MAP30 and luffin-α: Novel ribosome-inactivating proteins induce plant systemic resistance against plant viruses.

Ribosome-inactivating proteins (RIPs) are toxic N-glycosylase that act on eukaryotic and prokaryotic rRNAs, resulting in arrest protein synthesis. RIPs are widely found in higher plant species and display strong antiviral activity. Previous studies have shown that PAP and α-MMC have antiviral activity against TMV. However, the localization of RIPs in plant cells and the mechanism by which RIPs activate plant defense against several plant viruses remain unclear. In this study, we obtained four RIPs (the C-terminal deletion mutant of pokeweed antiviral proteins (PAP-c), alpha-momorcharin (α-MMC), momordica anti-HIV protein of 30 kDa (MAP30) and luffin-α). The subcellular localization results indicated that these four RIPs were located on the plant cell membrane. Heterologous expression of RIPs (PAP-c, α-MMC, MAP30, luffin-α) enhanced tobacco mosaic virus (TMV) resistance in N. benthamiana. Compared with the control treatment, these RIPs significantly reduced the TMV content (149-357 fold) and altered the movement of TMV in the leaves of N. benthamiana. At the same time, heterologous expression of RIPs (MAP30 and luffin-α) could relieve TMV-induced oxidative damage, significantly inducing the expression of plant defense genes including PR1 and PR2. Furthermore, application of these RIPs could inhibit the infection of turnip mosaic virus (TuMV) and potato virus x (PVX). Therefore, this study demonstrated that MAP30 and luffin-α could be considered as new, effective RIPs for controlling plant viruses by activating plant systemic defense.

Fabrication of an alginate-based ZhiNengCong gel showed an enhanced antiviral and plant growth promoting functions.

Tobacco mosaic disease is a worldwide viral disease that can cause huge economic losses. Plant immune inducers have become the main force in the prevention and treatment of viral disease own to their high efficiency and rapid effect. However, since tobacco mosaic disease can occur at any point in the plant growth cycle, a single application period cannot guarantee the completely management. In this study, an extract from Paecilomyces variotii named ZhiNengCong (ZNC), which can fight against tobacco mosaic disease with 65% control effect, and improve the promotion of tobacco stem girth, was selected from five commercial antiviral medicines, and a sustained release sodium alginate (Alg)-based ZNC (ZNC@Alg) was prepared by physical absorption. ZNC@Alg, who contains only 5 mg/mL ZNC, can release ZNC for 7 consecutive days, and displayed an enhanced effect in inducing the PAL-mediated salicylic acid signaling pathway activation to participate in the inhibition of green fluorescent protein (GFP)-tagged tobacco mosaic virus (TMV-GFP) infection, even after 7 days of the application. Notably, field experiments showed that the control effect of ZNC@Alg was up to 88%, which was significantly better than that of ZNC with the same concentration (10 µg per plant). In addition, ZNC@Alg exhibited a stronger growth-promoting effect than ZNC, which significantly increased the wet weight of tobacco. Taken together, we screened out a plant immune inducer ZNC that can effectively inhibit tobacco virus disease, and created ZNC@Alg with higher control effect and growth promotion effect, laying a foundation for effective field management of tobacco mosaic disease.