Exogenous gibberellin weakens lipid breakdown by increasing soluble sugars levels in early germination of zanthoxylum seeds.

Zanthoxylum is a precious medicinal woody plant with a very low seed germination rate in China. The gibberellin (GA) treatment extremely increased the germination rate of zanthoxylum seeds. Our previous transcriptome data showed that exogenous GA played a negative role in the expression levels of genes involved in lipid metabolism during imbibition. Our present data indicated that compared with the GA-treated seeds, the soluble sugars were more quickly consumed and lipid breakdown was prematurely and actively initiated in the water-treated seeds during the early germination. However, the application of sucrose could improve the germination of water-treated seeds and significantly inhibit lipid breakdown. Both the application of sucrose and exogenous GA could significantly reduce the catalytic activities of sugar-dependent 1 (SDP1) and isocitratelyase (ICL), the expressions of SDP1 and ICL genes, and decrease the products of lipid breakdown as well during the early germination. We suggested that exogenous GA might enhance starch hydrolysis by promoting the catalytic activity of ɑ-amylase to supplement metabolically consumed soluble sugars, thus the increased sugars levels would help to inhibit the lipid breakdown to mitigate oxidative damages in the early germination of zanthoxylum seeds. In the end, we summarized the possible molecular mechanism on the exogenous GA weakening lipid breakdown by increasing soluble sugars levels in the early germination of zanthoxylum seeds.