Data released on April 19, 2017
Invasive whitefly, Bemisia tabaci, is a highly destructive agricultural and ornamental crop pest. As a group, B. tabaci damages host plants through phloem feeding and vectoring plant pathogens. Introductions of B. tabaci are difficult to quarantine and eradicate due to high reproductive rates, broad host plant range, and resistance to chemical insecticides. A 658 Mb draft genome for the Q-type B. tabaci (MED/Q) assembled and annotated with 20,786 protein-coding genes. Metabolic pathways show an expansion in the number of gene family members, in particular, the cytochrome P450 monooxygenases. Additionally, amino acid biosynthesis pathways are partitioning among host and endosymbiont genomes in a manner that is distinct from other hemipteran systems, wherein evidence of horizontal gene transfer to the host genome likely form the basis of obligatory relationships. Putative loss of function of the immune deficiency (IMD) signaling pathway due to gene loss is a shared ancestral trait of hemipteran insects that show competency for hosting endosymbiotic bacteria. This expansion of P450 gene family member may influence the well-noted capacity of MED/Q to adapt to repeated exposures to chemical insecticides, and furthermore, be related to invasiveness in monoculture cropping systems where such applications are prevalent.
This sequencing project was a collaborative effort between BGI-shenzhen and a consortium of international whitefly researchers. Various members have corresponded extensively through e-mails and phone calls. Many aspects of the genome sequencing project were discussed including the choice of B. tabaci cryptic species to propose. The researchers collectively decided that given the many resources already developed, the global invasion status and the large number of scientists studying them, the Q-type B. tabaci (MED/Q) would be the best choice. We expect that fairly extensive studies can be undertaken on other cryptic species of B. tabaci through the use of heterologous sequences once the B. tabaci Q genome sequence is available.