New clues to how the bacteria associated with citrus greening infect the only insect that carries them could lead to a way to block the microbes' spread from tree to tree, according to a study in Infection and Immunity by scientists at Boyce Thompson Institute (BTI) and the Agricultural Research Service (ARS).
Citrus greening, also known as huanglongbing, is a serious disease dramatically affecting citrus production all over the world. Trees with this disease are unable to get enough nutrients from the soil, their leaves turn yellow, young twigs die back, and fruit remains small, green and unsuitable for sale. After only a few years the trees die completely.
These symptoms are associated with a bacterium called 'Candidatus Liberibacter asiaticus,' referred to as CLas for short, which is spread from tree to tree by its tiny insect vector, the Asian citrus psyllid (Diaphorina citri). Today, citrus greening has been detected in every citrus-producing county in Florida, throughout the southern citrus growing states and in isolated spots of southern California. Growers have tried many strategies to combat the disease, but none have been effective enough or long-lasting.
Researchers at Boyce Thompson Institute (BTI) and in Emerging Pests and Pathogens Research Laboratory at the USDA- Agricultural Research Service in Ithaca, NY, are among many investigators working to find a solution, and their recent publication sheds light on an important strategy for controlling the spread of CLas. Published in Infection and Immunity, they present a possible mechanism for how CLas can infect its psyllid vector.
The bacteria are sucked up when a psyllid feeds on an infected tree, replicate inside the insect, and then infect healthy trees as the psyllid feeds throughout a grove. Without hitching a ride in the insect, CLas would not be able to infect new trees, and thus no new trees would succumb to citrus greening disease. With the long-term goal to disrupt this interaction, researchers in the Heck lab have focused on an important point: not all psyllids are equal in their ability to spread CLas.
"Research has shown over and over that nymphs are able to acquire the bacteria from the plant much better than adults," said Marina Mann, BTI researcher and first-author on the study. "Answering why is one of our next steps because it may give us a way to control the psyllid's ability to spread the bacteria."
To effectively be spread by psyllids, CLas must pass through the cells lining the insect's gut. The lab, under the direction of BTI professor and ARS researcher Michelle Heck, has previously shown that the gut cells of adult ACP experience a severe stress response when infected by CLas. The cell nuclei become fragmented, and some cells will even undergo apoptosis - auto-induced cell suicide. In their recent publication, the researchers report a much different response in the young psyllid nymphs.
"When we looked at nymphs, we found that their nuclei rarely reached the same level of disruption we saw in adults, and thus appeared resistant to the effects of exposure to CLas," said Mann.
The next step will be to identify the mechanism for resistance in the nymphs so that it might be reversed to halt the spread of CLas. An important clue lies in how psyllids interact with symbiotic bacteria in its gut, especially Wolbachia pipientis.
Many insects are hosts for Wolbachia, and often depend on these bacteria for important benefits - much like how human health depends on gut bacteria. In their study, Mann and Heck show that in psyllid nymphs, Wolbachia and CLas reside within the same cells. To accommodate the beneficial bacteria, the nymph gut cells may actively avoid cell suicide, which, the authors hypothesize, might help CLas get in and multiply at the same time.
Their theory is supported by their discovery that the levels of CLas in psyllid nymphs are strongly correlated with the levels of W. pipientis, meaning that the nymphs that let more Wolbachia in have also let in more CLas. Although this link remains to be tested directly, understanding its mechanism could yield an important target for disrupting the psyllid-CLas interaction.
"We now have a foothold in our understanding of a molecular difference between nymph and adult psyllids in their guts, which CLas exploits to gain entry into the insect vector," said Heck, who is lead investigator for the project. "This is important to our ability to develop new ways to block transmission by insects in the grove."
"Citrus growers will be in a much better situation in terms of disease control and saving the U.S. citrus industry," said Dan Dreyer, Chairman of the California Citrus Research Board, which funds this and other research aimed at developing a management strategy for citrus greening.
"There are still many unanswered questions about CLas, how it is acquired and transmitted via the Asian citrus psyllid and how it causes the disease," continued Dreyer. "The more we learn about CLas and its vector, the closer we will get to moving citrus production past the threat of citrus greening."
Research reported in this news release was supported by the California Citrus Research Board, grant numbers 5300-155 and 5300-163, and the USDA National Institute of Food and Agriculture, grant number 2015-70016-23028.
Alexa M. Schmitz is the Science Editorial Associate for Boyce Thompson Institute.
Communications Office 607-288-2578 Boyce Thompson Institute 533 Tower Road Ithaca, New York 14853 USA
To learn more about Boyce Thompson Institute (BTI) research, visit the BTI website.
About Boyce Thompson Institute: Boyce Thompson Institute is a premier life sciences research institution located in Ithaca, New York on the Cornell University campus. BTI scientists conduct investigations into fundamental plant and life sciences research with the goals of increasing food security, improving environmental sustainability in agriculture and making basic discoveries that will enhance human health. Throughout this work, BTI is committed to inspiring and educating students and to providing advanced training for the next generation of scientists. For more information, visit btiscience.org.
Alexa M. Schmitz | idw - Informationsdienst Wissenschaft
Dramatic transition in Streptomyces life cycle explained in new discovery
04.12.2019 | John Innes Centre
Neurodegenerative diseases may be caused by transportation failures inside neurons
04.12.2019 | Rockefeller University
With ultracold chemistry, researchers get a first look at exactly what happens during a chemical reaction
The coldest chemical reaction in the known universe took place in what appears to be a chaotic mess of lasers. The appearance deceives: Deep within that...
Abnormal scarring is a serious threat resulting in non-healing chronic wounds or fibrosis. Scars form when fibroblasts, a type of cell of connective tissue, reach wounded skin and deposit plugs of extracellular matrix. Until today, the question about the exact anatomical origin of these fibroblasts has not been answered. In order to find potential ways of influencing the scarring process, the team of Dr. Yuval Rinkevich, Group Leader for Regenerative Biology at the Institute of Lung Biology and Disease at Helmholtz Zentrum München, aimed to finally find an answer. As it was already known that all scars derive from a fibroblast lineage expressing the Engrailed-1 gene - a lineage not only present in skin, but also in fascia - the researchers intentionally tried to understand whether or not fascia might be the origin of fibroblasts.
Fibroblasts kit - ready to heal wounds
Research from a leading international expert on the health of the Great Lakes suggests that the growing intensity and scale of pollution from plastics poses serious risks to human health and will continue to have profound consequences on the ecosystem.
In an article published this month in the Journal of Waste Resources and Recycling, Gail Krantzberg, a professor in the Booth School of Engineering Practice...
Conventional light microscopes cannot distinguish structures when they are separated by a distance smaller than, roughly, the wavelength of light. Superresolution microscopy, developed since the 1980s, lifts this limitation, using fluorescent moieties. Scientists at the Max Planck Institute for Polymer Research have now discovered that graphene nano-molecules can be used to improve this microscopy technique. These graphene nano-molecules offer a number of substantial advantages over the materials previously used, making superresolution microscopy even more versatile.
Microscopy is an important investigation method, in physics, biology, medicine, and many other sciences. However, it has one disadvantage: its resolution is...
03.12.2019 | Event News
15.11.2019 | Event News
15.11.2019 | Event News
04.12.2019 | Life Sciences
04.12.2019 | Health and Medicine
04.12.2019 | Life Sciences