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

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

'' 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 or WUSTL) is a private research university with its main campus in St. Louis County, and Clayton, Missouri. Founded in 1853, the university is named after George Washington. Washington University is r ...

, it was named after the

graduate student Postgraduate or graduate education refers to academic or professional degrees, certificates, diplomas, or other qualifications pursued by post-secondary students who have earned an undergraduate ( bachelor's) degree. The organization and stru ...

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 The Solanaceae , or nightshades, are a family of flowering plants that ranges from annual and perennial herbs to vines, lianas, epiphytes, shrubs, and trees, and includes a number of agricultural crops, medicinal plants, spices, weeds, and orna ...

plants. This strain is used for moving genes of interest into many hundreds of species of plants all over the world. For

recalcitrant Recalcitrant seeds are seeds that do not survive drying and freezing during ex-situ conservation. By and large, these seeds cannot resist the effects of drying or temperatures less than 10 °C (50 °F); thus, they cannot be stored for long periods ...

crops such as

maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. Th ...

wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...

, and

rice Rice is the seed of the grass species ''Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima ''Oryza glaberrima'', commonly known as African rice, is one of the two domesticated rice species. It was first domesticated and grown i ...

, 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 type of Horticulture, cultivated plant that people have selected for desired phenotypic trait, traits and when Plant propagation, propagated retain those traits. Methods used to propagate cultivars include: division, root and st ...

. The chromosomal background of EHA101 is C58C1, a cured

nopaline Nopaline is a chemical compound derived from the amino acids glutamic acid and arginine. It is classified as an opine. Ti plasmids are classified on the basis of the different types of opines they produce. These may be nopaline plasmids, oct ...

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. Kanamycin ...

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

antibiotic resistance Antimicrobial resistance (AMR) occurs when microbes evolve mechanisms that protect them from the effects of antimicrobials. All classes of microbes can evolve resistance. Fungi evolve antifungal resistance. Viruses evolve antiviral resistance. ...

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