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Panax ginseng C.A.Mey. (Araliaceae) cultivation suffers from the inability to cultivate the same fields continuously for long durations due to replant failure. The main cause of replant failure is considered to be the annual change in the soil microbial flora, especially the invasion and settlement of pathogenic microorganisms of soil-borne diseases. We analyzed the soil bacterial and fungal flora and inter-annual changes in their composition over 5 years in ginseng cultivation fields on Daikonshima Island, Shimane Prefecture of Western Japan by DNA metabarcoding using next-generation sequencing. Bacteria such as Sphingomonas sp., Bacillus sp., and Betaproteobacteria and the fungus Mortierella sp. were consistently detected throughout the cultivation period. The inter-annual compositional changes of the bacterial flora, especially two members of the family Burkholderiaceae, one member of the phylum Actinobacteria, one member of the genus Candidatus Koribacter, and one member of the genus Sphingomonas, corresponded to the cultivation period, whereas those of the fungal flora showed random changes, suggesting that the growth of ginseng may be greatly affected by changes in the bacterial flora. Therefore, a greater understanding of the bacterial flora could provide valuable information for the cultivation of ginseng. The absence of pathogenic microorganisms associated with soil-borne diseases, which have been reported as causative agents of the main diseases of ginseng, in all soil sampling sites throughout the entire cultivation period in this study proves, for the first time, that traditional cultivation management employing empirical methods and chemical control is an effective approach to control these pathogens. Therefore, the DNA metabarcoding of the bacterial flora could provide valuable information for cultivation management, specifically in detecting and controlling soil-borne pathogens responsible for ongoing cultivation damage in long-term cultivation of medicinal plants.

Microbiota are a major component of agroecosystems. Root microbiota, which inhabit the inside and surface of plant roots, play a significant role in plant growth and health. As next-generation sequencing technology allows the capture of microbial profiles without culturing the microbes, profiling of plant microbiota has become a staple tool in plant science and agriculture. Here, we have developed a novel high-throughput method based on a two-step PCR amplification protocol, involving DNA extraction using magnetic beads and PCR purification using exonuclease, for 16S rRNA gene amplicon sequencing of plant root microbiota. This method reduces sample handling and captures microbial diversity comparable to that obtained by the standard method. We found that using a buffer with magnetic beads enabled efficient extraction of microbial DNA directly from plant roots. In addition, we demonstrated that purification using exonuclease before the second PCR step enabled the capture of higher degrees of microbial diversity, thus allowing for the detection of minor bacteria compared with the purification using magnetic beads in this step. Our method offers a simple and high-throughput solution for maintaining the quality of plant root microbial community profiling.

Agrobacterium-mediated transformation represents a key innovation for plant breeding and is routinely used in research and applied biology. However, for several species, the efficacy of transformation is limited. In this study, we discovered that oxicam-type nonsteroidal anti-inflammatory drugs (NSAIDs), including tenoxicam (TNX), enhance the efficiency of Agrobacterium-mediated transient transformation in the model species Arabidopsis thaliana via leaf infiltration and can be successfully applied in analyses of the subcellular localisation of fluorescent fusion proteins. TNX acts as an inhibitor of plant immune responses and lacks similar transient transformation efficiency in a dde2/ein2/pad4/sid2 quadruple mutant background, thereby indicating that TNX increases the efficiency of Agrobacterium infection via a transient shutdown of the immune system mediated by jasmonic acid, ethylene, and salicylic acid signalling. In addition, we found that TNX enhances the efficiency of stable transformation in crops of agricultural and economic importance, such as Jatropha and maize, indicating that TNX can enhance the integration of exogenous DNA into the plant genome via an increased introduction of DNA into plant cells. Given that treatment with oxicam compounds is simple, cost effective, and has broad utility, we anticipate that this discovery will contribute to accelerating genome-editing technologies in plants.

Monocarpic plants have a single reproductive phase, in which their longevity is developmentally programmed by molecular networks. In the reproductive phase of Arabidopsis thaliana, the inflorescence meristem (IM) maintains a central pool of stem cells and produces a limited number of flower primordia, which result in seed formation and the death of the whole plant. In this study, we observed morphological changes in the IM at cellular and intracellular resolutions until the end of the plant life cycle. We observed four biological events during the periods from 1 week after bolting (WAB) till the death of stem cells: (1) the gradual reduction in the size of the IM, (2) the dynamic vacuolation of IM cells, (3) the loss of the expression of the stem cell determinant WUSCHEL (WUS), and (4) the upregulation of the programmed cell death marker BIFUNCTIONAL NUCLEASE1 (BFN1) in association with the death of stem cells. These results indicate that the stem cell population gradually decreases in IM during plant aging and eventually is fully terminated. We further show that the expression of WUS became undetectable in IM at 3 WAB prior to the loss of CLAVATA3 (CLV3) expression at 5 WAB; CLV3 is a negative regulator of WUS. Moreover, clv3 plants showed delayed loss of WUS and lived 6 weeks longer compared with wild-type plants. These results indicated that the prolonged expression of CLV3 at 4–5 WAB may be a safeguard that inhibits the reactivation of WUS and promotes plant death. Finally, through transcriptome analysis, we determined that reactive oxygen species (ROS) are involved in the control of plant longevity. Our work presents a morphological and physiological framework for the regulation of plant longevity in Arabidopsis.

