Monday, December 11, 2006

Respirometry, differential gene expression, and histological studies on sugarbeet root maggot larvae in long-term storage

Anitha Chirumamilla,, North Dakota State University, Department of Entomology, 1300 Albrecht Blvd, Hultz Hall, room 202, Fargo, ND, George Yocum,, USDA-ARS, Insect Genetics and Biochemistry Research Unit, Biosciences Research Lab, 1605 Albrecht Blvd, Fargo, ND, and Mark A. Boetel,, North Dakota State University, Entomology, 202 Hultz Hall, Fargo, ND.

Mature 3rd-instar sugarbeet root maggots, starting as diapausing larvae have a remarkable ability to survive more than 5 years in laboratory storage at 5-7 degrees Celsius. To test the hypothesis that this long term survival in storage is facilitated by larvae continuing in the state of diapause, comparative studies on respiration rates, gene expression analyses, and histological assessments were conducted by comparing field-collected diapausing larvae (November and December) and laboratory stored larvae that had been maintained in cold storage for 1, 2, 4, and 5 years. Laboratory stored larvae had similar rates of respiration as that of field-collected diapausing larvae when measured at 5 and 20 degrees Celsius. A 15-degree rise in temperature elevated the overall respiration in both diapausing as well as stored larvae with a higher increase in carbondioxide production levels, 8-44 times higher than at 5 degrees Celsius, when compared to a 6-10 fold increase in oxygen consumption levels. Increasing temperatures caused a major shift in respiratory quotient values from 0.5 to approximately 1.0, in 5-year old larvae and diapausing larvae collected from the field in December, with only minor changes in rest of the groups. A transcript for alcohol dehydrogenase (Adh) was identified via differential display in diapausing and stored larvae. Adh is expressed in diapausing larvae but was absent in 1-, 2-, and 5-year old larvae in storage. Histological evaluations aimed at comparing the brain tissues of short- and long-term-stored larvae using transmission electron microscopy are in progress and will be presented.

Species 1: Diptera Olidiidae Tetanops myopaeformis (sugarbeet root maggot)