Gene Expression and Fatty Acid Composition in Sea Buckthorn Seeds and Pulp During Fruit Development of Different Varieties

Sea buckthorn (<i>Hippophae rhamnoides</i> L.) is an oil crop with health benefits. Its fruits are rich in unsaturated fatty acids (FAs); however, the FA composition of the seeds and pulp differs significantly. To evaluate the expression levels of gene families that play a major role in FA biosynthesis, the transcriptomes of seeds and pulp at four fruit development stages were sequenced for five sea buckthorn varieties with diverse characteristics: Elizaveta, Inya, KP-686, Panteleevskaya, and Triumf. The results revealed that <i>FAD3 (07426)</i> and <i>FAD3 (05528)</i> are likely key genes for linolenic acid synthesis in seeds, while <i>FAD2 (21624)</i> is likely the main contributor to linoleic acid synthesis in both seeds and pulp. <i>SAD (18830)</i> primarily contributes to oleic acid synthesis in seeds, while <i>SAD (18830)</i> and <i>SAD (26748)</i> contribute to its synthesis in pulp. <i>FATA (14745)</i> and <i>FATA (14109)</i> are also implicated in FA synthesis in sea buckthorn fruits. Changes in the content of the main FAs in seeds and pulp correlated with the expression levels of the corresponding genes. KP-686 and Triumf differed the most from other varieties. These results are important for analyzing tissue-specific gene expression in seeds and pulp of sea buckthorn fruits, and they are promising for developing sea buckthorn varieties with improved oil composition.