- Author: Kathy Keatley Garvey
(Embargo lifts at 5 a.m. Pacific Time, July 31, 2018)
There they were--odorant receptor genes, the scent-detecting genes thought to have evolved with winged insects more than 400 million years ago. But this groundbreaking discovery indicates they evolved millions of years earlier.
The sensory gene is considered one of an insect's most important genes, crucial to foraging, mating and avoiding predators.
“It was interesting because a paper published in 2014 claimed that ORs evolved with winged flight and were thus absent in ancestrally wingless (Apterygota) insects,” said Brand, a member of the Population Biology Graduate Group who researches the evolution of olfactory/odorant receptor genes in orchid bees. “Since firebrats are apterygote, we now had proof that this gene family is more ancient than previously thought.”
Brand proposed that they merge their datasets and write a comprehensive paper of higher impact rather than two independent papers. It was a “go.”
The collaborative result: “The Origin of the Odorant Receptor Gene Family in Insects,” a newly published paper by a seven-member team from UC Davis, University of Illinois and the University of Tennessee, in the open-access journal eLife, which prints promising research in the life and medical sciences. The article is online at https://doi.org/10.7554/eLife.38340
“Our finding that the odorant receptor gene family evolved at the evolutionary base of the insects makes it a major evolutionary novelty that presumably contributed to the adaptation of early insects to terrestrial living,” Robertson said.
Said Brand: “Odorant receptors are the largest insect gene family underlying the sense of smell. ORs are thus crucial in the majority of behaviors that involve the sense of smell including foraging, reproduction, and detection of predators.” The cell membranes of odorant receptor neurons are key to detecting scents. In insects, the ORs are usually found in the antennae or mouthparts.
In their abstract, the authors wrote that “The origin of the insect odorant receptor (OR) gene family has been hypothesized to have coincided with the evolution of terrestriality in insects. (Christine) Missbach et al. (2014) suggested that ORs instead evolved with an ancestral OR co-receptor (Orco) after the origin of terrestriality and the OR/Orco system is an adaptation to winged flight in insects. We investigated genomes of the Collembola, Diplura, Archaeognatha,
Zygentoma, Odonata, and Ephemeroptera, and find ORs present in all insect genomes butabsent from lineages predating the evolution of insects. Orco is absent only in the ancestrally wingless insect lineage Archaeognatha. Our new genome sequence of the zygentoman firebrat, Thermobia domestica, reveals a full OR/Orco system. We conclude that ORs evolved before winged flight, perhaps as an adaptation to terrestriality, representing a key evolutionary novelty in the ancestor of all insects, and hence a molecular synapomorphy for the Class Insecta.”
Synapomorphy is defined as a characteristic present in an ancestral species and shared exclusively by its evolutionary descendants.
The research is a UC Davis cross-departmental collaboration involving associate professor Brian Johnson of the Davis Department of Entomology and Nematology, Wei Lin of the Johnson lab and a member of the Entomology Graduate Group; and Brand, who studies with major professor Santiago Ramirez of the Department of Evolution and Ecology.
“A recurring theme in the field of genomics is that incomplete sampling of the relevant taxa often leads to premature conclusions,” said Johnson. “Our work on ORs is a good example of this.” Johnson studies the genetics, behavior, evolution, and health of honey bees. His lab currently focuses on the evolution and genetic basis of social behavior using comparative and functional genomics.”
The seven-member team, in addition to the UC Davis and University of Illinois scientists, included a trio from the University of Tennessee: Ratnasri Pothula, William Klingeman, and Juan Luis Jurat-Fuentes.
Brand recalled that he detected the multiple odorant receptor genes in the firebrat genome in late January or early February. “I was working at home after my normal work day, because this genome work I did with Brian was a side project for me—he knew of my interest in genomics and offered me the opportunity to collaborate on his lab's ongoing projects.”
Brand expects to receive his doctorate from UC Davis in the spring of 2019. A native of Germany and a former research scientist at Ruhr-University, Bochum, he received his master's degree in genetics and evolutionary biology in 2013 from Ruhr-University, and his bachelor's degree in biology in 2010 from Heinrich-Heine University, Düsseldorf, Germany.
Winged insects first appeared on earth 406 million years ago, according to research published in a 2014 edition Science by molecular biodiversity researcher Bernhard Misof, a professor at the University of Bonn, Germany.
