Biology subjects

Pare, M.-E.

Publications and source records attributed to Pare, M.-E..

3 recordsLinked to original sources

bioRxiv2024

Molecular changes in agroinfiltrated leaves of Nicotiana benthamiana expressing suppressor of silencing P19 and coronavirus-like particles

The production of coronavirus disease 2019 vaccines can be achieved by transient expression of the Spike (S) protein of Severe Acute Respiratory Syndrome Coronavirus 2 in agroinfiltrated leaves of Nicotiana benthamiana. Relying on bacterial vector Agrobacterium tumefaciens, this process is favored by the co-expression of viral silencing suppressor P19. Upon expression, the S protein enters the cell secretory pathway, before being trafficked to the plasma membrane where formation of coronavirus-like particles (CoVLPs) occurs. We previously characterized effects of influenza virus hemagglutinin forming VLPs through similar processes. However, leaf samples were only collected after six days of expression and it remains unknown whether influenza VLPs and CoVLPs induce similar responses. Here, time course sampling was used to profile responses of N. benthamiana leaf cells expressing P19 only, or P19 along with the S protein. The latter triggered early, but transient activation of the unfolded protein response and waves of transcription factor genes involved in immunity. Accordingly, defense genes were induced with different expression kinetics, including those promoting lignification, terpene biosynthesis, and oxidative stress. Crosstalk between stress hormone pathways also occurred, notably leading to the repression of jasmonic acid biosynthesis genes after agroinfiltration, and dampening of salicylic acid-inducible responses upon S protein accumulation. Overall, influenza VLP- and CoVLP-induced responses broadly overlapped, suggesting nanoparticle production to have the most effects on plant immunity, regardless of the virus surface proteins expressed. Taking advantage of RNAseq inferences, we finally show the co-expression of Kunitz trypsin inhibitors to reduce CoVLP-induced defense and leaf symptoms, with no adverse effect on plant productivity.

plant biology↗

bioRxiv2024

Expression of a constitutively active nitrate reductase increases SARS-CoV-2 Spike protein production in Nicotiana benthamiana leaves that otherwise show traits of senescence

The production of coronavirus disease 2019 vaccines can be achieved by transient expression of the Spike (S) protein of Severe Acute Respiratory Syndrome Coronavirus 2 in agroinfiltrated leaves of Nicotiana benthamiana, a process promoted by the co-expression of viral silencing suppressor P19. Upon expression, the S protein enters the cell secretory pathway, before being trafficked to the plasma membrane where formation of coronavirus-like particles (CoVLPs) occurs. We recently used RNAseq and time course sampling to characterize molecular responses of N. benthamiana leaf cells expressing P19 only, or P19 in combination with recombinant S protein. This revealed expression of the viral proteins to deeply affect the physiological status of plant cells, including through the activation of immune responses. Here, transcriptomics shows that the production of CoVLPs also induces leaf senescence, as revealed by the upregulation of senescence-associated genes, activation of senescence-related proteases, and downregulation of genes involved in basic metabolic functions like photosynthesis or nitrogen uptake and assimilation. CoVLP production also upregulated asparagine synthetase genes and led to consequent accumulation of asparagine, a nitrogen-rich amino acid is known to facilitate the reallocation of nitrogen resources from senescent to young growing organs. Hypothesizing these combined host responses to restrain foreign protein accumulation, an attempt was made to support nitrogen reduction in CoVLP-producing leaves by co-expressing a constitutively active, light-insensitive form of the nitrate reductase. We show this strategy to increase S protein accumulation in leaf tissues, thereby suggesting that boosting nitrogen metabolism of agroinfiltrated leaves improves recombinant protein yields in N. benthamiana.

plant biology↗

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↗