Gene expression, proteomic, and metabolic profiles of Brazilian soybean genotypes reveal a possible mechanism of resistance to the velvet bean caterpillar Anticarsia gemmatalis

Brazil is the world’s largest producer of soybeans, and the crop is one of the most important contributors to the economy. Soybeans often suffer damage from insect pests, such as Anticarsia gemmatalis, which also attacks other crops. Genotypes of soybeans have been used to decipher the resistance mechanisms by evaluating the activity of defense compounds such as protease inhibitors (PIs) and flavonols. However, the genetic determinants of resistance have not been thoroughly investigated. This study used the response of resistant and susceptible genotypes of soybean to evaluate genes and proteins responsive to caterpillar attack and involved in the biosynthesis of methylated and glycosylated flavonols. Rutin and isorhamnetin rutinoside were produced constitutively in the resistant genotypes IAC 17 and IAC 100. Following insect attack, genes encoding flavonol synthase and methyltransferases were highly upregulated in IAC 17. Some herbivory defense responses appear constitutive, while others were induced or JA-independent, as verified for flavonol levels. Salicylic acid levels were higher in IAC 17 and IAC 100. Proteins not yet characterized for their involvement in plant–insect interactions, such as transmembrane receptors and transcription factors, were upregulated in the resistant genotype IAC 17. It appears constitutive flavonol biosynthesis in both IAC 17 and IAC 100 was inherited from the PI229358 parent, making the two genotypes good genetic sources to study flavonol biosynthesis and their relationship with insect resistance.