR repeat scaffold itself is sufficient to efficiently stabilize processed RNAs in chloroplasts.