g11 Brome grass

g11 Brome grass Scientific Information

Type:

Whole Allergen

Display Name:

Brome grass

Allergen code:

g11

Family:

Poaceae (Gramineae)

Species:

Bromus inermis

Route of Exposure:

Inhalation of pollen

Latin Name:

Bromus inermis

Other Names:

Smooth brome, Hungarian brome, Russian brome, Awnless brome (1, 2)

Summary

Bromus inermis is a perennial cool-season grass species that produces pollen that is considered to contribute to hay fever symptoms in central and western North America. However, no further details are available as case reports specifically associating B. inermis pollen with allergic symptoms have not been published to date. Three allergenic molecules have been characterized from brome grass pollen, including a Group 1 expansin (Bro i 1), a Group 5 ribonuclease (Bro i 5), and a calcium-binding protein (Bro i 7). Pooideae grasses have marked homology of major allergen groups 1, 2/3, 4, and 5, and a degree of cross-reactivity between B. inermis and other Pooideae species can be expected.

Allergen

Nature

Bromus inermis is a perennial cool-season grass species which grows 0.4‒1.0 m tall and has an extensive root system that can extend 1.5 m (5 feet) underground (2, 4). Two general types can be distinguished: the ‘southern’ type has earlier spring growth and is strongly rhizomatous with leaves near the base of the stem and long glumes, while the ‘northern’ type is weakly rhizomatous with leaves well up on the stem and short glumes (2). The inflorescence is an open panicle 6‒17 cm in length, bearing 6 to 11 lance-shaped flowered spikelets which are 1.5‒3 cm long with no awn (2, 4). Flat, dark green leaves are 10‒40 cm in length with a distinctive w-shaped constriction mid-leaf (2, 4)

Smooth brome is a long-lived species due to cloning, with some plantings known to have persisted for at least 60 years (2). B. inermis is usually cross-pollinated but can self-fertilize from different spikelets on the same plant, and reproduces via seed, rhizomes, and tillers (2). Flowering depends on region and elevation, generally May–July in North America, and June–September in Europe (2, 4). Pollen from brome grasses including B. inermis and native California brome (B. carinatus) are considered significant inducers of hay fever in California, the Pacific Northwest, and the Midwest regions of North America (4).

Taxonomy

Taxonomic tree of Bromus inermis (Brome grass) (1)
Domain	Eukaryota
Kingdom	Plantae
Phylum	Spermatophyta
Subphylum	Angiospermae
Class	Monocotyledonae
Family	Poaceae
Genus	Bromus

Environmental Characteristics

Living environment

B. inermis is highly adaptable, resistant to cold and drought, and dominates many native grassland and field habitats, riparian zones, valley bottoms, and dryland sites with moderate shade or full sun up to an elevation of 3,300 m (2). Smooth brome grows best on moist, well drained soils in regions with more than 380 mm annual precipitation, but can also tolerate acid and/or slightly saline soils (2).

B. inermis has been widely and deliberately planted due to its high palatability to livestock, tolerance to grazing, and successful use in rehabilitation or remediation of disturbed or polluted habitats (2). Smooth brome persists in habitats where it is planted, such as mountain ranges, old saltgrass meadows, or grasslands which have been overgrazed, eroded or burned [FEIS, WEB09]. Cultivars can survive fire by sprouting from rhizomes (2). B. inermis is recommended for erosion control and waterway stabilization throughout North America, as rhizomatous cultivars are a good soil binder (2). Additionally, B. inermis can be used to strip significant quantities of pollutants such as high molecular weight polycyclic aromatic hydrocarbons or heavy metal mining deposits from soil (2, 5).

Worldwide distribution

Smooth brome is native to Eurasia, and can also be found throughout North America, Africa, and Australia (1, 2). Peak airborne levels of brome grass pollen have been recorded in early June in Germany (6), from late May to mid-July in Canada (7), from June to October in the Czech Republic (8), and from October to December in the Western Cape (South Africa) (9).

Route of Exposure

Main

Inhalation of pollen produced by B. inermis can elicit allergic symptoms in sensitized individuals (4).

Clinical Relevance

Pollen from brome grasses including B. inermis is considered to contribute to hay fever symptoms in central and western North America (4), however, no further details are available as case reports specifically associating B. inermis pollen with allergic symptoms have not been published to date.

Molecular Aspects

Allergenic molecules

The following allergens have been characterized from B. inermis pollen (10):

Name	Source	Biological Function	Molecular Weight
	Bromus inermis, Grasses, Plants, Poaceae, Smooth Brome Grass
Bro I 1		a CCD-bearing protein (XF), a Group 1 expansin	-
Bro I 5		a Group 5 protein, a ribonuclease	-
Bro I 7		a calcium-binding protein (CBP), pocalcin	-

Cross-reactivity

An early study demonstrated significant cross-allergenicity and similar radioallergosorbent test (RAST) inhibition patterns between northern grasses (Timothy grass, June grass, rye grass, red top, and meadow fescue) and brome grass, western wheat, and quack grasses (11). However, another study found no antigenic cross-reactivity between pollen from Bermuda grass (Cynodon dactylon), which is classed as a southern grass, and B. inermis (12).

Pooideae grasses have marked homology of major allergen groups 1, 2/3, 4, and 5, and smooth brome is a member of the Poeae tribe which also includes Kentucky bluegrass, fescue, and orchard grasses (4). As such, and despite a lack of published studies specifically assessing cross-reactivity of the three B. inermis allergens, a degree of cross-reactivity between B. inermis and other Pooideae species can be expected.

Compiled By

Author: RubyDuke Communications

Reviewer: Dr. Christian Fischer

Last reviewed:April 2022

References

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Schumacher MJ, Griffith RD, O'Rourke MK. Recognition of pollen and other particulate aeroantigens by immunoblot microscopy. Journal of Allergy and Clinical Immunology. 1988;82(4):608-16.