Engineering Improved Seed Degreening in Brassica napus (canola)

Frost during Brassica napus (canola) embryo development increases seed chlorophyll content at maturity causing losses to canola producers. In Arabidopsis, it was demonstrated that the transcription factor, ABI3, regulates genes responsible for seed maturation and de-greening. During seed maturation, ABI3 is required for the activation of the SGR2 (stay-green) which drives degreening and overexpression of ABI3 was sufficient to impart frost-tolerant degreening. Given the high sequence similarity between Arabidopsis and canola, this system can be easily translated into canola. ABI3 homolog isolated from canola was able to complement Arabidopsis abi3-6 mutant, indicating conserved function. Canola transgenics overexpressing ABI3 were developed and were shown to promote significant degreening of seeds despite frost exposure. These transgenic lines also did not exhibit any deleterious pleiotropic effects. This study provides evidence for how enhanced expression of ABI3 confers frost-tolerant degreening, a trait that could be easily incorporated into canola hybrids.