Content and composition of maize endosperm lipids and their partition in the floury and vitreous regions were determined for a set of inbred lines. Neutral lipids, i.e., triglycerides and free fatty acids, accounted for more than 80% of endosperm lipids and are almost 2 times higher in the floury than in the vitreous regions. The composition of endosperm lipids, including their fatty acid unsaturation levels, as well as their distribution may be related to metabolic specificities of the floury and vitreous regions in carbon and nitrogen storage and to the management of stress responses during endosperm cell development. Remarkably, the highest contents of starch lipids were observed systematically within the vitreous endosperm. These high amounts of starch lipids were mainly due to lysophosphatidylcholine and were tightly linked to the highest amylose content. Consequently, the formation of amylose-lysophosphatidylcholine complexes has to be considered as an outstanding mechanism affecting endosperm vitreousness.

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Rose rosette virus (RRV) is a negative-sense RNA virus with a seven-segmented genome that is enclosed by a double membrane. We constructed an unconventional minireplicon system encoding the antigenomic (ag)RNA1 (encoding the viral RNA-dependent RNA polymerase [RdRp]), agRNA3 (encoding the nucleocapsid protein [N]), and a modified agRNA5 containing the coding sequence for the iLOV protein in place of the P5 open reading frame (R5-iLOV). iLOV expression from the R5-iLOV template was amplified by activities of the RdRp and N proteins in Nicotiana benthamiana leaves. A mutation was introduced into the RdRp catalytic domain and iLOV expression was eliminated, indicating RNA1-encoded polymerase activity drives iLOV expression from the R5-iLOV template. Fluorescence from the replicon was highest at 3 days postinoculation (dpi) and declined at 7 and 13 dpi. Addition of the tomato bushy stunt virus (TBSV) P19 silencing-suppressor protein prolonged expression until 7 dpi. A full-length infectious clone system was constructed of seven binary plasmids encoding each of the seven genome segments. Agro-delivery of constructs encoding RRV RNAs 1 through 4 or RNAs 1 through 7 to N. benthamiana plants produced systemic infection. Finally, agro-delivery of the full-length RRV infectious clone including all segments produced systemic infection within 60 dpi. This advance opens new opportunities for studying RRV infection biology. [Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Endoplasmic reticulum (ER) stress due to biotic or abiotic stress activates the unfolded protein response (UPR) to restore ER homeostasis. The UPR relies on multiple ER-to-nucleus signaling factors which mainly induce the expression of cytoprotective ER-chaperones. The inositol requiring enzyme (IRE1) along with its splicing target, bZIP60, restrict potyvirus, and potexvirus accumulation. Until now, the involvement of the alternative UPR pathways and the role of UPR to limit virus accumulation have remained elusive. Here, we used the Plantago asiatica mosaic virus (PlAMV) and the Turnip mosaic virus (TuMV) to demonstrate that the potexvirus triple gene block 3 (TGB3) protein and the potyvirus 6K2 protein activate the bZIP17, bZIP28, bZIP60, BAG7, NAC089 and NAC103 signaling in Arabidopsis thaliana. Using the corresponding knockout mutant lines, we demonstrated that these factors differentially restrict local and systemic virus accumulation. We show that bZIP17, bZIP60, BAG7, and NAC089 are factors in PlAMV infection, whereas bZIP28 and bZIP60 are factors in TuMV infection. TGB3 and 6K2 transient expression in leave reveal that these alternative pathways induce BiPs expression. Finally, using dithiothreitol (DTT) and tauroursodeoxycholic acid (TUDCA) treatment, we demonstrated that the protein folding capacity significantly influences PlAMV accumulation. Together, these results indicate that multiple ER-to-nucleus signaling pathways are activated during virus infection and restrict virus accumulation through increasing protein folding capacity.

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