“HAIRY CANOLA” – Arabidopsis GL3 Induces a Dense Covering of Trichomes on Brassica napus Seedlings

Abstract

Transformation with the Arabidopsis bHLH gene 35S:GLABRA3 (GL3) produced novel B. napus plants with an extremely dense coverage of trichomes on seedling tissues (stems and young leaves). In contrast, trichomes were strongly induced in seedling stems and moderately induced in leaves of a hairy, purple phenotype transformed with a 2.2 kb allele of the maize anthocyanin regulator LEAF COLOUR (Lc), but only weakly induced by BOOSTER (B-Peru), the maize Lc 2.4 kb allele, or the Arabidopsis trichome MYB gene GLABRA1 (GL1). B. napus plants containing only the GL3 transgene had a greater proportion of trichomes on the adaxial leaf surface, whereas all other plant types had a greater proportion on the abaxial surface. Progeny of crosses between GL3 + and GL1 + plants resulted in trichome densities intermediate between a single-insertion GL3 + plant and a double-insertion GL3 + plant. None of the transformations stimulated trichomes on Brassica cotyledons or on non-seedling tissues. A small portion of bHLH geneinduced trichomes had a swollen terminal structure. The results suggest that trichome development in B. napus may be regulated differently from Arabidopsis. They also imply that insertion of GL3 into Brassica species under a tissue-specific promoter has strong potential for developing insect-resistant crop plants.

Potential for oilseed rape resistance in pollen beetle control

“…In OSR, this biotechnology-based strategy has only been implemented (but not marketed) against flea beetles Phyllotreta spp., which are important pests in Canada feeding from cotyledons and the first true leaves. The resistance was not based on toxins but on leaf hairiness, which was increased by up to 1000 times compared to the parent line by the insertion of genes from Arabidopsis thaliana into the OSR genome (Gruber et al 2006). In field trials, this increase in trichome density led to a decrease in herbivory by flea beetles without necessarily affecting final yield (Soroka et al 2009;Alahakoon et al 2016).…”

Jasmonic acid control of GLABRA3 links inducible defense and trichome patterning inArabidopsis

“…It is known that the Myb-bHLH-WD40 complex is an evolutionarily conserved regulator of trichome development in Brassicaceae and Malvaceae, both of which belong to the Eurosid II clade of angiosperms (APG, 2003;Wang et al, 2004;Humphries et al, 2005;Gruber et al, 2006). Because GL3 is the key regulator of trichome induction in Arabidopsis, it is possible that wound-induced trichome formation in other species of Eurosid II is controlled by a similar mechanism that might have a common evolutionary origin.…”

Map-based cloning and characterization of a gene controlling hairiness and seed coat color traits in Brassica rapa

“…Consequently yellow seeds result in a better feeding value for livestock (Tang et al 1997). Hairiness in Brassica species is another important trait that is related to plant defense against insects (Agren and Schemske 1992;Gruber et al 2006).…”

“…Additionally, there are several genes, such as GLABROUS 1, 2, and 3 (GL1, GL2 and GL3) that are demonstrated to be involved in formation of trichomes (Schiefelbein 2003). Recently a hairy canola was produced using the Arabidopsis glabrous gene GL3 through genetic transformation (Gruber et al 2006). To better understand the genes controlling seed coat color and hairiness traits in Brassica crops, a Mendelian locus controlling seed coat color and trichome formation in B. rapa was targeted through map-based gene cloning.…”