Immune Gene-linked EST-SSR Marker Development for Coconut Scale Insects, Aspidiotus Destructor Signoret and Aspidiotus Rigidus Reyne

Abstract

Abstract The infestation of coconut scale insects (CSI), Aspidiotus destructor and A. rigidus, resulted in significant economic damages to the Philippine coconut industry in recent years. This incident demands a thorough understanding of the biological information of the insect pests to understand how they thrive and perpetuate despite of adverse ecological conditions. This research explored microsatellite mining, characterization, and marker design on two species of coconut scale insect. Using bioinformatics approaches, predominant dinucleotide repeats units (TA and TC), average length of 40bp and density of 728 SSRs/Mbp were observed in the microsatellite regions of the transcriptomes. A total of 18,480 and 1,681 EST-SSR markers were designed for A. destructor and A. rigidus, respectively. In addition, homology search of 4,369 immune genes from 4IN database against the transcriptome assemblies revealed 22 and 302 orthologs expressed by A. rigidus and A. destructor, respectively. This result provides insights into the expression of genes involved in evolutionarily conserved immune pathways (i.e.,Toll, Imd, JNK, and JAK- STAT) of these two coconut scale insect species. From the vast resource of EST-SSR markers, eight (8) immune gene-linked EST-SSR markers were deduced targeting effete (eff), autophagy 8 (Atg8), ras-like GTP-binding protein (rho1) and anterior open (aop). The polymorphic EST-SSR markers established in this research can be used for comprehensive genetic analysis of coconut scale insects towards safeguarding the country's vibrant coconut industry.