Oil accumulation in non-seed tissue: transcriptome analysis of Chinese tallow

Abstract

Chinese tallow (Triadica sebifera) is an oil-seed producing tree with a great potential as a biofuel crop and does not compete with food crops for land. The fruits are unique in that they contain two kinds of lipid, a highly un-saturated oil and a saturated fat separated in the seed and an external tallow layer respectively. However, until recently it was unclear whether the tallow is a non-seed tissue or an external fat deposition. We have addressed this important question by scanning electron microscopy to show that it is a cellular tissue and provided biochemical evidence for an active storage oil or triacylglycerol (TAG) biosynthetic machinery in the non-seed tallow tissue. We also showed that tallow tissue accumulates more TAG and has a different fatty acid profile compared to the seed TAG. As a sequence resource to aid the development of this oil crop, we generated a transcriptome resource by sequencing three component fruit tissues of tallow, seed and fruit coat. This enabled the reconstruction of lipid biosynthesis pathway in this potential biofuel crop. The transcriptome resource has thus far allowed identification of key differences in oil synthesis and storage mechanisms between the seed and tallow tissues. This non-seed oil accumulating tissue can be used as model system to gain further knowledge of such tissues to facilitate efficient utilization of non-seed biomass for oil production.