Rapid screening of pest resistance genes in maize using a sugarcane mosaic virus vector

Abstract

Spodoptera frugiperda (fall armyworm) is a notorious pest that threatens maize production world-wide. Current control measures involve the use of chemical insecticides and transgenic maize expressing Bacillus thuringiensis (Bt) toxins. Although several additional transgenes have confirmed insecticidal activity in other plants, limited research has been conducted in maize, at least partially due to the technical difficulty of maize transformation. Here, we describe implementation of a sugarcane mosaic virus (SCMV) vector for rapidly testing the efficacy of transgenes for the control of S. frugiperda in maize. Four categories of proteins were tested using the SCMV vector: (i) maize defense signaling proteins: peptide elicitors (Pep1 and Pep3) and jasmonate acid conjugating enzymes (JAR1a and JAR1b); (ii) maize defensive proteins: the previously identified ribosome-inactivating protein (RIP2) and maize proteinase inhibitor (MPI), and two proteins with predicted but unconfirmed anti-insect activities, an antimicrobial peptide (AMP) and a lectin (JAC1); (iii) lectins from other plant species: Allium cepa agglutinin (ACA) and Galanthus nivalis agglutinin (GNA); and (iv) spider and scorpion toxins: peptides from Urodacus yaschenkoi (UyCT3 and UyCT5) and Hadronyche versuta (Hvt). In most cases, S. frugiperda larval growth on maize was reduced by transient SCMV-mediated overexpression of genes encoding these proteins. Additionally, experiments with some of the SCMV-expressed genes showed effectiveness against two aphid species, Rhopalosiphum maidis (corn leaf aphid) and Myzus persicae (green peach aphid). Together, these results demonstrate that SCMV vectors can be exploited as a rapid screening method for testing the efficacy and insecticidal activity of candidate genes in maize.

Resistance of sorghum hybrids to sorghum aphid

“…The high reproductive rate of this aphid makes in the main pest of sorghum; because it leads to a reduction in productivity caused by the ov of secreted honeydew, which reduces photosynthetic activity, especially by the accumulation of sooty mold on the leaves (Bowling et al, 2016). In addition, the aphid is also a vector of viruses such as: millet red leaf virus (Blackman and Eastop, 1994;Paray et al, 2011), sugarcane yellow leaf virus in sorghum and sugarcane (Schenck and Lehrer, 2000;Boukari et al, 2021) and sugarcane mosaic virus in sorghum (Setokuchi and Muta, 1993;Chung et al, 2021).…”

Getting back to the grass roots: harnessing specialized metabolites for improved crop stress resilience

“…Towards this goal, a modified sugarcane mosaic virus (SCMV) vector was developed in maize for the transient over-expression of defense associated proteins and functional assessment in planta [88]. Potential applications include the expression of non-native genes to explore the production of novel defense chemistries.…”

“…For potato (Solanum tuberosum) root delivery, Bacillus subtilis were recently engineered to secrete StPep1 which significantly reduced galling by the plant pathogenic nematode, Meloidogyne chitwoodi [93 • ]. Similarly, transient expression of ZmPep1 and ZmPep3 via a sugarcane mosaic virus vector activated maize pathways for specialized metabolism and strongly induced resistance against diverse insects [88].…”