Tobacco alpha-expansin EXPA4 plays a role in Nicotiana benthamiana defence against Tobacco mosaic virus

Abstract

Tobacco EXPA4 plays a role in Nicotiana benthamiana defence against virus attack and affects antioxidative metabolism and phytohormone-mediated immunity responses in tobacco. Expansins are cell wall-loosening proteins known for their endogenous functions in cell wall extensibility during plant growth. The effects of expansins on plant growth, developmental processes and environment stress responses have been well studied. However, the exploration of expansins in plant virus resistance is rarely reported. In the present study, virus-induced gene silencing (VIGS) and Agrobacterium-mediated transient overexpression were conducted to investigate the role of Nicotiana tabacum alpha-expansin 4 (EXPA4) in modulating Tobacco mosaic virus (TMV-GFP) resistance in Nicotiana benthamiana. The results indicated that silencing of EXPA4 reduced the sensitivity of N. benthamiana to TMV-GFP, and EXPA4 overexpression accelerated virus reproduction on tobacco. In addition, our data suggested that the changes of virus accumulation in response to EXPA4 expression levels could further affect the antioxidative metabolism and phytohormone-related pathways in tobacco induced by virus inoculation. EXPA4-silenced plants with TMV-GFP have enhanced antioxidant enzymes activities, which were down-regulated in virus-inoculated 35S:EXPA4 plants. Salicylic acid accumulation and SA-mediated defence genes induced by TMV-GFP were up-regulated in EXPA4-silenced plants, but depressed in 35S:EXPA4 plants. Furthermore, a VIGS approach was used in combination with exogenous phytohormone treatments, suggesting that EXPA4 has different responses to different phytohormones. Taken together, these results suggested that EXPA4 plays a role in tobacco defence against viral pathogens.

The Expression of Potato Expansin A3 (StEXPA3) and Extensin4 (StEXT4) Genes with Distribution of StEXPAs and HRGPs-Extensin Changes as an Effect of Cell Wall Rebuilding in Two Types of PVYNTN–Solanum tuberosum Interactions

“…It was also emphasized that sRNAs corresponding to EXP10, PME3, and XTH6 were induced in response to TuMV at 10 days post-inoculation. Additionally, our presented results were similar to investigations conducted by Chen et al [17], who stated that low levels of EXPA4 in Nicotiana benthamiana plants significantly downregulated the sensitivity of tobacco to infection by the constructed Tobacco mosaic virus-green fluorescence protein (TMV-GFP). Moreover, Chen et al [17] postulated that EXPA4 overexpression accelerated virus reproduction and disease development in tobacco.…”

“…Similarly, as presented by Abuqamar et al [16], the downregulation or knockdown of AtEXLA2 enhanced resistance to the necrotrophic fungus Alternaria brassicicola. Furthermore, the EXPA4 gene negatively regulated the defense response against TMV in N. benthamiana [17] but enhanced abiotic stress tolerance [18]. However, aside from a role in plant abiotic stress, the influence of the EXPA3 gene on plant-pathogen interactions was well-documented, but only for the Arabidopsis-cyst nematode pathosystem, by Wieczorek et al [19].…”

“…Moreover, it is still not clear which expansins are involved in this particular type of biotic stress. However, some preliminary data regarding the involvement of EXPA1 or EXPA4 genes in the Solanaceous plant-virus pathosystem were reported [15,17]. We decided to focus on the role of the StEXPA3 gene and determine the relative expression and distribution of selected kinds of expansin proteins during two types of interactions between potato virus Y (PVY NTN ) and potato plants.…”

Massive up‐regulation of LBD transcription factors and EXPANSINs highlights the regulatory programs of rhizomania disease

“…Among the factors studied during rhizomania development, EXP s are primarily known for their role in plant CW remodelling by breaking the hydrogen bonds between cellohexaose and pectin; they thus participate in various aspects of plant development involving cell division and expansion (Cosgrove, ), and as potential pro‐viral factors (Chen et al., ; Park et al., ). The data accumulated from studies in various plant pathosystems, including nematodes, fungi and viruses, suggest that the down‐regulation of EXP s may represent a defence response (Marowa et al., ).…”

“…Furthermore, it has been shown that NbEXPA1 is a plasmodesmata‐specific protein recruited by TuMV to the virus replication complex through its interaction with the viral RNA‐dependent RNA polymerase, the NIb protein, and transient expression of NbEXPA1 promotes TuMV replication and cell‐to‐cell movement (Park et al., ). Similarly, the knockdown of NbEXPA4 expression reduces Tobacco mosaic virus (TMV) accumulation in systemically infected plants, whereas the overexpression of NbEXPA4 accelerates virus replication (Chen et al., ). The pro‐viral role of EXPs is further supported (this study) by the up‐regulation of 13 EXP genes by natural soil‐mediated infection with BNYVV, among which four root‐specific EXP s are up‐regulated in susceptible, but not resistant, varieties, linking the activation of these EXP s to rhizomania development.…”