Comparison on the carbohydrate metabolic enzyme activities and their gene expression patterns in canola differing seed oil content

Abstract

Carbohydrates are an important regulator of canola seed oil content. However, understanding the physiological regulation by carbohydrates governing seed oil accumulation is fragmented. In the present study, activities of sucrose and starch catalytic enzymes, including neutral and alkaline invertase, sucrose synthase (SUS), and starch phosphorylase, and biosynthetic enzymes, including sucrose phosphate synthase and ADP-glucose pyrophosphorylase, were compared in developing silique and seed of high oil content and low oil content lines (HOCL and LOCL, respectively). The results showed that the HOCL had significantly higher total soluble sugar concentration in the developing silique wall and seed during the seed lipid accumulation stage. Strikingly, all the enzymes showed very strong activities at 20 days after anthesis in the silique wall of the HOCL, which was in agreement with the higher amounts of corresponding gene expression. The result indicated that the homeostasis of the high efficiency of cleavage and biosynthetic of carbohydrates in the HOCL was beneficial for the rapid volume expansion of silique and transportation of carbohydrates, i.e., sucrose and starch, to the seed for utilization. At seed deposition stage, all the enzymes exhibited significantly higher activities in the HOCL than in the LOCL, which was helpful for increased production of carbohydrates. The results of gene expression at seed oil deposition stages revealed that one of the SUS genes, SUS3, showed significantly higher transcript amount in the HOCL than in the LOCL at all stages while most of other genes showed no significant differences between two lines at developing stages. Therefore, SUS3 might be played vital roles in the sucrose cleavage.