Hypocotyl elongation based on HY5 transcription factor in cold resistant winter rapeseed (Brassica napus L.)

Winter rape (Brassica napus L.) is better than other edible oil crops in China, but poor cold resistance is the key factor restricting its development. Hypocotyl length was found closely related to cold tolerance. ​The correlation between hypocotyl length and semi-lethal low temperature was significant, and the highest correlation between hypocotyl length and LT50 of autumn sowing was 0.9557. When the hypocotyl were treated at low temperature, the cells were seriously damaged and formed cavity structures, with cell walls seriously damaged or merged into each other. The positive regulation gene of hypocotyl length in resistant line of VHTSG 10 was identified as HY5 (transcription factor HY5-like) by qPCR, and bZIP transcription factor was found to be its conserved domain. Fused gene by GFP and HY5 from VHTSG 10 was transient transferred into Nicotiana benthamiana cells. Corresponding to the 35S:GFP widely distributed in plasma membrane of leaf epidermis, the fusion protein 35S:HY5-GFP was mainly distributed in nucleus. Thus we regarded BnHY5 gene is a key gene related to cold tolerance and hypocotyl length in B. napus.