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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Insect Genetics and Biochemistry Research » Research » Publications at this Location » Publication #317463

Research Project: INSECT CRYOPRESERVATION, DORMANCY, GENETICS AND BIOCHEMISTRY

Location: Insect Genetics and Biochemistry Research

Title: Variations in thermal history lead to dissynchronous diapause development

Author
item Childers, Anna
item Yocum, George
item Rinehart, Joseph - Joe

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/29/2015
Publication Date: 6/17/2015
Citation: Bennett, A.K., Yocum, G.D., Rinehart, J.P. 2015. Variations in thermal history lead to dissynchronous diapause development [abstract]. Arthropod Genomics Symposium, Kansas State University, June 17-19, 2015Paper. No. 3, page 17.

Interpretive Summary: The alfalfa leafcutting bee, Megachile rotundata, is the world’s most intensively managed solitary bee for commercial pollination. It is the primary pollinator for alfalfa seed production. Managed bees are subjected to thermal regimes for overwintering and subsequent adult emergence in time for alfalfa bloom. Mating, foraging and nesting occurs in the field and larvae develop in brood cells provisioned by the mother. In nature, larval development of the first generation is typically completed by mid-July when a portion of bees undergo diapause, a period of suppressed metabolism and development, and overwinter as prepupa. However, a proportion of the population will avert diapause to produce a second generation, the progeny of which will predominately enter prepupal diapause if they can complete larval development before the onset of winter. Management practices during the prepupal stage affect the physiology of the adult bee and have implications for overwintering survival. Therefore, an understanding of diapause regulation will help improve management practices and enable this bee to be used in additional agricultural markets. Diapausing prepupae produced early and late in the season were removed from nests on September 1, 2010 and divided between two management groups, those kept at a constant 4-5°C and those kept outdoors, exposed to natural temperature fluctuations. Each of these four treatment groups was sampled monthly from October to June. Samples from four time points (November, January, March and May) were chosen to span the diapause maintenance, termination and post-diapause quiescence stages of development. Two lanes of paired-end Illumina sequencing was performed on RNA from three bees from each of the four months (48 samples). Within month treatment comparisons of differentially expressed genes indicates all four treatment groups represent distinct populations, demonstrating the plasticity of the bee’s phenotype in response to their environment. Additionally, while the diapause process synchronizes spring emergence, it does not synchronize the physiology of bees oviposited at different points in the season. Between month treatment comparisons of differentially expressed genes is providing a foundation for understanding the timing of processes regulating diapause development. These results confirm results from studies in other species conducted by ARS scientists in Fargo, ND showing that laboratory studies are necessary, but not sufficient to explain diapause physiology under field conditions. This multi-factorial characterization of M. rotundata diapause will not only aid in commercial management optimization, but will provide insights into mechanisms of quiescence plasticity.

Technical Abstract: The alfalfa leafcutting bee, Megachile rotundata, is the world’s most intensively managed solitary bee for commercial pollination. It is the primary pollinator for alfalfa seed production. Managed bees are subjected to thermal regimes for overwintering and subsequent adult emergence in time for alfalfa bloom. Mating, foraging and nesting occurs in the field and larvae develop in brood cells provisioned by the mother. In nature, larval development of the first generation is typically completed by mid-July when a portion of bees undergo diapause, a period of suppressed metabolism and development, and overwinter as prepupa. However, a proportion of the population will avert diapause to produce a second generation, the progeny of which will predominately enter prepupal diapause if they can complete larval development before the onset of winter. Management practices during the prepupal stage affect the physiology of the adult bee and have implications for overwintering survival. Therefore, an understanding of diapause regulation will help improve management practices and enable this bee to be used in additional agricultural markets. Diapausing prepupae produced early and late in the season were removed from nests on September 1, 2010 and divided between two management groups, those kept at a constant 4-5°C and those kept outdoors, exposed to natural temperature fluctuations. Each of these four treatment groups was sampled monthly from October to June. Samples from four time points (November, January, March and May) were chosen to span the diapause maintenance, termination and post-diapause quiescence stages of development. Two lanes of paired-end Illumina sequencing was performed on RNA from three bees from each of the four months (48 samples). Within month treatment comparisons of differentially expressed genes indicates all four treatment groups represent distinct populations, demonstrating the plasticity of the bee’s phenotype in response to their environment. Additionally, while the diapause process synchronizes spring emergence, it does not synchronize the physiology of bees oviposited at different points in the season. Between month treatment comparisons of differentially expressed genes is providing a foundation for understanding the timing of processes regulating diapause development. These results confirm results from studies in other species conducted by ARS scientists in Fargo, ND showing that laboratory studies are necessary, but not sufficient to explain diapause physiology under field conditions. This multi-factorial characterization of M. rotundata diapause will not only aid in commercial management optimization, but will provide insights into mechanisms of quiescence plasticity.