|SHAPIRO, LORI - Harvard Medical School
|PAULSON, JOSEPH - Genentech
|ARNOLD, BRIAN - Harvard School Of Public Health
|ZHAXYBAYEVA, OLGA - Dartmouth College
|PIERCE, NAOMI - Harvard University
|KLEPAC-CERAJ, VANJA - Wellesley College
|HOLTON, KRISTINA - Dana-Farber Cancer Institute
Submitted to: mBio
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2018
Publication Date: 10/2/2018
Citation: Shapiro, L.R., Paulson, J.N., Arnold, B.J., Scully, E.D., Zhaxybayeva, O., Pierce, N., Klepac-Ceraj, V., Holton, K. 2018. An introduced crop plant is driving diversification of the virulent plant pathogen Erwinia tracheiphila. mBio. 9(5):e1307-18. https://doi.org/10.1128/mBio.01307-18.
Interpretive Summary: Erwinia tracheiphila is a recently emerged plant pathogen that causes bacterial wilt disease in cucumber, muskmelon, squash, and pumpkins in North America. Despite the fact that this pathogen causes millions of dollars in agricultural losses each year, little is known about its genetic diversity, the identity of genes linked to host range and evasion of the host plant immune system, or the number of strains currently in circulation. In this study, the genomes of 84 different isolates collected across the United States from a variety of crop species displaying symptoms of wilt were sequenced and compared. This analysis led to the identification of three genetically distinct groups, which are referred to as Et-melo, Et-1, and Et-2. While isolates from groups Et-1 and Et-2 were found predominantly in the northeastern US and were capable of infecting cucumber, muskmelon, and squash, isolates from Et-melo were found throughout the US and were able to infect cucumber and muskmelon, but not squash. Differences in the number and types of genes linked to interactions with the plant and evasion of the host plant immune system, may explain the differences in range of plants infected among these three groups. In addition, cucumber was more susceptible to E. tracheiphila overall compared to muskmelon and squash. Not only were isolates from all three groups capable of infecting this plant, but symptoms appeared more rapidly and mortality rates were higher. Taken together, these findings suggest that cucumber is one of the more susceptible crops to this pathogen and that muskmelon and squash are susceptible to some of the circulating isolates. Additionally, these findings also suggest that isolates with expanded host ranges could emerge due to the acquisition of genes from other bacteria.
Technical Abstract: Worldwide, crop plant populations are becoming more genetically homogeneous over ever larger land areas. This lack of population diversity likely increases the susceptibility of these populations to invasion followed by rapid dissemination of virulent pathogens. Erwinia tracheiphila, the etiological agent of bacterial wilt of cucurbits, is one plant pathogen that has genomic characteristics indicative of a recent emergence into a susceptible crop plant population. To investigate why this virulent pathogen infects few species of closely related cucurbit crop plants, a geographically representative collection of 84 E. tracheiphila isolates was gathered and their genomes were sequenced. Phylogenomic analysis revealed that this collection of isolates is comprised of three distinct genetic clusters. The three clusters have low within-cluster genetic variation and distinct cluster-specific effector virulence gene repertoires. In the field and in a greenhouse setting, cucumber (Cucumis sativus), which was introduced to North America by early Spanish explorers, is the most susceptible host plant species, and is the only host plant susceptible to infection by isolates from all three clusters. Now planted in high acreage in its introduced range in Eastern North America, C. sativus may be acting as a highly susceptible reservoir host for E. tracheiphila, and potentially amplifying the E. tracheiphila epidemic. These findings have broad implications for agricultural sustainability by drawing attention to how agricultural intensification and worldwide crop plant movement may affect the emergence and epidemic persistence of virulent microbial pathogens.
