Abstract
Hydroxy fatty acids (HFAs) have numerous industrial applications but are absent in most vegetable oils. Physaria lindheimeri accumulating 85% HFA in its seed oil makes it a valuable resource for engineering oilseed crops for HFA production. To discover lipid genes involved in HFA synthesis in P. lindheimeri, transcripts from developing seeds at various stages, as well as leaf and flower buds, were sequenced. Ninety-seven percent clean reads from 552,614,582 raw reads were assembled to 129,633 contigs (or transcripts) which represented 85,948 unique genes. Gene Ontology analysis indicated that 60% of the contigs matched proteins involved in biological process, cellular component or molecular function, while the remaining matched unknown proteins. We identified 42 P. lindheimeri genes involved in fatty acid and seed oil biosynthesis, and 39 of them shared 78–100% nucleotide identity with Arabidopsis orthologs. We manually annotated 16 key genes and 14 of them contained full-length protein sequences, indicating high coverage of clean reads to the assembled contigs. A detailed profiling of the 16 genes revealed various spatial and temporal expression patterns. The further comparison of their protein sequences uncovered amino acids conserved among HFA-producing species, but these varied among non-HFA-producing species. Our findings provide essential information for basic and applied research on HFA biosynthesis.
Highlights
Hydroxy fatty acids (HFAs) and their derivatives are used as raw materials for numerous industrial products, such as lubricants, plastics and surfactants [1,2]
We identified three major periods: (1) early period, up to 21 days after pollination (DAP), when developing seeds rapidly increase in size and fresh weight; (2) mid-maturation period, from 28 to 42 DAP, when lipids and dry weights accumulate steadily, but seed size and fresh weigh cease at 42 DAP and begin to decline; and (3) late-maturation/desiccation stages, from 42 DAP to 56 DAP, when seeds enter the natural dehydrate process
The de novo reconstruction of RNA-seq data resulted in a total of 129,633 contigs represented by 85,948 unique genes with an average N50 contig size (50% of all bases reside in a contig) of 1373 bp (Table 2), which is comparable to the 1310 bp of the high-quality transcriptome of P. fendleri, a relative of P. lindheimeri, which produces 20:1OH at 55–60% in seeds [58]
Summary
Hydroxy fatty acids (HFAs) and their derivatives are used as raw materials for numerous industrial products, such as lubricants, plastics and surfactants [1,2]. The conventional source of HFA is from castor (Ricinus communis), which contains 90% ricinoleic acid (12hydroxy 9-octadecenoic acid, 18:1OH) in its seed oil. Lesquerella possesses key domestication traits such as indehiscent seeds (or non-shattering seeds), photoperiod neutrality, upright growth habit, and extensive branching that leads to high seed yields, it is being developed as a safe source for HFA production [10]. Considerable breeding efforts, such as single plant or bulking recurrent selections, are made to improve lesquerella with increased HFA oil content [12]. Besides the HFAs found in plant seeds, families of saturated hydroxy fatty acids (SHFAs) have been recently discovered in cow, goat, and human milks [19,20], and the SHFAs from human milk inhibit the growth of human cancer cells and suppress beta-cell apoptosis [19], indicating that SHFAs may play a role in the promotion and protection of human health
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