Fossil records indicate that hexapods diverged from crustaceans 410 to 510 million years ago, according to Misof. “At this time in geological history, land masses were dotted with shallow inland seas, and plant life (mostly algae and bryophytes) was largely restricted to coastal habitats and other sites where water was readily available,” according to a North Carolina State University's Department of Entomology website. “The oldest hexapod fossils are found in rocks of the late Devonian period. These rocks also contain numerous other terrestrial arthropods (mites, spiders, centipedes, scorpions, etc.) suggesting that a major radiation of terrestrial life-forms must have occurred during the Ordovician or Silurian period.”
The first known fossil record of Apterygota insects, which include firebrats, silverfish and jumping bristletails—dates back to the Devonian period, which began 417 years ago.
The firebrat, found throughout the world under rocks and leaf litter, is an indoor pest of dog food, stored foods, fabric and book bindings. It is commonly found in high-humidity environments such as bakeries and boiler rooms.
According to the UC Statewide Integrated Pest Management Program (UC IPM), both firebrats and their cousin silverfish “have enzymes in their gut that digest cellulose, and they choose bookcases, closets, and places where books, clothing, starch, or dry foods are available. Silverfish and firebrats are nocturnal and hide during the day. If the object they are hiding beneath is moved, they will dart toward another secluded place. They come out at night to seek food and water. Both insects prefer dry food such as cereals, flour, pasta, and pet food; paper with glue or paste; sizing in paper including wallpaper; book bindings; and starch in clothing. Household dust and debris, dead insects, and certain fungi also are important sources of food. However, they can live for several months without nourishment.”
“Large numbers of these insects can invade new homes from surrounding wild areas, especially as these areas dry out during the summer,” the UC IPM website says. “They also can come in on lumber, wallboard, and similar products. Freshly laid concrete and green lumber supply humidity, while wallpaper paste provides food.”
Resources:
eLife: https://doi.org/10.7554/eLife.38340
UC IPM Pest Note on Firebrat: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7475.html
Information on hexapods: https://genent.cals.ncsu.edu/bug-bytes/hexapods/
Philipp Brand website: https://evolvingors.wordpress.com
Contacts:
Philipp Brand: pbrand@ucdavis.edu
Brian Johnson: brnjohnson@ucdavis.edu
Hugh Robertson: hughrobe@uiuc.edu
- Author: Kathy Keatley Garvey
The non-profit educational organization, geared for small-scale beekeepers in the western United States, is headed by president Eric Mussen, Extension apiculturist emeritus, of UC Davis.
WAS has already booked Kim Flottum of Medina, Ohio, editor of Bee Culture; Les Crowder of Austin, Texas, author of Top-Bar Beekeeping; Gene Brandi of Los Banos, president of the American Beekeeping Federation; Larry Connor of Kalamazoo, Mich., author and beekeeper; Rod Scarlett, executive director, Canadian Honey Council, and Slava Strogolov, chief executive officer of Strong Microbials Inc., Milwaukee.
- Extension apiculturist Elina Lastro Niño will speak on “Impact of Varroa on Honey Bee Reproductive Castes): Where Will the Research Lead Us?” at at 8:30 a.m. The three reproductive castes are the queen and worker bee (female), and drone (male).
- Associate professor Brian Johnson will speak on “Geographical Distribution of Africanized Bees in California” at 9 a.m., He will show “the results of a genotyping study of bees caught from across California showing the current distribution of Africanized Honey Bees in our state."
- Distinguished emeritus professor Robbin Thorp, a native pollinator specialist, will discuss “Life Cycles of Commonly Encountered Native Bee Genera" at 10:30 a.m. He is the co-author of Bumble Bees of North America: an Identification Guide and California Bees and Blooms: A Guide for Gardeners and Naturalists.
- Professor Neal Williams, a pollination ecologist, will discuss “Known and Potential of Native Bees in Crop Pollination” at 11 a.m.
Casey also will lead a tour of the haven at 9:30 a.m. on Wednesday, Sept. 6. “The Haven is a unique outdoor museum designed to educate visitors about bees and the plants that support them," she says. "Tour participants will see some of our 85 bee and 200 plant species, learn about our outreach and research programs, and gain ideas for their own bee gardens." Other tours are to Mann Lake facility and Z Specialty Foods, both in Woodland.
