| There is a negative correlation between hypocotyl length of Brassica napus L. and its cold resistance. To study the response of BnYUCCA8 gene related to hypocotyl elongation to low temperature stress, BnYUCCA8 was cloned from B. napus by homologous cloning technique. Its CDS was composed of 1281bp nucleotides, encoding 426 amino acids. Bioinformatics analysis showed that BnYUCCA8 protein was an unstable hydrophobic protein, which was closely related to YUCCA8 protein in Brassica carinata and Brassica oleracea var. oleracea. The results of fluorescence quantitative PCR showed that expression of BnYUCCA8 was the highest in leaves and roots, and relatively low in flowers and siliques, and it was higher at seedling stage than at flowering stage. With the increase of low temperature stress, BnYUCCA8 expression decreased in general, and expression in ‘Tianyou 2288’ (weak cold resistant variety with long hypocotyl length) was higher than that in ‘16VHNTS158’ (strong cold resistant variety with short hypocotyl length). The determination results of endogenous IAA levels showed that the IAA levels in ‘16VHNTS158’ decreased by 68%， 92% and 97% respetively at 4℃， 0℃ and -4℃ for 24 h compared with room temperature (22℃), which decreased by 77%, 89% and 94% in ‘Tianyou 228’, respectively, and the IAA levels of ‘16VHNTS 158’ was 19%, 14%, 40% and 39% lower than that of ‘Tianyou 2288’ at 22℃, 4℃, 0℃ and -4℃, respectively. The correlation between BnYUCCA8 expression, endogenous IAA levels and hypocotyl length was analyzed. The results showed that the correlation coefficients between BnYUCCA8 expression and IAA levels in ‘16VHNTS158’ and ‘Tianyou 2288’ were 0.682 and 0.812 respectively, and there was a positive and positive significant correlation. The correlation coefficients between hypocotyl length and BnYUCCA8 expression were 0.54 and 0.41 respectively, and the correlation coefficients between hypocotyl length and IAA levels were 0.427 and 0.591 respectively, and there was a positive correlation. These results suggested that BnYUCCA8 might play an important role in regulating hypocotyl length and endogenous IAA levels in B. napus. |