Annotation of glycolysis, gluconeogenesis, and trehaloneogenesis pathways provide insight into carbohydrate metabolism in the Asian citrus psyllid

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Citrus greening disease is caused by the pathogen Candidatus Liberibacter asiaticus, which is transmitted by the Asian citrus psyllid, Diaphorina citri . There is no curative treatment or significant prevention mechanism for this detrimental disease that causes continued economic losses from reduced citrus production. A high quality genome of D. citri is being manually annotated to provide accurate gene models required to identify novel control targets and increase understanding of this pest. Here, we annotated genes involved in glycolysis, gluconeogenesis, and trehaloneogenesis in the D. citri genome, as these are core metabolic pathways and suppression could reduce this pest. Specifically, twenty-five genes were identified and annotated in the glycolysis and gluconeogenesis pathways and seven genes for the trehaloneogenesis pathway. Comparative analysis showed that the glycolysis genes in D. citri are highly conserved compared to orthologs in other insect systems, but copy numbers vary in D. citri .

Expression levels of the annotated gene models were analyzed and several enzymes in the glycolysis pathway showed high expression in the thorax. This is consistent with the primary use of glucose by flight muscles located in the thorax. A few of the genes annotated in D. citri have been targeted for gene knockdown as a proof of concept, for RNAi therapeutics. Thus, manual annotation of these core metabolic pathways provides accurate genomic foundations for developing gene-targeting therapeutics to reduce D. citri .

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  1. Abstract

    A version of this preprint has been published in the Open Access journal GigaByte (see paper, where the paper and peer reviews are published openly under a CC-BY 4.0 license.

    **Reviewer 1. Mary Ann Tuli **

    Are all data available and do they match the descriptions in the paper? No. The paper states "The D. citri genome assembly (v3), OGS (v3) and transcriptomes are accessible on the portal" I believe v2 is available, not v3 yet.

    Additional Comments The paper states "The gene models will be part of an updated official gene set (OGS) for D. citri that will be submitted to NCBI." Until these models are available in NCBI their reuse is limited.

    Recommendation: Minor Revision

  2. Citrus greening disease

    **Reviewer 2. Xinyu Li **

    In the paper entitled “Annotation of glycolysis, gluconeogenesis, and trehaloneogenesis pathways provide insight into carbohydrate metabolism in the Asian citrus psyllid”, the authors conducted a high quality annotation of genes involved in glycolysis, gluconeogenesis, and trehaloneogenesis in Diaphorina citri genome, which provided the bases to develop gene-targeting therapeutics for this important pest species.

    The MS is well-written, and the analyses are clear and proper. I found some minor concerns that should be addressed.

    In the first paragraph of Page 10, the authors used cross symbol and the asterisk in the sentence “The number of genes identified in glycolysis….from NCBI, OrthoDB, and Flybase.”. However, the cross symbol and the asterisk are used without any explanation or citation. I suggest to cite the Appendix the authors referred to or add an explanation to make it clearer.

    In Conclusion part, on Page 15, the authors stated “Expression analysis of the genes annotated in the carbohydrate metabolism pathways identified differences related to life stage, sex and tissue.”. But what are the differences are not mentioned here. I think it would be better to summarize the key/predominant differences about gene expression in the carbohydrate metabolism pathways.

    In addition, it is interesting that the gene expression related with carbohydrate metabolism is sexually different in the Asian citrus psyllid. Is it common in insects or existed in some specific groups?