Agricultural Research Service ( ARS ) scientist and their Oregon State University ( OSU ) partner have develop a Modern , extremely detailed genetic way to trace the spread ofAgrobacterium , one of the world ’s most important bacterial industrial plant pathogen , according to research justpublished inScience .
Agrobacteriumcauses crown - gall disease in yield tree ( apple , cherry , Charles Edward Berry , walnut ) , woody ornamentals and shrub including rose , herbaceous perennials , grapevine vine , and shade trees , in all move more than 100 nursery and greenhouse species measure at $ 16.2 billion in annual economical activity in the United States . It also is specially elusive in hydroponic harvest originate .
Agrobacterium , which causes pate - gall disease , infect woody ornamentals and bush including pink wine , among many other glasshouse crops .
What givesAgrobacteriumits virulence is the comportment of plasmids inside the bacterial cells . Plasmids are autonomously replicating DNA molecules that have become part of the bacterium but are not of the essence to the physiology of the cells . These plasmid DNA have factor that giveAgrobacteriumthe unique ability to shift a portion of the plasmid DNA into plant cubicle and genetically reprogram the host to cause disease .
These plasmids also have cistron that allowAgrobacteriumto transfer the entire plasmid horizontally from one bacterium to another rather than only vertically as in parent to offspring . Once acquiring a harmful plasmid , a previously benign variant ofAgrobacteriumcan become a novel pathogen line . This power has made control of the pathogen and tracking of an outbreak very hard .
To develop their tracking organization , the researchers first had to fancy out the factual phylogenesis and categorisation of the plasmids set up inAgrobacterium . The plasmids come in two main course of study : Tumor inducing ( Ti ) and Root inducing ( Ri ) , neither of which are immediately genetically related toAgrobacterium .
Before these studies , the accepted scientific aspect was that the frequent transfer of genetic entropy among plasmid DNA and large amount of transmissible variation amongAgrobacteriumspecies made drawing evolutionary relationships practically impossible . Without such information , it is not potential to pass over disease outbreaks .
Surprisingly , the ARS / OSU squad key Ti and Ri plasmids are all descended from just six and three lineages , respectively .
They study whole genome sequences of more than 1,500 strains from the Rhizobiales order , to whichAgrobacteriumbelongs , which showed unlike blood of Agrobacterium emerge independently and at dissimilar time in the past .
" What we found was that following the transmission of plasmid DNA themselves between bacterial cell was key to tracking disease eruption " said OSU postdoctoral scientist and computational biologist Dr. Alexandra J. Weisberg . She is co - advised by plant pathologistNiklaus Grunwaldwith the ARSHorticultural Crops Research Unitin Corvallis , Oregon and Professor Jeff Chang with OSU .
" Armed with this extensive inherited sequencing information about how to classify plasmids andAgrobacterium , we could infer both how bacteria move among nurseries and how the plasmid move among bacteria , " Weisberg said .
Having whole genome successiveness ofAgrobacteriumallowed linking nursery outbreaks on the basis of having strains with the same genome and plasmid sequences , the same genome succession but different plasmid sequences , or different genome sequences but the same plasmid sequences , Weisberg explain .
The researcher were able to track at least seven cases in which global dispersion of plant contribute to the widespread transmission of a singleAgrobacteriumstrain - plasmid compounding . In one case , they chase one glasshouse that make plants for wholesalers that may have serve as a form of patient zero source for many outbreaks . Strains of the same genotype - plasmid combination were after identified in two other nurseries in another part of the world .
With the power to separately analyze the bacteria from the plasmid DNA , they found many cases in which plasmid transmittal perpetuated disease spread . For example , the researcher found one var. / plasmid combination that was collected in 1964 . plasmid DNA with the same sequences were identified in song collected 30 - 40 years later in very unlike part of the public .
Understanding the genic basis for how pathogen likeAgrobacteriumevolve and broaden , specially in agrarian configurations , provides a new initiation for determining their spread , at high-pitched resolution , and assessing endangerment of future irruption , Weisberg explained . It leave researchers to shape whether agricultural praxis are spread bacterium / plasmid combinations or plasmids by themselves and in turning , will help growers utilize appropriate strategies to restrict spread .
" The strategy has the potential drop to be applied in tracking other diseases in plant and human / animate being epidemiology and even tracking food safety disease outbreak , " she added .
TheAgricultural Research Serviceis the U.S. Department of Agriculture ’s primary scientific in - business firm enquiry agency . Daily , ARS focuses on solutions to agricultural problems affecting America . Each dollar invested in agricultural enquiry results in $ 20 of economic impact .
Source : USDA ( Kim Kaplan )
