Assessing Seed Germination Response of Parasitic Plant Striga hermonthica with Small-Molecule Probes.

Seed germination of a parasitic plant Striga hermonthica is elicited by strigolactones which are exuded from roots of host plants. Here, we describe a high-throughput germination assay and a method for visualizing in vivo strigolactone receptor functions with a fluorogenic probe.

Radicle growth regulation of root parasitic plants by auxin-related compounds.

Root parasitic plants in the Orobancheceae, such as Striga and Orobanche, cause significant damage to crop production. The germination step of these root parasitic plants is induced by host-root-derived strigolactones (SLs). After germination, the radicles elongate toward the host and invade the host root. We have previously discovered that a simple amino acid, tryptophan (Trp), as well as its metabolite, the plant hormone indole-3-acetic acid (IAA), can inhibit radicle elongation of Orobanche minor. These results suggest that auxin plays a crucial role in the radicle elongation step in root parasitic plants. In this report, we used various auxin chemical probes to dissect the auxin function in the radicle growth of O. minor and Striga hermonthica. We found that synthetic auxins inhibited radicle elongation. In addition, auxin receptor antagonist, auxinole, rescued the inhibition of radicle growth by exogenous IAA. Moreover, a polar transport inhibitor of auxin, N-1-naphthylphthalamic acid (NPA), affected radicle bending. We also proved that exogenously applied Trp is converted into IAA in O. minor seeds, and auxinole partly rescued this radicle elongation. Our data demonstrate a pivotal role of auxin in radicle growth. Thus, manipulation of auxin function in root parasitic plants should offer a useful approach to combat these parasites.

Tracking the messengers: Emerging advances in mRNA-based plant communication.

Messenger RNAs (mRNAs) are the templates for protein translation but can also act as non-cell-autonomous signaling molecules. Plants input endogenous and exogenous cues to mobile mRNAs and output them to local or systemic target cells and organs to support specific plant responses. Mobile mRNAs form ribonucleoprotein (RNP) complexes with proteins during transport. Components of these RNP complexes could interact with plasmodesmata (PDs), a major mediator of mRNA transport, to ensure mRNA mobility and transport selectivity. Based on advances in the last two to three years, this review summarizes mRNA transport mechanisms in local and systemic signaling from the perspective of RNP complex formation and PD transport. We also discuss the physiological roles of endogenous mRNA transport and the recently revealed roles of non-cell-autonomous mRNAs in inter-organism communication.

Parasitic dodder expresses an arsenal of secreted cellulases with multi-substrate specificity during host invasion.

Cuscuta campestris is a common and problematic parasitic plant which relies on haustoria to connect to and siphon nutrients from host plants. Glycoside hydrolase family 9 (GH9) cellulases (EC 3.2.1.4) play critical roles in plant cell wall biosynthesis and disassembly, but their roles during Cuscuta host invasion remains underexplored. In this study, we identified 22 full-length GH9 cellulase genes in C. campestris genome, which encoded fifteen secreted and seven membrane-anchored cellulases that showed distinct phylogenetic relationships. Expression profiles suggested that some of the genes are involved in biosynthesis and remodeling of the parasite's cell wall during haustoriogenesis, while other genes encoding secreted B- and C-type cellulases are tentatively associated with degrading host cell walls during invasion. Transcriptomic data in a host-free system and in the presence of susceptible or partially resistant tomato hosts, showed for especially GH9B7, GH9B11 and GH9B12 a shift in expression profiles in the presence of hosts, being more highly expressed during host attachment, indicating that Cuscuta can tune cellulase expression in response to a host. Functional analyses of recombinant B- and C-type cellulases showed endoglucanase activities over wide pH and temperature conditions, and activities towards multiple cellulose and hemicellulose substrates. These findings improve our understanding of host cell wall disassembly by Cuscuta, and cellulase activity towards broad substrate range potentially explain its wide host range. This is the first study to provide a broad biochemical insight into Cuscuta GH9 cellulases, which based on our study may have potential applications in industrial bioprocessing.

An account of the genus Cistanche (Orobanchaceae) in Iraq and taxonomic considerations in the Middle East.

Species limits in the genus Cistanche are poorly understood, despite the plants' long history of use in traditional herbal medicine and food across their range. Here we present a taxonomic account for the genus Cistanche in Iraq, where several taxa have been reported, most of them doubtfully. Using herbarium specimens, images of living material, and taxonomic literature, we found evidence of only one species occurring with certainty in Iraq: Cistanchetubulosa. We found no evidence for the occurrence of other Cistanche species in Iraq, including a putative new entity reported for the region. Our work highlights inconsistencies in the literature, and underscores the importance of examining multiple stable characters for delimiting species in the genus Cistanche.

Large-scale interplant exchange of macromolecules between soybean and dodder under nutrient stresses.

Parasitic plants and their hosts communicate through haustorial connections. Nutrient deficiency is a common stress for plants, yet little is known about whether and how host plants and parasites communicate during adaptation to such nutrient stresses. In this study, we used transcriptomics and proteomics to analyze how soybean (Glycine max) and its parasitizing dodder (Cuscuta australis) respond to nitrate and phosphate deficiency (-N and -P). After -N and -P treatment, the soybean and dodder plants exhibited substantial changes of transcriptome and proteome, although soybean plants showed very few transcriptional responses to -P and dodder did not show any transcriptional changes to either -N or -P. Importantly, large-scale interplant transport of mRNAs and proteins was detected. Although the mobile mRNAs only comprised at most 0.2% of the transcriptomes, the foreign mobile proteins could reach 6.8% of the total proteins, suggesting that proteins may be the major forms of interplant communications. Furthermore, the interplant mobility of macromolecules was specifically affected by the nutrient regimes and the transport of these macromolecules was very likely independently regulated. This study provides new insight into the communication between host plants and parasites under stress conditions.

