Annotation and analysis of yellow genes in Diaphorina citri, vector for the Huanglongbing disease

Huanglongbing (HLB), also known as citrus greening disease, is caused by the bacterium Candidatus Liberibacter asiaticus (CLas) and represents a serious threat to global citrus production. This bacteria is transmitted by the Asian citrus psyllid, Diaphorina citri (Hemiptera) and there are no effective in-planta treatments for CLas. Therefore, one strategy is to manage the psyllid population. Manual annotation of the D. citri genome can identify and characterize gene families that could serve as novel targets for psyllid control. The yellow gene family represents an excellent target as yellow genes are linked to development and immunity due to their roles in melanization. Combined analysis of the genome with RNA-seq datasets, sequence homology, and phylogenetic trees were used to identify and annotate nine yellow genes for the D. citri genome. Phylogenetic analysis shows a unique duplication of yellow-y in D. citri, with life stage specific expression for these two genes. Genomic analysis also indicated the loss of a gene vital to the process of melanization, yellow-f, and the gain of a gene which seems to be unique to hemipterans, yellow 9. We suggest that yellow 9 or the gene yellow 8 (c), which consistently groups closely to yellow-f, may take on this role. Manual curation of genes in D. citri has provided an in-depth analysis of the yellow family among hemipteran insects and provides new targets for molecular control of this psyllid pest. Manual annotation was done as part of a collaborative community annotation project (https://citrusgreening.org/annotation/index).