The Insect Vector, Diaphorina citri Kuwayama Exhibits a Lower Level of Fatty Acids Upon Infection with the Phytopathogenic Bacterium 'Candidatus Liberibacter asiaticus'.

Abstract

Diaphorina citri Kuwayama (Hemiptera: Liviidae) is the main vector for the bacterium 'Candidatus Liberibacter asiaticus', which is associated with citrus greening, also known as Huanglongbing. D. citri transmits 'Ca. L. asiaticus' during its feeding on citrus phloem sap. Transmission occurs in a circulative, propagative, and persistent manner. 'Ca. L. asiaticus' has a small genome (1.2 Mb). Therefore, it acquires most of its nutrients and energetic nucleotides from its hosts. The objective of this study was to assess the effect of 'Ca. L. asiaticus' infection on the level of the free fatty acids in its vector. The fatty acids were extracted from adult D. citri using ethyl acetate, derivatized with boron trifluoride-methanol, and analyzed using gas chromatography-mass spectrometry (GC-MS). Nine fatty acids were identified in the D. citri extracts. Oleic acid was the most predominant fatty acid followed by stearic and palmitic acid, whereas the rest of the fatty acids were present in low amounts. In general, the levels of the detected fatty acids in 'Ca. L. asiaticus'-infected D. citri were lower than those found in healthy psyllids. Our findings showed that, the reduction of fatty acids in 'Ca. L. asiaticus'-infected psyllids resulted from the higher activity of β-oxidation to generate acetyl-CoA, which causes more production of ATP. Our results indicated that 'Ca. L. asiaticus' may enhance the β-oxidation of fatty acids in its vector insect to fulfill its nutrient and energetic nucleotide requirements.