Transcriptional Analysis of Microsatellites in Velvetbean Caterpillar Anticarsia gemmatalis Hübner, 1818

Abstract

Brazil is the largest producer of soybeans in the world. The vast extent of soybean plantations across the Brazilian territory exposes this crop to attack by several insects, including the velvetbean caterpillar, <i>Anticarsia gemmatalis</i>. One of the alternatives used to control this insect are the toxins produced by <i>Bacillus thuringiensis</i> (<i>Bt</i>). However, in some cases, resistance to these toxins has been reported in the laboratory. Despite the ecological and economic impact of the velvetbean caterpillar, there are few studies on the genetic structure of this species, especially with regard to microsatellites. In this paper, we carried out a comparative transcriptional analysis of microsatellites in resistant (RES) and susceptible (SUS) strains of <i>A. gemmatalis</i> challenged and not challenged with <i>Bt</i> toxins. According to the number of sequences analyzed in each group, a 7.9% simple sequence repeat (SSR) rate was identified for the SUS library, and 7.4% for SUS<i>Bt</i>. For the RES group, this value was 8.5% and for the RES<i>Bt</i> 7.7%. Most of the fragments found showed a shorter repeat pattern, located in mono- and trinucleotide motifs. Among the 128 types of SSR motifs, it was possible to notice a large amount of adenine and thymine in relation to guanine and cytosine, which was also seen in chromosomes after staining with base-specific fluorochromes DAPI/CMA<sub>3</sub>, highlighting DAPI-positive regions. Although the participation of microsatellites in the resistance mechanism of <i>A. gemmatalis</i> to <i>Bt</i> is not clear, the results obtained in this work contribute to a better understanding of the repetitive DNA found in transcribed regions of a non-model organism.