On Friday, Sept. 8, Extension apiculturist emeritus Eric Mussen will moderate a panel on “Pesticide Toxicity Testing with Adult and Immature Honey Bees.” The panel will convene at 9:15 a.m. At 1:30 on Friday, assistant professor Rachel Vannette of UC Davis will discuss “Variation in Nectar Quality Influence Pollinator Foraging." She studies floral nectar chemistry and microbiology and examines how these characteristics of flowers mediate interactions between plants and pollinators
Other UC Davis highlights:
Honey Tasting: Amina Harris, director of the Honey and Pollination Center at the Robert Mondavi Institute of Wine and Food Science, UC Davis, will lead a moderated honey tasting at 11 a.m. on Wednesday, Sept. 6. The event is titled “Taste the Honey Flavors of the West: How Understanding the Nuances of your Honey Can Help You Market your Perfect Sweet.” Said Harris: "Basically I plan to discuss the diversity and life styles of non-Apis bees to show how different most are from honey bees."
Memories: The founders of WAS will discuss "how it all began" from 8:45 to 9:30 a.m. on Wednesday, Sept. 6. The organization, founded at UC Davis, was the brainchild of Norm Gary, then professor of apiculture (now emeritus), who served as the first WAS president. Assisting him in founding the organization were Eric Mussen, then an Extension apiculturist who was elected the first WAS vice president; and postdoctoral fellow Becky Westerdahl, now a nematologist in the department, who held the office of secretary-treasurer.
More information on the conference is available from the WAS website or contact Eric Mussen, serving his sixth term as president, at ecmussen@ucdavis.edu. Registration is underway at http://www.westernapiculturalsociety.org/2017-conference-registration/
- Author: Kathy Keatley Garvey
As an undergraduate at the University of Illinois, Urbana-Champaign, he enrolled in an introductory entomology class. “I remember seeing the research technician standing in and indoor flight cage, surrounded by bees,” Nye said. “They were flying from the hive to a feeder stand and completely ignoring her. We covered the long history of beekeeping in that class around that same time and I was just amazed at how much knowledge had been collected. I applied for a job and started working as an assistant to the research technician I saw that day that spring. I spent the next three summers working for the lab of Dr. Gene Robinson and learning as much as I could.”
He went on to spend eight years in Illinois working with the bees—three as an undergraduate assistant and five years as the facility manager and research technician. He joined UC Davis in December 2015.
“Adapting to the California ecosystem has been a bit of an adjustment,” Nye said. “A big part of beekeeping is understanding the ecosystem you live in. If you've got a bee yard that doesn't have a water source close, you may need to move water in during dry periods. Different flowers provide nectar and pollen at varying quantities, so being aware of what's going on in the environment can give you some insight into whether or not you might need to assist your bees with some sugar to make it until the next bloom. That has honestly been my favorite part of moving here, learning about all the trees and shrubs and wildflowers and when they bloom. It's a constant process through the year, and being my first year here it's been really enjoyable to watch the seasons progress."
Nye welcomes the worldwide interest in bees and the crucial role they play. “I think people are starting to understand the complex role bees play in our food system, and I hope in the future we could help educate people about how the agricultural system is helped by natural areas,” he said. “Here in the Central Valley, there is very little unused space. We are able to bring in honey bees on trucks from distant areas to pollinate our crops, but it's a very precarious system that we are relying on to make that work. Having some natural corridors for pollinators year round would really help increase the population of native bees, help the health of honey bees, and keep us from worrying about losing the delicate balance we are keeping between honey bees and agricultural production.”
"I think the general public's knowledge of bees has made amazing advances in recent years. The shortage of bees for agricultural purposes here in the Central Valley really brought beekeeping into the news, followed by a lot of documentaries and things that made people want to be beekeepers or at least plant pollinator friendly gardens. Lots of people bring up beekeeping documentaries they've seen, and I don't think beekeepers were experiencing that 20 years ago. Overall, I'm mostly impressed with the amount of bee related knowledge out in the world right now.
Myths and misconceptions about bees? Often people associate bees with stinging, and falsely claim they have an allergy. “I've been doing this long enough that I don't laugh at people when they tell me they are allergic, but I think people don't completely understand what allergic means,” he said. “Only one or two people out of 1000 are actually allergic and have a life threatening reaction--most people just experience pain and swelling. I try to point out to people that when it hurts and makes their hand swell up, that might not mean they have a bee allergy, but most of the time I just nod my head and move on. I worked a booth at a local fair and half my conversations were people telling me they were allergic because it hurt. I get stung every day, and I can attest that at no point does it stop hurting.”