Parasitic plants infect other plants by forming haustoria, specialized multicellular organs consisting of several cell types, each of which has unique morphological features and physiological roles associated with parasitism. Understanding the spatial organization of cell types is, therefore, of great importance in elucidating the functions of haustoria. Here, we report a three-dimensional (3-D) reconstruction of haustoria from two Orobanchaceae species, the obligate parasite Striga hermonthica infecting rice (Oryza sativa) and the facultative parasite Phtheirospermum japonicum infecting Arabidopsis (Arabidopsis thaliana). In addition, field-emission scanning electron microscopy observation revealed the presence of various cell types in haustoria. Our images reveal the spatial arrangements of multiple cell types inside haustoria and their interaction with host roots. The 3-D internal structures of haustoria highlight differences between the two parasites, particularly at the xylem connection site with the host. Our study provides cellular and structural insights into haustoria of S. hermonthica and P. japonicum and lays the foundation for understanding haustorium function.

Parasitic plants infect other plants by forming haustoria, specialized multicellular organs consisting of several cell types each of which has unique morphological features and physiological roles associated with parasitism. Understanding the spatial organization of cell types is, therefore, of great importance in elucidating the functions of haustoria. Here, we report a three-dimensional (3-D) reconstruction of haustoria from two Orobanchaceae species, the obligate parasite Striga hermonthica infecting rice and the facultative parasite Phtheirospermum japonicum infecting Arabidopsis. Our images reveal the spatial arrangements of multiple cell types inside haustoria and their interaction with host roots. The 3-D internal structures of haustoria highlight differences between the two parasites, particularly at the xylem connection site with the host. Our study provides structural insights into how organs interact between hosts and parasitic plants.One-sentence summaryThree-dimensional image reconstruction was used to visualize the spatial organization of cell types in the haustoria of parasitic plants with special reference to their interaction with host roots.

Background Root-knot nematodes (RKN, Meloidogyne spp.) are harmful phytophagous pests of Solanum spp. Some RKN species are becoming worldwide problems because of their virulence to RKN-resistant Solanum species. A new Solanum species carrying broad-spectrum resistance to Meloidogyne spp. is required for the effective management of this pest. Here we sought to determine the host suitability of RKN to Solanum palinacanthum, a wild Solanum species, and to evaluate its potential effectiveness in RKN-management. Results We identified an RKN-resistant Solanum species, S. palinacanthum, by screening Solanum accessions. We tested its spectrum of resistance to common Meloidogyne spp. in Japan. in pot tests inoculated with second-stage juveniles, S. palinacanthum showed poor host suitability for Melidogyne incognita, M. arenaria genotypes A2-J and A2-O, M. javanica and M. hapla, indicating broad-spectrum resistance to RKN. The development of M. incognita within S. palinacanthum roots was significantly poorer than that in susceptible S. melongena and S. lycopersicum at 10 and 21 days after inoculation. Microplot tests confirmed that the number of second-stage juveniles in plots where S. palinacanthum grew and root galling of the root system were significantly lower than those of susceptible S. melongena, suggesting that the resistance could be used to manage RKN under field conditions. Conclusion S. palinacanthum showed poor host suitability to all Meloidogyne spp. tested in this study, and it thus has the potential to be used as a genetic resource with broad-spectrum RKN resistance, and it could be effective against multiple RKN species in a field. This article is protected by copyright. All rights reserved.

Most plants show remarkable developmental plasticity in the generation of diverse types of new organs upon external stimuli, allowing them to adapt to their environment. Haustorial formation in parasitic plants is an example of such developmental reprogramming, but its molecular mechanism is largely unknown. In this study, we performed field-omics using transcriptomics and metabolomics to profile the molecular switch occurring in haustorial formation of the root parasitic plant, Thesium chinense, collected from its natural habitat. RNA-sequencing with de novo assembly revealed that the transcripts of very long chain fatty acid (VLCFA) biosynthesis genes, auxin biosynthesis/signaling-related genes and lateral root developmental genes are highly abundant in the haustoria. Gene co-expression network analysis identified a network module linking VLCFAs and the auxin-responsive lateral root development pathway. GC-TOF-MS analysis consistently revealed a unique metabolome profile with many types of fatty acids in the T. chinense root system, including the accumulation of a 25-carbon long chain saturated fatty acid in the haustoria. Our field-omics data provide evidence supporting the hypothesis that the molecular developmental machinery used for lateral root formation in non-parasitic plants has been co-opted into the developmental reprogramming of haustorial formation in the linage of parasitic plants.