Biology subjects

MacFarlane, S.

Publications and source records attributed to MacFarlane, S..

4 recordsLinked to original sources

bioRxiv2023

Distinguishing integrated sub-viral fragments from infectious Rubus yellow net virus in Scottish commercial red raspberry cultivars

Short read sequencing of two field-grown plants of red raspberry cv Glen Dee identified sequences derived from Rubus yellow net virus (RYNV). Surprisingly, PCR primers designed to target these sequences amplified RYNV-specific DNA fragments from some high health nuclear stock raspberry plants, previously tested as free from RYNV infection. The complete sequence of a Scottish isolate of RYNV (RYNV LG) was determined and a panel of primers covering the entire virus genome was designed to demonstrate that nuclear stock plants of cultivars Glen Dee, Glen Ericht, Glen Fyne and Glen Moy all contain partial fragments of the RYNV genome as integrated elements but do not contain the entire RYNV genome. The complete, circular genome of RYNV could be detected in RYNV LG-infected plants by rolling circle amplification but was not detected in Glen Dee plants. Grafting experiments showed that infectious RYNV could be transferred from RYNV LG plants but not from Glen Dee or Glen Moy plants, further demonstrating that these cultivars contain only partial, integrated RYNV elements. Grafting of RYNV LG to the certification-approved indexing species R. occidentalis (black raspberry) and R. macraei, showed that RYNV LG induced recognisable symptoms in both plants but that R. macraei was more susceptible and produced more recognizable symptoms. Effective testing for RYNV in high health certified raspberry plants can be achieved by combining graft testing with multifragment PCR.

plant biology↗

bioRxiv2022

A hormone-activated mobile RNAi pathway defends plant stem cells from virus infection

Stem cells are essential for the development and organ regeneration of multicellular organisms, so their infection by pathogenic viruses must be prevented. Accordingly, mammalian stem cells are highly resistant to viral infection due to dedicated antiviral pathways including RNA interference (RNAi) (1, 2). In plants, a small group of stem cells harbored within the shoot apical meristem (SAM) generates all postembryonic above-ground tissues, including the germline cells. Many viruses do not proliferate in these cells, yet the molecular bases of this exclusion remain only partially understood (3, 4). Here we show that a plant-encoded RNA-dependent RNA polymerase, after activation by the plant hormone salicylic acid, amplifies antiviral RNAi in infected tissues. This provides stem cells with RNA-based virus sequence information, which prevents virus proliferation. Furthermore, we find RNAi to be necessary for stem cell exclusion of several unrelated RNA viruses, despite their ability to efficiently suppress RNAi in the rest of the plant. This work elucidates a molecular pathway of great biological and economic relevance and lays the foundations for our future understanding of the unique systems underlying stem cell immunity.

plant biology↗

bioRxiv2020

Glia actively sculpt sensory neurons by controlled phagocytosis to tune animal behavior

Glia in the central nervous system engulf neuron fragments during synapse remodeling and recycling of photoreceptor outer-segments. Whether glia passively clear shed neuronal debris, or actively remove neuron fragments is unknown. How pruning of single-neuron endings impacts animal behavior is also unclear. Here we report that adult C. elegans AMsh glia engulf sensory endings of the AFD thermosensory neuron. Engulfment is regulated by temperature, AFDs sensory input, and tracks AFD activity. Phosphatidylserine (PS) flippase TAT-1/ATP8A, functions with glial PS-receptor PSR-1/PSR and PAT-2/-integrin to initiate engulfment. Glial CED-10/Rac1 GTPase, acting through a conserved GEF complex, executes phagocytosis using the actin-remodeler WSP-1/nWASp and the membrane-sealing factor EFF-1 fusogen. CED-10 levels determine engulfment rates, and engulfment-defective mutants exhibit altered AFD-ending shape and thermosensory behavior. Our findings reveal a molecular pathway underpinning glia-dependent phagocytosis in a peripheral sense-organ, and demonstrate that glia actively engulf neuron-fragments, with profound consequences on neuron shape and animal behavior.

neuroscience↗

bioRxiv2019

A plant protein NbP3IP induces autophagy and mediates the autophagic degradation of RSV p3 to inhibit viral infection

In plants, autophagy is involved in responses to viral infection. However, understanding of new host factors mediating autophagic clearance of plant viruses is very limited. We here identified a new host factor NbP3IP participating in autophagy-mediated plant defense against viral infection. NbP3IP interacted with p3, a RNA silencing suppressor encoded by Rice stripe virus (RSV), a negative-strand RNA virus, and mediated its autophagic degradation. NbP3IP could also interact with NbATG8f, which was required for NbP3IP-miediated p3 degradation. Overexpression of NbP3IP induced autophagy and down-regulation of NbP3IP reduced autophagy. Both overexpression of NbP3IP and silencing of GAPC, which also induces autophagy, inhibited RSV infection. In contrast, silencing of ATG7 promoted RSV infection. Thus, through identification of a new potential selective autophagy receptor P3IP, we revealed a new mechanism of autophagy-mediated plant defense against plant viruses and provided the first evidence that plant autophagy can also play an antiviral role against negative-strand RNA viruses.

plant biology↗