Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore, 117604, Republic of Singapore.
Biotechnol Biofuels. 2012 Jul 18;5(1):47. doi: 10.1186/1754-6834-5-47.
Temporal and spatial expression of fatty acid and lipid biosynthetic genes are associated with the accumulation of storage lipids in the seeds of oil plants. In jatropha (Jatropha curcas L.), a potential biofuel plant, the storage lipids are mainly synthesized and accumulated in the endosperm of seeds. Although the fatty acid and lipid biosynthetic genes in jatropha have been identified, the expression of these genes at different developing stages of endosperm has not been systemically investigated.
Transmission electron microscopy study revealed that the oil body formation in developing endosperm of jatropha seeds initially appeared at 28 days after fertilization (DAF), was actively developed at 42 DAF and reached to the maximum number and size at 56 DAF. Sixty-eight genes that encode enzymes, proteins or their subunits involved in fatty acid and lipid biosynthesis were identified from a normalized cDNA library of jatropha developing endosperm. Gene expression with quantitative reverse-transcription polymerase chain reaction analysis demonstrated that the 68 genes could be collectively grouped into five categories based on the patterns of relative expression of the genes during endosperm development. Category I has 47 genes and they displayed a bell-shaped expression pattern with the peak expression at 28 or 42 DAF, but low expression at 14 and 56 DAF. Category II contains 8 genes and expression of the 8 genes was constantly increased from 14 to 56 DAF. Category III comprises of 2 genes and both genes were constitutively expressed throughout endosperm development. Category IV has 9 genes and they showed a high expression at 14 and 28 DAF, but a decreased expression from 42 to 56 DAF. Category V consists of 2 genes and both genes showed a medium expression at 14 DAF, the lowest expression at 28 or 42 DAF, and the highest expression at 56 DAF. In addition, genes encoding enzymes or proteins with similar function were differentially expressed during endosperm development.
The formation of oil bodies in jatropha endosperm is developmentally regulated. The expression of the majority of fatty acid and lipid biosynthetic genes is highly consistent with the development of oil bodies and endosperm in jatropha seeds, while the genes encoding enzymes with similar function may be differentially expressed during endosperm development. These results not only provide the initial information on spatial and temporal expression of fatty acid and lipid biosynthetic genes in jatropha developing endosperm, but are also valuable to identify the rate-limiting genes for storage lipid biosynthesis and accumulation during seed development.
脂肪酸和脂质生物合成基因的时空表达与油料作物种子中储存脂质的积累有关。在麻疯树（Jatropha curcas L.）中，一种潜在的生物燃料植物，储存脂质主要在种子的胚乳中合成和积累。尽管已经鉴定出麻疯树中的脂肪酸和脂质生物合成基因，但这些基因在胚乳不同发育阶段的表达尚未系统研究。
透射电子显微镜研究表明，麻疯树种子发育胚乳中的油体形成最初出现在受精后 28 天（DAF），在 42 DAF 时活跃发育，并在 56 DAF 时达到最大数量和大小。从麻疯树发育胚乳的标准化 cDNA 文库中鉴定出 68 个编码参与脂肪酸和脂质生物合成的酶、蛋白质或其亚基的基因。定量逆转录聚合酶链反应分析表明，根据基因在胚乳发育过程中的相对表达模式，68 个基因可分为五类。第 I 类有 47 个基因，它们表现出钟形表达模式，在 28 或 42 DAF 时达到峰值，但在 14 和 56 DAF 时表达水平较低。第 II 类包含 8 个基因，这些基因的表达从 14 天到 56 天持续增加。第 III 类由 2 个基因组成，这 2 个基因在整个胚乳发育过程中均有表达。第 IV 类有 9 个基因，它们在 14 和 28 DAF 时表达水平较高，但从 42 到 56 DAF 时表达水平降低。第 V 类由 2 个基因组成，这 2 个基因在 14 DAF 时表达水平中等，在 28 或 42 DAF 时表达水平最低，在 56 DAF 时表达水平最高。此外，在胚乳发育过程中，具有相似功能的酶或蛋白质编码基因的表达存在差异。
麻疯树胚乳中油体的形成受发育调控。大多数脂肪酸和脂质生物合成基因的表达与麻疯树种子中油体和胚乳的发育高度一致，而具有相似功能的酶编码基因的表达可能在胚乳发育过程中存在差异。这些结果不仅为麻疯树发育胚乳中脂肪酸和脂质生物合成基因的时空表达提供了初步信息，而且对于鉴定种子发育过程中储存脂质生物合成和积累的限速基因也具有重要价值。
