Exogenous gibberellin affects reserve accumulation during seeds filling in Brassica Napus
Xingqun Huang¹, Xiaoying Zhao¹, Reqing He¹, Bo Zhou¹, Wusheng Peng³, Yuhong Zhuo³, Jianzhong Lin¹, Dongying Tang¹, Jihong Zhang¹, Xuanming Liu*^1,2 

¹Bioenergy and Biomaterial Research Center, College of Biology, Hunan University, Changsha 410082.
²State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082.
³Academy of Seed Industry of Hunan Yahua, Changsha 410001.
*Corresponding author: Tel: (+86731)88821721;Fax:(+86731)88821721; E-mail: xml05@hnu.edu.cn

Abstract
Exogenous Gibberellins (GAs) are applied in agriculture broadly and their physiological functions and biochemistry mechanism become more and more clear, but little is known about the effect of GAs on the reserve substance accumulation during seed maturing. In this paper, it is shown that GAs acts as a physiological regulator in the regulation of carbohydrate, protein, and lipids accumulation in developing seeds of Brassica Napus. It was found that the oil and total sugar content of seeds increased by 4.70% and 6.77%, and the crude protein content decreased by 3.18% in the samples treated with GA₃ at 15 DAF (days after flower); the total sugar content increased by 4.10%, and the crude protein content decreased by 5.77% treated with GA₃ at 25 DAF; the crude protein and total sugar content increased by 5.85% and 5.04% treated with GA₃ at 35DAF. Q-PCR analysis results showed the transcription levels of three transcription factors (LEC1, LEC2 and WRI), sucrose transporter SUC2, and key oil-synthesis gene DGAT were upregulated in response to GA at 15DAF, and the transcription factor ABI3, ABI5, and storage protein gene Napin were downregulated in GA-treated samples at 25DAF, while upregulated at 35DAF, which consistent with the reserve accumulation results. These results indicated that the effect of GAs on the reserve accumulation may be due to the altered lipid, protein, sugar metabolism related gene expression.

Key Words: Gibberellins; reserve accumulation; gene expression; Seed Maturing; Brassica napuss