EHA101 was one of the first and most widely used ''

Agrobacterium ''Agrobacterium'' is a genus of Gram-negative bacteria established by Harold J. Conn, H. J. Conn that uses horizontal gene transfer to cause tumors in plants. ''Agrobacterium tumefaciens'' is the most commonly studied species in this genus. ''Agr ...

'' helper plasmid for plant gene transfer. Created in 1985 in the laboratory of Mary-Dell Chilton at

Washington University in St. Louis Washington University in St. Louis (WashU) is a private research university in St. Louis, Missouri, United States. Founded in 1853 by a group of civic leaders and named for George Washington, the university spans 355 acres across its Danforth ...

, it was named after the

graduate student Postgraduate education, graduate education, or graduate school consists of Academic degree, academic or professional degrees, certificates, diplomas, or other qualifications usually pursued by higher education, post-secondary students who have ...

who constructed it. The EH stands for "Elizabeth Hood" and A for "''Agrobacterium''". The EHA101 helper strain is a derivative of A281, the hypervirulent ''A. tumefaciens'' strain that causes large, fast-growing tumors on solanaceous plants. This strain is used for moving genes of interest into many hundreds of species of plants all over the world. For recalcitrant crops such as

maize Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native American ...

wheat Wheat is a group of wild and crop domestication, domesticated Poaceae, grasses of the genus ''Triticum'' (). They are Agriculture, cultivated for their cereal grains, which are staple foods around the world. Well-known Taxonomy of wheat, whe ...

, and

rice Rice is a cereal grain and in its Domestication, domesticated form is the staple food of over half of the world's population, particularly in Asia and Africa. Rice is the seed of the grass species ''Oryza sativa'' (Asian rice)—or, much l ...

, the EHA helper strains are often employed for gene transfer. These strains are efficient at promoting T-DNA transfer because of the hypervirulence of the vir genes suggesting that a higher success rate can be achieved on these "hard to transform" crops or

cultivars A cultivar is a kind of cultivated plant that people have selected for desired traits and which retains those traits when propagated. Methods used to propagate cultivars include division, root and stem cuttings, offsets, grafting, tissue cult ...

. The chromosomal background of EHA101 is C58C1, a cured nopaline strain. The helper strains were derived from A281, which is A136(pTiBo542). A281 was genetically engineered through a double crossover, site-directed deletion to yield EHA101, a T-DNA deleted strain useful for target gene transfer into plants. EHA101 is resistant to

kanamycin Kanamycin A, often referred to simply as kanamycin, is an antibiotic used to treat severe bacterial infections and tuberculosis. It is not a first line treatment. It is used by mouth, injection into a vein, or injection into a muscle. Kanamy ...

by way of an npt I gene in place of T-DNA. The parent strain, A281, does not show

antibiotic resistance Antimicrobial resistance (AMR or AR) occurs when microbes evolve mechanisms that protect them from antimicrobials, which are drugs used to treat infections. This resistance affects all classes of microbes, including bacteria (antibiotic resis ...

s at higher levels than normal ''A. tumefaciens'' strains. Moreover, other transconjugant strains in the C58C1 background, do not show these increased resistances to antibiotics. Therefore, these characteristics are not simply a manifestation of the chromosomal background, but most likely an interaction of this Ti plasmid and the C58 chromosomal background. The npt I gene in place of the T-DNA in EHA101 requires that binary plasmids that are put into the strain encode a drug resistance other than kanamycin. Strains EHA105 was generated from EHA101 through site-directed deletion of the kanamycin resistance gene from the Ti plasmid, otherwise the strains are identical. This latter strain has been useful to plant biotechnologists who use kanamycin as a selectable marker on their binary plasmids.

References

Plasmids Molecular biology techniques {{genetics-stub