Maize resistance to insect herbivory is enhanced by silencing expression of genes for jasmonate‐isoleucine degradation using sugarcane mosaic virus

Abstract

Previously, sugarcane mosaic virus (SCMV) was developed as a vector for transient expression of heterologous genes in Zea mays (maize). Here, we show that SCMV can also be applied for virus-induced gene silencing (VIGS) of endogenous maize genes. Comparison of sense and antisense VIGS constructs targeting maize phytoene desaturase (PDS) showed that antisense constructs resulted in a greater reduction in gene expression. In a time course of gene expression after infection with VIGS constructs targeting PDS, lesion mimic 22 (Les22), and Iodent japonica 1 (Ij1), efficient expression silencing was observed 2, 3, and 4 weeks after infection with SCMV. However, at Week 5, expression of Les22 and Ij1 was no longer significantly reduced compared with control plants. The defense signaling molecule jasmonate-isoleucine (JA-Ile) can be inactivated by 12C-hydroxylation and hydrolysis, and knockout of these genes leads to herbivore resistance. JA-Ile hydroxylases and hydrolases have been investigated in Arabidopsis, rice, and Nicotiana attenuata. To determine whether the maize homologs of these genes function in plant defense, we silenced expression of ZmCYP94B1 (predicted JA-Ile hydroxylase) and ZmJIH1 (predicted JA-Ile hydrolase) by VIGS with SCMV, which resulted in elevated expression of two defense-related genes, Maize Proteinase Inhibitor (MPI) and Ribosome Inactivating Protein 2 (RIP2). Although ZmCYP94B1 and ZmJIH1 gene expression silencing increased resistance to Spodoptera frugiperda (fall armyworm), Schistocerca americana (American birdwing grasshopper), and Rhopalosiphum maidis (corn leaf aphid), there was no additive effect from silencing the expression of both genes. Further work will be required to determine the more precise functions of these enzymes in regulating maize defenses.

Influence of plant defense signaling and innate insect metabolic differences to the overall performance of fall armyworm (Spodoptera frugiperda) corn and rice strains on maize as a host

“…JA signaling can also be regulated through metabolism of JA-Ile via 12-hydroxylation and subsequent hydrolysis and silencing of genes pertinent to this reaction have been already shown to have consequences for resistance to FAW (Chung et al 2022). In our study, the amounts of 12-hydroxy JA and 12-hydroxy JA-Ile were higher after 24 hours of rice versus corn strain herbivory.…”

Foxtail mosaic virus: A tool for gene function analysis in maize and other monocots

“…Protein expression in maize has been demonstrated via insertion of cloning sites that allow these viruses to express proteins from sequences that are cloned in frame with the viral polyprotein (Mei et al, 2019 ; Tatineni et al, 2010 ; Xie et al, 2021 ). Interestingly, gene fragments for VIGS applications can also be inserted into these positions as long as the open reading frame (ORF) is preserved (Chung et al, 2022 ; Xie et al, 2021 ). Moreover, it was shown that MDMV can be used to simultaneously express a protein and silence multiple target genes in maize plants (Xie et al, 2021 ).…”

Inoculation of Maize with Sugarcane Mosaic Virus Constructs and Application for RNA Interference in Fall Armyworms

“…Several virus vectors have been used for VIGS in monocot plant species, including Chinese wheat mosaic virus ( Yang et al, 2018 ), tobacco rattle virus (TRV) ( Zhong et al, 2014 ), barley stripe mosaic virus ( Buhrow et al, 2016 ), brome mosaic virus ( Wang et al, 2021 ), bamboo mosaic virus, cymbidium mosaic virus ( Hsieh et al, 2013 ), rice tungro bacilliform virus ( Purkayastha et al, 2010 ), cucumber mosaic virus ( Tzean et al, 2019 ), foxtail mosaic virus ( Liu et al, 2016 ), maize rayado fino virus ( Mlotshwa et al, 2020 ), and sugarcane mosaic virus (SCMV) ( Mei et al, 2019 ; Chung et al, 2022 ). Several of these viruses, including SCMV, have been used for VIGS in maize ( Mei et al, 2016 ; Wang et al, 2016 ; J. Zhang et al, 2017 ; Ding et al, 2018 ; Jarugula et al, 2018 ; Mlotshwa et al, 2020 ; Chung et al, 2022 )…”

“…SCMV is a positive strand RNA virus of the Potyviridae family that infects many monocots including sugarcane, maize, wheat, and sorghum ( Xiao et al, 1993 ). Previously, SCMV has been used as a vector for transient overexpression of non-maize genes ( Mei et al, 2019 ), overexpression of maize endogenous genes ( Chung et al, 2021 ), VIGS of maize endogenous genes ( Chung et al, 2022 ), and plant-mediated VIGS of gene expression in corn leaf aphids ( Rhopalosiphum maidis ) feeding on maize ( Chung and Jander, 2022 ). The plasmid vector pSCMV-CS3 ( Mei et al, 2019 ; Chung et al, 2022 ) allows for both efficient gene overexpression and gene expression silencing by RNA interference.…”

“…Previously, SCMV has been used as a vector for transient overexpression of non-maize genes ( Mei et al, 2019 ), overexpression of maize endogenous genes ( Chung et al, 2021 ), VIGS of maize endogenous genes ( Chung et al, 2022 ), and plant-mediated VIGS of gene expression in corn leaf aphids ( Rhopalosiphum maidis ) feeding on maize ( Chung and Jander, 2022 ). The plasmid vector pSCMV-CS3 ( Mei et al, 2019 ; Chung et al, 2022 ) allows for both efficient gene overexpression and gene expression silencing by RNA interference. The entire SCMV virus is encoded between a cauliflower mosaic virus 35S promoter and a nopaline synthase terminator in the Escherichia coli plasmid pSCMV-CS3.…”