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Herbivorous insects and pathogens cause severe damage to rice tissues, affecting yield and grain quality. Damaged cells trigger downstream defense responses through various signals. Extracellular ATP (eATP), a signaling molecule released during mechanical cell damage, is considered a constitutive damage-associated molecular pattern (DAMP), which is crucial for initiating plant defense responses. Thus, understanding how rice plants cope with DAMPs such as eATP is essential. Here, we found that exogenous ATP affected rice growth and development, cell wall composition, chloroplast development, and cell death. Subsequent global transcriptome analysis revealed that several pathways were involved in the eATP response, including genes related to cell surface receptors, cell wall organization, chlorophyll biosynthesis, heat and temperature stimulation, epigenetic regulation, and reactive oxygen species metabolism. Cell surface receptors, including members of the lectin receptor-like kinases (LecRKs), were found to participate in the eATP response. We further investigated ATP-induced genes in T-DNA activation mutants of OsLecRKs, demonstrating their involvement in eATP signaling in rice. This study confirms a DAMP-mediated transcriptional response in plants and provides novel candidates for advancing resistant rice breeding against insect herbivores and pathogens. 

Abstract We present the first chromosome-level genome assembly and annotation for the genus Cuscuta, a twining and leafless parasitic plant of the morning glory family (Convolvulaceae). C. campestris, the study species, is a widely studied model parasite, due in part to its worldwide occurrence as a weed of agricultural and natural plant communities. The species has served as a model parasite for studies of parasite biology, haustorium development, growth responses to chemical and light stimuli, gene content and expression, horizontal gene transfer, and interspecies RNA movement and has a recently developed transformation system. The 505 Mb (1C) genome is assembled into 31 chromosomes and supports annotation of 47,199 protein-coding genes, 214 small RNA loci (including 146 haustoria-specific miRNAs), and 3,238 interspecies mobile mRNA loci. C. campestris is a recent tetraploid with a high retention of duplicated genes and chromosomes, with less than 8% nucleotide divergence between homoeologous chromosomes. We also show that transformation of C. campestris with the RUBY marker system allows visualization of transformed Cuscuta-derived fluorescent mobile molecules that have entered the host stem. This genome, with an associated genome browser and BLAST server, will be of value for scientists performing fundamental research in a wide range of molecular, developmental, population, and evolutionary biology, as well as serve as a research tool for studying interspecies mobile molecules, generating genetic markers for species and genotype identification, and developing highly specific herbicides. 

Two plants connected via a Cuscuta bridge exchange rapid systemic calcium, electric, and reactive oxygen species signals, suggesting that Cuscuta may have beneficial effects to host plants. 

Cuscuta spp. are obligate parasites that connect to host vascular tissue using a haustorium. In addition to water, nutrients, and metabolites, a large number of mRNAs are bidirectionally exchanged between Cuscuta spp. and their hosts. This trans-specific movement of mRNAs raises questions about whether these molecules function in the recipient species. To address the possibility that mobile mRNAs are ultimately translated, we built upon recent studies that demonstrate a role for transfer RNA (tRNA)-like structures (TLSs) in enhancing mRNA systemic movement. C. campestris was grown on Arabidopsis that expressed a β-glucuronidase (GUS) reporter transgene either alone or in GUS-tRNA fusions. Histochemical staining revealed localization in tissue of C. campestris grown on Arabidopsis with GUS-tRNA fusions, but not in C. campestris grown on Arabidopsis with GUS alone. This corresponded with detection of GUS transcripts in Cuscuta on Arabidopsis with GUS-tRNA, but not in C. campestris on Arabidopsis with GUS alone. Similar results were obtained with Arabidopsis host plants expressing the same constructs containing an endoplasmic reticulum localization signal. In C. campestris, GUS activity was localized in the companion cells or phloem parenchyma cells adjacent to sieve tubes. We conclude that host-derived GUS mRNAs are translated in C. campestris and that the TLS fusion enhances RNA mobility in the host-parasite interactions. 

Summary Cuscuta campestris, a stem parasitic plant, has served as a valuable model plant for the exploration of plant–plant interactions and molecular trafficking. However, a major barrier toC. campestrisresearch is that a method to generate stable transgenic plants has not yet been developed.Here, we describe the development of aCuscutatransformation protocol using various reporter genes (GFP, GUS, or RUBY) and morphogenic genes (CcWUS2andCcGRF/GIF), leading to a robust protocol forAgrobacterium‐mediatedC. campestristransformation.The stably transformed and regenerated RUBYC. campestrisplants produced haustoria, the signature organ of parasitic plants, and these were functional in forming host attachments. The locations of T‐DNA integration in the parasite genome were confirmed through TAIL‐PCR. TransformedC. campestrisalso produced flowers and viable transgenic seeds exhibiting betalain pigment, providing proof of germline transmission of the RUBY transgene. Furthermore, RUBY is not only a useful selectable marker for theAgrobacterium‐mediated transformation, but may also provide insight into the movement of molecules fromC. campestristo the host during parasitism.Thus, the protocol for transformation ofC. campestrisreported here overcomes a major obstacle toCuscutaresearch and opens new possibilities for studying parasitic plants and their interactions with hosts. 

Societal Impact Statement Rafflesiais a genus of parasitic plants with the largest flowers in the world, unique to the threatened forest habitats of tropical Asia. Here, we report on genes that are active (the transcriptome) inRafflesiaseeds as part of a larger effort to understandRafflesia.Rafflesiahas never been grown successfully outside of its native range. Consequently, seed banking is not yet possible, precluding a critical management strategy for conservation. The study ofRafflesiaseed biology is a critical step to improve its cultivation, which will educate the public about unique species and the importance of conserving their habitats. SummaryRafflesiais of great interest as one of the only two plants known to have completely lost its chloroplast genome.Rafflesiais a holoparasite and an endophyte that lives inside the tissues of its host, a tropical grape vine (Tetrastigma), emerging only to bloom—with the largest flower of any plant. Here, we report the firstRafflesiaseed transcriptome and compare it with those of other plants to deepen our understanding of its extraordinary life history.We assembled a transcriptome from RNA extracted from seeds of the Philippine endemicRafflesia speciosaand compared this with those of other plants, includingArabidopsis, parasitic plantsStrigaandCuscuta, and the mycoheterotrophic orchidAnoectochilus.Genetic and metabolic seed pathways inRafflesiawere generally similar to the other plant species. However, there were some notable exceptions. We found evidence of horizontal transfer of a gene potentially involved in circumventing host defenses. Moreover, we identified a possible convergence among parasitic plants becauseRafflesia,Striga, andCuscutashared important similarities. We were unable to find evidence of genes involved in mycorrhizal symbiosis, suggesting that mycoheterotrophy is unlikely to play a role inRafflesiaparasitism.To date, ex situ propagation ofRafflesiaby seed has been mostly unsuccessful. Our research is a bold step forward in understanding the fundamentals ofRafflesiaseed biology that will inform the continued propagation and seed‐banking efforts concerning this recalcitrant plant. We discuss our findings in the broader context of the conservation of a genus in peril.