Nye divides his time with the labs of Extension apiculturist Elina Niño, pollination ecologist Neal Williams, and Brian Johnson, who studies the behavior, evolution and genetics of honey bees. “My responsibilities are pretty spread out,” he said. “The majority of my time is spent keeping the bees healthy enough for experiments.” In peak season, “it's pretty common to just have a few weeks' notice that we need any number of healthy full sized colonies, and like other animals, you can't grow a calf to a full sized cow with any magic tricks, so we try to buffer that by keeping a tight schedule for disease monitoring and making sure all our colonies are as robust as possible.”
What does he like the best about his job? The least?
"My job has a great balance between working out in a natural setting going through bee hives, and coming back to the lab and getting involved in research," he said. "I think doing either one of them by themselves would get a little tedious for me, so I feel really lucky to be able to split myself between the two. The least? It might be kind of a strange complaint, but foxtails. I spend a lot of time walking through tall grass and those foxtails burrow into my shoes and make me crazy. And I'm told I have to worry about them going up my dog's nose? I would say it's an urban myth but the seeds ability to get into my shoe and under my sock is practically magic."
(Editor's Note: For a list of the 2017 apiculture courses that the Niño lab is offering and teaching, see this page.)
- Author: Kathy Keatley Garvey
(Editor's Note: An update: The results of the CDFA analysis have been announced. The maternal lineage of the problematic colony in Concord was European. "Therefore, if that queen's daughters were acting in a very Africanized manner, it might have been because she mated with Africanized drones in the area," said Extension apiculturist emeritus Eric Mussen, "or because there are a number of drones from European cantankerous colonies around the area. The paternity tests were not run.")
It's all the buzz.)
For the past several days, journalists have sought out UC Davis experts Extension apiculturist Elina Niño and Extension apiculturist (emeritus) Eric Mussen to weigh in on the recent defensive bee incident in Concord.
The three-day incident began Friday, May 13, and primarily ended on Sunday, when many of the bees were destroyed. What happened: A beekeeper on Hitchcock Road was moving his two hives to make way for landscaping in his yard. He moved the first hive successfully, but the bees in the second hive turned defensive, killing two dogs, attacking a mail carrier, and targeting numerous passersby.
DNA tests are underway to see if the bees are Africanized. “Their behavior is very suggestive that they could be Africanized,” Mussen said.
Niño, who joined the UC Davis Department of Entomology and Nematology in September 2014, replacing Mussen, was interviewed by the Associated Press, San Francisco and Kathy Park of KXTV Channel 10 and Tom Jensen of KCRA Channel 3. More interviews are pending.
Mussen, who completed a 38-year career in 2014 and now serves as emeritus, was quoted in the San Francisco Chronicle and in other news media.
Niño told KCRA "Africanized honey bees tend to be more defensive, they amount a stronger defensive response. First of all, we don't like to call them killer bees. That's definitely not what they're there for. They're not coming at you for no reason."
Mussen told the San Francisco Chronicle that attempts to avoid the bees may have actually made things worse. Waving arms and swatting motions can provoke bees to sting — and then the stings themselves act as markers for other bees to target, he said.
Africanized bees are a hybrid of African honey bees and European/Western honey bees. In the 1950s, Brazilian scientists exported bees from South Africa to improve breeding stock and increase honey production. However the bees escaped quarantine and began mating with European honey bees. Since they they have spread throughout South and Central America and arrived in North America in 1985. Africanized bees expanded into southern California in 1994.
In appearance, Africanized bees and European honey bees look alike and cannot be distinguished except through DNA tests, Niño and Mussen said.
Mussen says that we have three ways to try to differentiate between Africanized honey bees (AHBs) and European honey bees (EHBs):
1. Mitochondrial DNA – The California Department of Food and Agricuture (CDFA) still conducts this type of testing once a year to clear the California Bee Breeders for queen exports into Canada. CDFA also uses this criterion as "the one" for declaring Africanization. However, its value in predicting temperament of the colony population is not particularly reliable.
2. Isozymes - the amino acid composition of certain enzymes differs between the two races
3. Morphometrics - computer matching of current sample specimens to verified AHB and EHB samples using measurements of various anatomical features. Hybrids are problematic.
"That type of bee was found around southern California and as far north as not too far from Angles Camp (Calaveras County)," Mussen mentioned. "Further north, they found only specimens with one or two traits, but not all three. That even occurred just into southern Oregon."
