The biosynthesis of benzoxazinone, a cyclic hydroxamate and a natural

insecticide Insecticides are substances used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed to b ...

, has been well-characterized in maize and related grass species. In maize, genes in the pathway are named using the symbol ''bx''. Maize Bx-genes are tightly linked, a feature that has been considered uncommon for plant genes of a biosynthetic pathways. Especially notable are genes encoding the different enzymatic functions BX1, BX2 and BX8 and which are found within about 50 kilobases. Results from wheat and

rye Rye (''Secale cereale'') is a grass grown extensively as a grain, a cover crop and a forage crop. It is a member of the wheat tribe (Triticeae) and is closely related to both wheat (''Triticum'') and barley (genus ''Hordeum''). Rye grain is u ...

indicate that the cluster is an ancient feature. In wheat the cluster is split into two parts. The wheat genes Bx1 and Bx2 are located in close proximity on chromosome 4 and wheat Bx3, Bx4 and Bx5 map to the short arm of chromosome 5; an additional Bx3 copy was detected on the long arm of chromosome 5B. Recently, additional biosynthetic clusters have been detected in other plants for other biosynthetic pathways and this organization might be common in plants.

Maize genes

The

bx1 The Bx1 and Bx2 are two bus routes that run on the Grand Concourse in the Bronx, New York City. The routes, which are operated by the MTA Regional Bus Operations, also follow Sedgwick Avenue and Mosholu Parkway for a short distance at their no ...

gene encodes a protein, BX1, that forms indol from indol-3-glycerol phosphate in the

plastid The plastid (Greek: πλαστός; plastós: formed, molded – plural plastids) is a membrane-bound organelle found in the Cell (biology), cells of plants, algae, and some other eukaryotic organisms. They are considered to be intracellular endosy ...

. It is the first step in the pathway and determines much of the natural variation in levels of

DIMBOA DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one) is a naturally occurring hydroxamic acid, a benzoxazinoid. DIMBOA is a powerful antibiotic present in maize, wheat, rye, and related grasses, DIMBOA was first identified in maize in 1962 as ...

in maize. The next steps in the pathway occur in the

endoplasmic reticulum The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ( ...

, also referred to as the

microsomes In cell biology, microsomes are heterogeneous vesicle-like artifacts (~20-200 nm diameter) re-formed from pieces of the endoplasmic reticulum (ER) when eukaryotic cells are broken-up in the laboratory; microsomes are not present in healthy, livin ...

in cell fractionation experiments, and are carried by proteins encoded by genes bx2, bx3, bx4, and bx5.

References

{{reflist Biochemistry Genetics Biosynthesis