Biology subjects

Westwood, J.

Publications and source records attributed to Westwood, J..

5 recordsLinked to original sources

bioRxiv2025

Ethylene-induced host responses enhance resistance against the root-parasitic plant Phelipanche aegyptiaca

AbstractsThe root parasitic plant Phelipanche aegyptiaca and related species pose a grand challenge for agriculture. By directly attaching to host crops to acquire resources, they can severely decrease yields. At the same time, their underground location hides them from sight for much of their life and protects them from typical weed control methods. New strategies for parasitic weed control are needed, with host resistance among the most attractive, but the mechanisms by which hosts respond to parasitic plant attacks are still unclear. In plants, the phytohormone ethylene is a crucial modulator responding to various stresses such as flooding and pathogen attack, and our data suggest that ethylene signaling may be important in host response to P. aegyptiaca. Here, we demonstrated that ethylene plays a role against P. aegyptiaca using two host plants, Arabidopsis and tomato. Arabidopsis plants with the ethylene reporter construct (EBS::GUS) were analyzed and revealed that stress from excess water and P. aegyptiaca parasitism both induced ethylene responses in the host Arabidopsis roots. We also observed that applying an ethylene precursor (ACC) to host roots inhibits the attachment of P. aegyptiaca. Lines of Arabidopsis and tomato with mutations in Ethylene-Resistant 1 (ETR1) and Constitutive Triple-Response 1 (CTR1) have altered tolerance to P. aegyptiaca, suggesting that the ethylene signaling pathway is associated with enhanced resistance to parasitism. These results point to ethylene-mediated responses as a starting point to gain insight into host response to parasitism, with potential to increase host resistance to parasitic plants.

plant biology↗

bioRxiv2024

Agrobacterium-mediated Cuscuta campestris transformation as a tool for understanding plant-plant interactions

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 to C. campestris research is that a method to generate stable transgenic plants has not yet been developed. Here, we describe the development of a Cuscuta transformation protocol using various reporter genes (GFP, GUS, or RUBY) and morphogenic genes (CcWUS2 and CcGRF/GIF), ultimately leading to a robust protocol for Agrobacterium-mediated C. campestris transformation. The stably transformed and regenerated RUBY C. campestris plants 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. Transformed C. campestris also produced flowers and transgenic seeds exhibiting betalain pigment, providing proof of germline transmission of the RUBY transgene. Furthermore, the RUBY reporter is not only a useful selectable marker for the Agrobacterium-mediated transformation, but also provides insight into the movement of molecules from C. campestris to the host during parasitism. Thus, the protocol for transformation of C. campestris reported here overcomes a major obstacle to Cuscuta research and opens new possibilities for studying parasitic plants and their interactions with hosts.

plant biology↗

bioRxiv2022

An Orobanche cernua x Orobanche cumana segregating population provides insight into the regulation of germination specificity in a parasitic plant

Germination of seeds of Orobanche species requires specific chemicals exuded by host roots. A family of "divergent" KARRIKIN INSENSITIVE2 (KAI2d) genes encode proteins that recognize strigolactone (SL) class germination simulants. We explored specificity of germination stimulant detection by analyzing interspecific segregants of a cross between Orobanche cernua and O. cumana, closely related species that differ in stimulant response. O. cernua parasitizes tomato and germinates in response to the SL orobanchol, while O. cumana parasitizes sunflower and responds to dehydrocostus lactone (DCL). KAI2d genes were catalogued in parents and in segregants that showed stimulant specificity. KAI2d genes were also functionally assayed in the Arabidopsis kai2 mutant background. We identified five full-length KAI2d genes in O. cernua and eight in O. cumana. The O. cernua KAI2d2, as well as its ortholog in O. cumana, are associated with SL perception. A cluster of O. cumana KAI2d genes was genetically linked to DCL perception, although no specific receptor gene was identified by heterologous complementation. These findings support the KAI2d-mediated perception of SLs, but fall short of explaining how O. cumana perceives DCL. The ability of some O. cumana KAI2d genes to detect SLs points to the involvement of additional factors in regulating stimulant specificity.

plant biology↗

bioRxiv2021

An artificial host system enables the obligate parasitic plant Cuscuta campestris to grow and complete its life cycle in vitro

Cuscuta campestris is an obligate parasitic plant that requires a host to complete its lifecycle. Parasite-host connections occur via an haustorium, a unique organ that acts as a bridge for the uptake of water, nutrients and macromolecules. Research on Cuscuta is often complicated by host influences, but comparable systems for growing the parasite in the absence of a host do not exist. We developed an axenic method to grow C. campestris on an Artificial Host System (AHS). We evaluated the effects of nutrients and phytohormones on parasite haustoria development and growth. Haustorium morphology and gene expression were characterized. The AHS consists of an inert, fibrous stick that mimics a host stem, wicking water and nutrients to the parasite. It enables C. campestris to exhibit a parasitic habit and develop through all stages of its lifecycle, including production of new shoots and viable seeds. Phytohormones NAA and BA affect haustoria morphology, and increase parasite fresh weight and biomass. Gene expression in AHS haustoria reflect process similar to those in haustoria on actual host plants. The AHS is a methodological improvement for studying Cuscuta biology by avoiding specific host effects on parasite and giving researchers full control of the parasite environment.

plant biology↗

bioRxiv2018

A role for phylloquinone biosynthesis in the plasma membrane as revealed in a non-photosynthetic parasitic plant

Phylloquinone is a lipophilic naphthoquinone found predominantly in chloroplasts and best known for its function in photosystem I electron transport and disulfide bridge formation of photosystem II subunits. Phylloquinone has also been detected in plasma membrane preparations of heterotrophic tissues with potential transmembrane redox function, but the molecular basis for this noncanonical pathway is unknown. Here we provide evidence of plasma membrane phylloquinone biosynthesis in a nonphotosynthetic holoparasite Phelipanche aegyptiaca. A nonphotosynthetic and nonplastidial role for phylloquinone is supported by transcription of phylloquinone biosynthetic genes during seed germination and haustorium development, by plasma membrane-localization of alternative terminal enzymes, and by detection of phylloquinone in germinated seeds. Comparative gene network analysis with photosynthetically competent parasites revealed a bias of Phelipanche phylloquinone genes toward coexpression with oxidoreductases involved in plasma membrane electron transport. Genes encoding the plasma membrane phylloquinone pathway are also present in several photoautotrophic taxa of Asterids, suggesting an ancient origin of multifunctionality. Our findings suggest that nonphotosynthetic holoparasites exploit alternative targeting of phylloquinone for transmembrane redox signaling associated with parasitism.

plant biology↗