CYP4AB1, CYP4AB2, and Gp-9 gene overexpression associated with workers of the red imported fire ant, Solenopsis invicta Buren.

Abstract

Two cytochrome P450 genes, CYP4AB1 and CYP4AB2, and the Gp-9 gene were identified as being specifically overexpressed in workers of the red imported fire ant using PCR-selected subtractive hybridization and cDNA array techniques. Full-length CYP4AB1 and CYP4AB2 were cloned and sequenced. The cDNA sequences of CYP4AB1 and CYP4AB2 have open reading frames of 1389 and 1533 nucleotides encoding proteins of 463 and 511 amino acid residues, respectively. Northern blot analysis was performed to compare expression levels of CYP4AB1, CYP4AB2, and Gp-9 for different developmental stages and castes of fire ants. We demonstrate that the expression of these three genes is developmentally and caste specifically regulated in red imported fire ants. Levels of CYP4AB1 mRNA were undetectable in 3rd+4th instars, worker pupae, and alate (mixed sex) pupae; readily detectable in male and female alates; increased (approximately 3-fold) in the queens; and rose to a maximum (13-fold) in workers. Similarly, the expression of CYP4AB2 mRNA was undetectable in 3rd+4th instars, worker pupae, and alate pupae; low in male and female alates and queens; and increased (approximately 7-fold) in workers. Levels of Gp-9 mRNA were readily detectable in male alates; increased (approximately 3-fold) in female alates; and reached a maximum (approximately 12-fold) in workers. Their caste-specific overexpression suggests the functional importance of CYP4AB1, CYP4AB2, and Gp-9 in workers of the red imported fire ant.