In silico secretome prediction and expression analysis of potential effector candidates of fall armyworm (Spodoptera frugiperda)

Abstract

Effector proteins, one of the major insect salivary gland components, alter host defence mechanism(s) and facilitate pests for successful infestation of host plant. Fall armyworm, Spodoptera frugiperdais a polyphagous lepidopteran insect infesting a wide range of agricultural crops. Despite being one of the world’s deadliest pests, no information about the effector proteins of S. frugiperda is available, till date. Therefore, in this study, we have performed an in silico analysis of interproscan-annotated protein sequences of S. frugiperda (derived from its transcriptome) using established secretome prediction pipelines. Out of 21,779protein sequences of S. frugiperda, 821 proteins were predicted to be secretory in nature, leading to the generation of an in silico secretome database of S. frugiperda. The proteins of S. frugiperda secretome were categorised into different functional groups as per their annotated functions. The expression of 40 selected candidates was analysed in different tissues (head, gut, salivary gland and fat body) of S. frugiperda, which revealed 14 candidates to be exclusive to a single tissue. In addition, expression of 13 candidates were found to be exclusive to gut or salivary glands or to both the tissues indicating that they may be secreted out from the insect's body and serve as potential effector proteins. The study described here is the first report of S. frugiperda's secretome prediction which will help in the identification of candidates which are secretory in nature, ultimately opening the door to the identification of possible effector proteins of S. frugiperda.