"Hatimaye, katika utafiti wa utafiti wa Harvard, ""Uchunguzi wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa wa Ugonjwa." Mimea ya mazao iliyoingizwa inaendesha utofauti wa vimelea vya mgonjwa wa mimea Erwinia tracheiphila. Mbio. 9 (b) (e) (e) (e) (e) (e) (e) (e) (e) (e) (e) (e) (e) (e) (e) (e) (e) (e) (e) (e) (e) (e) (e) (Kutoka kwa: www.doi.org.au) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) (M) Erwinia tracheifila ni ugonjwa wa mimea unaosababisha ugonjwa wa kuharibika kwa bakteria katika matango, muskmelon, squash, na matango huko Amerika Kaskazini. Ingawa virusi hivyo husababisha hasara ya mamilioni ya dola kwa kilimo kila mwaka, ni kidogo inayojulikana kuhusu utofauti wake wa maumbile, utambulisho wa jeni zinazohusiana na aina ya mwenyeji na kuepuka mfumo wa kinga wa mmea mwenyeji, au idadi ya aina zinazozunguka. Katika utafiti huu, genomes ya 84 tofauti isolates zilizokusanywa katika Marekani kutoka aina mbalimbali za mazao kuonyesha dalili za wilting walikuwa mfululizo na ikilinganishwa. Uchunguzi huo uliongoza kwenye utambulisho wa makundi matatu tofauti ya maumbile, yanayoitwa Et-melo, Et-1 na Et-2. Wakati isolates kutoka makundi ya Et1 na Et2 zilipatikana hasa kaskazini mashariki mwa Marekani na walikuwa na uwezo wa kuambukiza matango, muskmelon, na squash, isolates kutoka Et2 na Et2 zilipatikana kote Marekani na walikuwa na uwezo wa kuambukiza matango na muskmelon, lakini si squash. Tofauti katika idadi na aina ya jeni zinazohusiana na mwingiliano na mmea na kuepuka mfumo wa kinga wa mmea mwenyeji, inaweza kuelezea tofauti katika aina ya mimea iliyoambukizwa kati ya makundi haya matatu. Kwa kuongezea, matango yalikuwa na uwezekano mkubwa wa kuambukizwa E. tracheiphila ikilinganishwa na muskmelon na squash. Si tu kwamba vipande vya aina zote tatu vilikuwa na uwezo wa kuambukiza mmea huu, lakini dalili zilionekana haraka zaidi na viwango vya vifo vilikuwa vya juu zaidi. Kwa pamoja, matokeo haya yanaonyesha kuwa matango ni moja ya mazao ya kuathiriwa zaidi na vimelea hivi na kwamba muskmelon na squash ni kuathiriwa na baadhi ya isolates zinazozunguka. Kwa kuongezea, matokeo haya pia yanaonyesha kuwa kutengwa na safu za mwenyeji zilizopanuliwa zinaweza kutokea kwa sababu ya ununuzi wa jeni kutoka kwa bakteria zingine. Technical Abstract: Ulimwenguni pote, idadi ya mimea ya mazao inakuwa ya kawaida zaidi katika maeneo makubwa ya ardhi. Ukosefu huu wa utofauti wa idadi ya watu uwezekano huongeza unyeti wa idadi hizi kwa uvamizi ikifuatiwa na kuenea kwa haraka kwa vimelea vya magonjwa. Erwinia tracheophila, kiini cha bakteria ya kuharibika kwa cucurbits, ni moja ya vimelea vya mimea ambayo ina sifa za genomic zinazoonyesha kuibuka hivi karibuni katika idadi ya mimea ya mazao ya mimea. Ili kuchunguza kwa nini virusi hivi vinaambukiza spishi chache za mimea ya cucurbit, mkusanyiko wa kiwakilishi wa kijiografia wa 84 E. tracheophila isolates ulikusanywa na genomes zao zilipangwa. Uchambuzi wa phylogenomic ulifunua kwamba mkusanyiko huu wa isolates unajumuisha makundi matatu tofauti ya maumbile. Makundi hayo matatu yana tofauti ndogo ya maumbile ndani ya makundi na repertoires tofauti za jeni za virulence za effector maalum za makundi. Katika mazingira ya kijani kibichi, cucumber (Cucumis sativus), ambayo ilianzishwa katika Amerika ya Kaskazini na wachunguzi wa mapema wa Kihispania, ni spishi ya mmea wa mwenyeji wa kuambukizwa zaidi, na ni mmea pekee wa mwenyeji wa kuambukizwa na isolates kutoka kwa makundi yote matatu. C. sativus, ambayo sasa imepandwa katika eneo kubwa katika eneo lake la kuingizwa katika Amerika ya Kaskazini Mashariki, inaweza kuwa ikifanya kazi kama mwenyeji wa hifadhi ya E. tracheophila, na uwezekano wa kuimarisha janga la E. tracheophila. Matokeo haya yana athari kubwa kwa uendelevu wa kilimo kwa kuelekeza umakini kwa jinsi ukomavu wa kilimo na harakati za mimea ya mazao ulimwenguni inaweza kuathiri kuibuka na kudumu kwa janga la vimelea vya virusi vya bakteria.