Novel tephritid-specific features revealed from cytological and transcriptomic analysis of Anastrepha ludens embryonic development

Abstract

Anastrepha ludens is a major pest of fruits including citrus and mangoes in Mexico and Central America with major economic and social impacts. Despite its importance, our knowledge on its embryonic development is scarce. Here, we report the first cytological study of embryonic development in A. ludens and provide a transcriptional landscape during key embryonic stages. We established 17 stages of A. ludens embryogenesis that closely resemble the morphological events observed in Drosophila. In addition to the extended duration of embryonic development, we observed notable differences including yolk extrusion at both poles of the embryo, distinct nuclear division waves in the syncytial blastoderm and a heterochronic change during the involution of the head. Characterization of the transcriptional dynamics during syncytial blastoderm, cellular blastoderm and gastrulation, showed that approximately 9000 different transcripts are present at each stage. Even though we identified most of the transcripts with a role during embryonic development present in Drosophila, including sex determination genes, a number of transcripts were absent not only in A. ludens but in other tephritids such as Ceratitis capitata and Bactrocera dorsalis. Intriguingly, some A. ludens embryo transcripts encode proteins present in other organisms but not in other flies. Furthermore, we developed an RNA in situ hybridization protocol that allowed us to obtain the expression patterns of genes whose functions are important in establishing the embryonic body pattern. Our results revealed novel tephritid-specific features during A. ludens embryonic development and open new avenues for strategies aiming to control this important pest.