“Yes, EHB colonies can behave in that nasty manner, but I think it is more likely that AHBs are involved,” Mussen says. He recalled that twice in the 1980s, swarms of bees from South America accompanied shipments of raw sugar cane into the C&H sugar refinery in Crockett (Contra Costa County). We know the first one got away. They think they got the second one, but could not find the queen in either case. Since that time, there have been increasing complaints of 'hot' bees from that area, south to Castro Valley (Alameda County).”
Assistant professor Brian Johnson of the UC Davis Department of Entomology and Nematology, is doing research on genetic dispersion of AHBs around the state. He is collecting and freezing samples.
- Author: Kathy Keatley Garvey
The paper on bee immunity and toxin metabolism was published Nov. 9 in Scientific Reports, part of the Nature Publishing Group.
“First, the results suggest that forager bees may use antimicrobial peptides—short sequences of amino acids with general activity-- to reduce microbial growth in stored food resources,” said Rachel Vannette of the UC Davis Department of Entomology and Nematology. “This would be a largely unrecognized way that bees protect honey and potentially other stored resources from microbial spoilage. Second, this work shows that forager bees produce toxin-degrading enzymes in nectar-processing tissues.”
“This may allow forager bees to degrade many different kinds of compounds in nectar, before it is stored,” Vannette said. “Bees also vary in their ability to do this—foragers have a greater ability to degrade a variety of compounds than nurses. This may have implications for hive health and management.”
"Nice paper,” said Gene Robinson, director of the Institute for Genomic Biology and Swanlund Chair of Entomology, University of Illinois at Urbana-Champaign, who was not involved in the research. “It had been well known that the division of labor in a honey bee colony is supported by extensive differences in brain gene expression between bees that perform different jobs. This new research shows nicely that this genomic differentiation extends beyond the brain; different complements of active genes in a variety of tissues make each bee better suited for the job it needs to perform."
The journal article, titled “Forager Bees (Apis mellifera) Highly Express Immune and Detoxification Genes in Tissues Associated with Nectar Processing,” is the work of senior author/assistant professor Brian Johnson of the UC Davis Department of Entomology and Nematology, and co-authors Abbas Mohamed, graduate student researcher in the Johnson lab and a member of the Pharmacology and Toxicology Group, and assistant professor Vannette, who joined the UC Davis Department of Entomology this fall after serving a postdoctoral fellowship at Stanford University. At Stanford, Vannette examined the role of nectar chemistry in community assembly of yeasts and plant-pollinator interactions.
Johnson, whose research interests include animal behavior, evolution, theoretical biology and genomics, recently began long-term research on the honey bee immune system and the causes and consequences of economically important diseases /syndromes such as colony collapse disorder.
Mohamed, who has researched honey bees since 2011, is currently focusing on pesticide detoxification as a part of his master's degree research. "Honey bees have always fascinated me,” Mohamed said, “and there is nothing more exciting than to be at the edge of discovery, learning new things, and contributing to the field of our understanding of these amazing creatures.”
The team plans to follow up with functional assays to examine the potential of these gene products to (1) reduce microbial growth and (2) degrade a variety of natural and synthetic compounds.
The abstract:
“Pollinators, including honey bees, routinely encounter potentially harmful microorganisms and phytochemicals during foraging. However, the mechanisms by which honey bees manage these potential threats are poorly understood. In this study, we examine the expression of antimicrobial, immune and detoxification genes in Apis mellifera and compare between forager and nurse bees using tissue-specific RNA-seq and qPCR. Our analysis revealed extensive tissue-specific expression of antimicrobial, immune signaling, and detoxification genes. Variation in gene expression between worker stages was pronounced in the mandibular and hypopharyngeal gland (HPG), where foragers were enriched in transcripts that encode antimicrobial peptides (AMPs) and immune response. Additionally, forager HPGs and mandibular glands were enriched in transcripts encoding detoxification enzymes, including some associated with xenobiotic metabolism. Using qPCR on an independent dataset, we verified differential expression of three AMP and three P450 genes between foragers and nurses. High expression of AMP genes in nectar-processing tissues suggests that these peptides may contribute to antimicrobial properties of honey or to honey bee defense against environmentally-acquired microorganisms. Together, these results suggest that worker role and tissue-specific expression of AMPs, and immune and detoxification enzymes may contribute to defense against microorganisms and xenobiotic compounds acquired while foraging.”