Genetic Engineering of Maize (Zea mays) for High-Level Tolerance to Treatment with the Herbicide Dicamba

Abstract

Herbicide-tolerant crops have been widely and rapidly adopted by farmers in several countries due to enhanced weed control, lower labor and production costs, increased environmental benefits, and gains in profitability. Soon to be introduced transgenic soybean and cotton varieties tolerant to treatments with the herbicide dicamba offer prospects for excellent broadleaf weed control in these broadleaf crops. Because monocots such as maize (Zea mays) can be treated with dicamba only during a limited window of crop development and because crop injury is sometimes observed when conditions are unfavorable, transgenic maize plants have been produced and tested for higher levels of tolerance to treatment with dicamba. Maize plants expressing the gene encoding dicamba monooxygenase (DMO) linked with an upstream chloroplast transit peptide (CTP) display greatly enhanced tolerance to dicamba applied either pre-emergence or postemergence. Comparisons of DMO coupled to CTPs derived from the Rubisco small subunit from either Arabidopsis thaliana or Z. mays showed that both allowed production of transgenic maize plants tolerant to treatment with levels of dicamba (i.e., 27 kg/ha) greatly exceeding the highest recommended rate of 0.56 kg/ha.

Citrus Transformation: Challenges and Prospects

“…According to the USDA economic research service, genetically engineered (GE) crops have been widely adopted since their introduction in 1996 (USDA, 2010). Herbicidetolerant genetically engineered soybeans and cotton have been the most extensively and rapidly adopted GE crops in the U.S., followed by insect-resistant cotton and corn (Cao et al, 2010). The positive impact of these GE crops was due to lower labor and production costs, and gains in profitability, in addition to their increased environmental benefits.…”

Spectrum of Weed Control With 2,4-D and Dicamba Herbicides Associated to Glyphosate or Not

“…For these species, the addition of an auxin mimic like 2,4-D to glyphosate accelerates and improves control levels (Takano et al, 2013). Even with the use of dicamba in maize and wheat cultures during previous decades (Behrens et al, 2007;Cao et al, 2011), there is little information related to the herbicide effectiveness on these weed species. Currently, no dicamba-based commercial product is registered to be used in Brazil.…”

A small-scale, inexpensive method for detecting formaldehyde or methanol in biochemical reactions containing interfering substances

“…1A). The ability of DMO to inactivate dicamba has been used to create dicamba-resistant transgenic crop plants [7,8] that soon will be commercially available to farmers.…”

“…1A). The ability of DMO to inactivate dicamba has been used to create dicamba-resistant transgenic crop plants [7,8] that soon will be commercially available to farmers.The recent determination of the crystal structure of DMO [9] has provided strong suggestive evidence that molecular oxygen, activated by transfer of electrons from the enzyme's free iron atom, contributes one of its oxygen atoms to disruption of a C-H bond in the O-methyl group of dicamba. Earlier publications from our laboratory [4,5] favored a postulated, but yet to be detected, hemiacetal intermediate that was proposed to spontaneously decompose to release formaldehyde and DCSA (Fig.…”

“…Simpler, inexpensive methods for detecting formaldehyde, such as the use of the Purpald reagent [1], often are adequate, but can suffer from the presence of interfering substances in reaction mixtures. Such has been the case in our studies with dicamba (2-methoxy-3,6-dichlorobenzoic acid) monooxygenase (DMO) [2][3][4][5][6][7][8], in which we wished to establish with certainty that formaldehyde was an end product of the enzyme-catalyzed O-demethylation of dicamba. To eliminate the problem of interfering substances in our DMO reaction mixtures, we developed a simple microdistillation technique that yielded sufficiently pure formaldehyde to allow uncompromised use of Purpald for detection purposes.…”