Biology subjects

D Aoust, M.-A.

Publications and source records attributed to D Aoust, M.-A..

2 recordsLinked to original sources

bioRxiv2023

Heterologous expression of influenza hemagglutinin leads to early and transient activation of the unfolded protein response in Nicotiana benthamiana

The unfolded protein response (UPR) allows cells to cope with endoplasmic reticulum (ER) stress induced by the accumulation of misfolded proteins in the ER. Due to its sensitivity to Agrobacterium tumefaciens, model plant Nicotiana benthamiana is widely employed for the transient expression of recombinant proteins of biopharmaceutical interest, including therapeutic antibodies and virus surface proteins used for vaccine production. As such, study of the plant UPR is of practical significance, since enforced expression of complex secreted proteins often results in ER stress. After 6 days of expression, we recently reported that influenza hemagglutinin (HA) induces accumulation of UPR proteins. Since the upregulation of corresponding UPR genes was not detected at this time point, accumulation of UPR proteins was hypothesized to either be independent of transcriptional regulation, or associated with early but transient UPR gene upregulation. Using time course sampling, we here show that HA expression does result in early and transient activation of the UPR, as inferred from unconventional splicing of NbbZIP60 transcripts and induction of UPR genes with varied functions. The transient nature of HA-induced UPR suggests that this response was sufficient to cope with ER stress provoked by expression of the secreted protein, as opposed to an antibody that triggered a stronger and more sustained UPR. As defense-related genes were induced after the peak of UPR activation and correlated with high increase in HA protein accumulation, we hypothesize that these immune responses, rather than the UPR, were responsible for the onset of necrotic symptoms on HA-expressing leaves. One-sentence summaryAgrobacterium-mediated expression of influenza hemagglutinin results in early and transient activation of the unfolded protein response, preventing deleterious effects caused by unresolved endoplasmic reticulum stress.

plant biology↗

bioRxiv2023

Molecular responses of agroinfiltrated Nicotiana benthamiana leaves expressing suppressor of silencing P19 and influenza virus-like particles

The production of influenza vaccines in plants is achieved through transient Agrobacterium-mediated expression of viral hemagglutinins (HAs). These proteins are produced and matured through the secretory pathway of plant cells, before being trafficked to the plasma membrane where they induce formation of virus-like particles (VLPs). Production of VLPs unavoidably impacts plant cells, as do viral suppressors of RNA silencing (VSRs) that are often co-expressed to increase protein yields. However, little information is available on host molecular responses to these foreign proteins. The present work provides a comprehensive overview of transcriptomic, metabolic, and signaling changes occurring in Nicotiana benthamiana leaf cells transiently expressing the VSR P19, or co-expressing P19 and an influenza HA. Our data identifies generic responses to Agrobacterium-mediated expression of foreign proteins, including shutdown of chloroplast gene expression, activation of oxidative stress responses, and reinforcement of the plant cell wall through lignification. Our results also indicate that P19 expression promotes salicylic acid (SA) signaling, a process apparently antagonized by co-expression of HA. As the latter induces specific signatures, with effects on lipid metabolism, lipid distribution, and oxylipin signaling, dampening of P19 responses suggests crosstalk between SA and oxylipin pathways. Consistent with the upregulation of oxidative stress-related genes and proteins, we finally show that reduction of oxidative stress damage through exogenous application of ascorbic acid improves plant biomass quality during production of VLPs. One-sentence summaryAgrobacterium-mediated expression of influenza virus-like particles induces a unique molecular signature in Nicotiana benthamiana leaf cells.

plant biology↗