Conocimiento local del género Arceuthobium en un área natural protegida del centro de México / Local knowledge of Arceuthobium genus in a natural protected area of the centre of Mexico

El género Arceuthobium (muérdago enano) es una de las principales plagas en los bosques templados de México, con antecedentes de uso medicinal y forrajero. El objetivo de este trabajo fue documentar el conocimiento local sobre los usos del muérdago enano en el Área Natural Protegida Nevado de Toluca, México, bajo las perspectivas emic y etic, a través de la etnobotánica. Mediante entrevistas se identificó que ambas especies (A. vaginatum y A. globosum) son conocidas como muérdago y forman parte de la flora del bosque; sin embargo, los entrevistados desconocen los efectos negativos dentro de los ecosistemas forestales de esta plaga. Destacan los usos lúdicos, como juguete y tinta, y los medicinales para el tratamiento de afecciones respiratorias y del sistema nervioso, siendo éste el primer registro para dicho género localmente. Se requieren estudios que validen el conocimiento local para su inclusión en programas locales de manejo de plagas forestales.

Arceuthobium (dwarf mistletoe) genus is one of the main pests in temperate forests of Mexico, with records of medicinal and forage uses. The objective of this work was to document local knowledge regarding uses of dwarf mistletoe in the Natural Protected Area Nevado de Toluca, Mexico, under emic and etic perspectives, through ethnobotany. Throughout interviews it was identified that both species (A. vaginatum and A. globosum) are known as mistletoe and they are part of flora in forest, however, interviewees are not aware of negative effects within forest ecosystems of this pest. It stands out ludic uses as a toy and ink, and medicinal ones for treatment of respiratory diseases and nervous system, being this the first record for such genus locally. Studies are required to validate the local knowledge for its inclusion in local programmes for management of forest pests.

SEED GERMINATION AND PLANT DEVELOPMENT IN Escobedia grandiflora (OROBANCHACEAE): EVIDENCE OF OBLIGATE HEMIPARASITISM? / Germinación de semillas y desarrollo de plantas en Escobedia grandiflora (Orobanchaceae): ¿Evidencia de hemiparasitismo obligado?

Root parasitic plants can be facultative or obligate. Facultative parasites are able to complete their life cycle and their seeds can germinate without a host. Escobedia grandiflora is a poorly studied species in spite of its ancestral importance as dye of foods and medicinal use. The present study evaluates the states of seed, seedlings and mature plants, under presence and absence of possible hosts, for inferring the type of parasitism exhibited by E. grandiflora. Seeds were evaluated using two conditions each of light (12 and 0 hours) and temperature (20 °C and 25 °C); percentage germination, and germination speed were determined. The seeds did not require a host to germinate, as is typical of facultative parasitic plants. Percentage of germination varied between 66 % and 85.3 % and was not affected by light or temperature although germination speed was greater at 25 °C. Larger seeds had a higher percentage of germination and produced larger seedlings. The seedlings planted without a host did not survive, while those planted with Paspalum notatum had a 45 % survival rate, demonstrating that this is a critical stage of development, even with a host. Escobedia grandiflora plants sowed with grasses began the reproductive stage at the 28th week, and those planted with Pennisetum purpureum showed better performance, expressed in more haustoria, higher dry matter of total plant, rhizome and aerial stems. Plants sowed alone lived for more than six months, but they did not produce flowers or fruits. According to the behavior of seedlings and plants, E. grandiflora is an obligate parasite.

Las plantas parásitas de raíces pueden ser facultativas u obligadas, las primeras pueden completar su ciclo de vida y sus semillas pueden germinar sin un hospedero. Escobedia grandiflora es una especie poco estudiada, a pesar de su importancia ancestral como colorante de alimentos y uso medicinal. Este estudio evaluó los estados de semilla, plántula y planta adulta, en presencia y ausencia de posibles hospederos para inferir sobre su tipo de parasitismo. En las semillas se evaluaron dos condiciones de luz (12 y 0 horas) y temperatura (20 °C y 25 °C), el porcentaje y velocidad de germinación. Las semillas no requirieron la presencia del hospedero para germinar. El porcentaje de germinación osciló entre 66 y 85,3 % y no fue afectado por la luz o la temperatura, aunque la velocidad de germinación fue mayor a 25 °C. Las semillas con mayor tamaño presentaron mayor porcentaje de germinación y produjeron plántulas más grandes. Las plántulas sembradas sin hospedero no sobrevivieron, mientras que las sembradas con Paspalum notatum, tuvieron una sobrevivencia del 45 %, evidenciando que este estado es crítico, aún con hospedero. Las plantas de Escobedia grandiflora sembradas con pastos, iniciaron la etapa reproductiva en la semana 28, y aquellas sembradas con Pennisetum purpureum presentaron más haustorios, y mayor materia seca en la planta total, rizoma y tallos aéreos. Las plantas sembradas solas vivieron más de seis meses, pero ellas no desarrollaron flores y ni frutos. Según el comportamiento de las plántulas y las plantas, E. grandiflora es parásita obligada.