Joint Sino-German-Project: Functional analysis and mutagenesis of GDSL genes for breeding oilseed rape (B. napus) with higher oil content GDSL

油菜籽是中德两国重要的大田作物，也是植物食用油的主要来源。首届中德油菜籽遗传与生物技术研讨会于2013年4月3日至6日在杭州举行。在研讨会上，浙江大学姜丽西教授与德国基尔大学Christian- albrecht -University Kiel教授Christian Jung及其同事讨论了系统克隆和分析拟南芥种子脂肪酸还原酶（SFAR）基因以及鉴定甘油甘蓝BnSFAR基因敲除突变体的合作。为了提高种子含油量，人们在提高油脂生物合成效率方面做了很多努力，但在油脂积累过程中对油脂分解的阻断却很少关注。SFARs被定义为在种子中表达的gdsl型脂肪酶基因。它们能水解甘油三酯，减少种子脂质的积累。江教授小组的初步研究指出，拟南芥中约有25个sfar。5个基因（SFAR1 - SFAR5）的断裂导致种子中脂肪酸（FA）显著增加。此外，多个sfar位点的功能丧失对促进种子产油具有加性效应。由于拟南芥和油菜同属芸苔科植物，因此它们可能具有相同的调控机制来控制代谢途径。因此，我们推断，BnSFAR突变体的破坏增加了甘蓝型油菜的种子油产量，而BnSFAR突变体的金字塔化可能导致更高的种子油含量。中国农业大学Jungs教授小组建立了一个油菜突变群体，可以很容易地通过TILLING（靶向诱导局部基因组病变）方案筛选。该合作项目旨在(1)系统克隆拟南芥SFAR基因，了解其功能和调控机制；(2)鉴定油菜SFAR基因5个同源基因（AtSFAR1 - AtSFAR5），筛选敲低突变体；(3)研究Bnsfar突变对油菜种子含油量和Bnsfar基因突变体的影响。

Rapeseed is an important field crop and the major source of plant edible oil in both China and Germany. The first Sino-German Workshop on Genetics and Biotechnology of Rapeseed took place in Hangzhou on April 3-6, 2013. During the workshop Prof. Lixi Jiang of Zhejiang University (ZJU), Prof. Christian Jung of Christian-Albrechts-University Kiel (CAU) and their coworkers discussed the cooperation to systemically clone and analyze Seed Fatty Acid Reducer (SFAR) genes in Arabidopsis and identify BnSFAR knock-out mutants in Brassica napus. To increase seed oil content, many efforts have been made on the promotion of lipid biosynthesis efficiency, but little attention has been paid on the blocking of lipid decomposition in the process of oil accumulation. SFARs are defined as GDSL-type lipase genes that are expressed in seeds. They hydrolyze triacylglycerol and reduce the accumulation of seed lipids. Preliminary studies from Prof. Jiangs group pointed at ca. 25 SFARs in Arabidopsis. The disruption of 5 genes (SFAR1 - SFAR5) resulted in significant increases of fatty acids (FA) in seeds. Moreover, the loss of function at multiple sfar loci had an additive effect on promoting seed oil production. Since Arabidopsis thaliana and oilseed rape (Brassica napus) belong to the Brassicaceae family, it is expected that they share the same regulatory mechanisms to control metabolic pathways. Therefore we reason that disruption of a BnSFAR increases seed oil production in B. napus, and pyramiding Bnsfar mutants could lead to an even higher seed oil content. Prof. Jungs group at CAU has established a rapeseed mutant population which can be easily screened by a TILLING (targeting induced local lesions in genomes) protocol. The proposed joint project aims to (1) systematically clone putative Arabidopsis SFARs and to understand their functions and regulation, (2) to identify the orthologs of 5 SFAR genes (AtSFAR1 - AtSFAR5) in B. napus and to select knock down mutants, and (3) to characterize the effect of Bnsfar mutations on seed oil content and pyramide bnsfar mutations in oilseed rape (B. napus).