Improving seed germination and oil contents by regulating the GDSL transcriptional level in Brassica napus.

Abstract

Seed germination rate and oil content can be regulated at theGDSL transcriptional level by eitherAtGDSL1 orBnGDSL1 inB. napus. Gly-Asp-Ser-Leu (GDSL)-motif lipases represent an important subfamily of lipolytic enzymes, which play important roles in lipid metabolism, seed development, abiotic stress, and pathogen defense. In the present study, two closely related GDSL-motif lipases, Brassica napus GDSL1 and Arabidopsis thaliana GDSL1, were characterized as functioning in regulating germination rate and seed oil content in B. napus. AtGDSL1 and BnGDSL1 overexpression lines showed an increased seed germination rate and improved seedling establishment compared with wild type. Meanwhile, the constitutive overexpression of AtGDSL1 and BnGDSL1 promoted lipid catabolism and decreased the seed oil content. While RNAi-mediated suppression of BnGDSL1 (Bngdsl1) in B. napus improved the seed oil content and decreased seed germination rate. Moreover, the Bngdsl1 transgenic seeds showed changes in the fatty acid (FA) composition, featuring an increase in C18:1 and a decrease in C18:2 and C18:3. The transcriptional levels of six related core enzymes involved in FA mobilization were all elevated in the AtGDSL1 and BnGDSL1 overexpression lines, but strongly suppressed in the Bngdsl1 transgenic line. These results suggest that improving the seed germination and seed oil content in B. napus could be achieved by regulating the GDSL transcriptional level.