Chlorophyll and carbohydrate metabolism in developing silique and seed are prerequisite to seed oil content of Brassica napus L.

Abstract

BackgroundAlthough the seed oil content in canola is a crucial quality determining trait, the regulatory mechanisms of its formation are not fully discovered. This study compared the silique and seed physiological characteristics including fresh and dry weight, seed oil content, chlorophyll content, and carbohydrate content in a high oil content line (HOCL) and a low oil content line (LOCL) of canola derived from a recombinant inbred line in 2010, 2011, and 2012. The aim of the investigation is to uncover the physiological regulation of silique and seed developmental events on seed oil content in canola.ResultsOn average, 83% and 86% of silique matter while 69% and 63% of seed matter was produced before 30 days after anthesis (DAA) in HOCL and LOCL, respectively, over three years. Furthermore, HOCL exhibited significantly higher fresh and dry matter at most developmental stages of siliques and seeds. From 20 DAA, lipids were deposited in the seed of HOCL significantly faster than that of LOCL, which was validated by transmission electron microscopy, showing that HOCL accumulates considerable more oil bodies in the seed cells. Markedly higher silique chlorophyll content was observed in HOCL consistently over the three consecutive years, implying a higher potential of photosynthetic capacity in siliques of HOCL. As a consequence, HOCL exhibited significantly higher content of fructose, glucose, sucrose, and starch mainly at 20 to 45 DAA, a key stage of seed lipid deposition. Moreover, seed sugar content was usually higher than silique indicating the importance of sugar transportation from siliques to seeds as substrate for lipid biosynthesis. The much lower silique cellulose content in HOCL was beneficial for lipid synthesis rather than consuming excessive carbohydrate for cell wall.ConclusionsSuperior physiological characteristics of siliques in HOCL showed advantage to produce more photosynthetic assimilates, which were highly correlated to seed oil contents.Electronic supplementary materialThe online version of this article (doi:10.1186/1999-3110-55-34) contains supplementary material, which is available to authorized users.

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

“…Considerable total soluble sugar deposition was observed in the early developing silique wall and seed (mainly liquid endosperm) supported the viewpoint these compounds played key roles in maintaining cellular turgidity for their rapid volume expansion (da Silva et al 1997). Another piece of evidence for this inference was the small quantity of lipids accumulated (\350 mg g -1 ) in canola seed though the seed oil content was markedly different at the early stage (Hua et al 2014).…”

“…Because silique is the essential photosynthetic organ (Gammelvind et al 1996), rapid catalysis of the photoassimilates is required because release of the small molecular sugar is very important for its volume expansion and transportation into the developing seed. Previous studies reported that rapid growth of silique occurred from initial flowering to 40 DAA (Hua et al 2014). Thus, more carbohydrates accumulation is an essential issue for silique growth, and coordination of the breakdown of sucrose and starch by related enzymes is required to supply enough substrate.…”

“…Previous investigations documented that carbohydrate profile, which includes fructose, glucose, sucrose, starch, and cellulose contents, differed significantly between HOCL and LOCL both in developing silique wall and seed in canola (Hua et al 2014). To further elucidate the physiological mechanism underlying the effect of carbohydrate metabolism on the seed oil content in the HOCL and LOCL, a systematic comparison of carbohydrate metabolism-related enzymes, including invertase, SUS, SPS, SS, and AGPase activities and their corresponding genes, was performed using the two lines during seed development.…”

“…The sampling stages were based on the previous study, which were key stages for seed lipid deposition (Hua et al 2014). The samples were ground into powder with liquid nitrogen.…”

“…The results revealed that the HOCL had significant advantages in the production of more carbohydrates over the LOCL. The correlation between carbohydrate and seed oil content uncovered the importance of soluble hexose and seed starch in oil content (Hua et al 2014). However, the differences of activities of enzymes, such as invertase and SUS, during seed development in different canola seed oil content lines remain unknown.…”