Knocking out the caleosin-encoding gene GmCLO1 improves soybean resistance to common cutworm.

Abstract

The jasmonic acid (JA) pathway is central for plant defence against herbivores, and genes related to this pathway have received increased attention. Here, we evaluated the functions of the allene oxide cyclase (AOC)-encoding gene GmAOC3 and the caleosin-encoding gene GmCLO1, which may affect JA synthesis in soybean, and explored the anti-insect mechanisms of these two genes. The overexpression of GmAOC3 increased soybean resistance to the common cutworm (CCW). The strongest resistance to CCW was observed in the GmAOC3-overexpressing line GmAOC3-OE-1. Whole-genome resequencing and expression analysis revealed that in this line, GmCLO1 silencing was caused by insertion of the GmAOC3 gene into the GmCLO1 sequence. GmCLO1 expression responded to CCW induction. Compared with the controls, the knockdown or knockout of GmCLO1 increased soybean resistance to CCW. Conversely, the overexpression of GmCLO1 decreased CCW resistance. Transcriptomic and metabolomic analyses revealed that the gmclo1-knockout line shared 653 differentially expressed genes (DEGs) and 87 differentially abundant metabolites with the GmAOC3-OE line. Among these common DEGs, anti-insect genes related to JA, such as the 9-lipoxygenase gene Glyma.13G347800, the vegetative storage protein gene Glyma.08G200100, and the trypsin inhibitor gene Glyma.06G219900, showed upregulated expressions in both lines. Additionally, JA and JA-isoleucine contents were notably elevated in the GmAOC3-OE-1 line but decreased in the GmCLO1-overexpressing line. Measurements of yield-related traits revealed that GmAOC3 overexpression and/or GmCLO1 knockout did not affect soybean yield. In conclusion, we identified two new target genes for insect-resistant soybean breeding and contributed to an in-depth understanding of the JA-mediated insect resistance mechanisms in soybeans.