Seed development and hydroxy fatty acid biosynthesis in physaria lindheimeri

Authors: Chen, Grace; Riiff, Timothy; Johnson, Kumiko; Boettcher, Eva; KIM, HYUN - Sejong University; LEE, KYEONG-RYEOL - Sejong University; Lin, Jiann

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2017
Publication Date: 7/10/2017
Citation: Chen, G.Q., Riiff, T.J., Johnson, K., Morales, J.S., Kim, H.U., Lee, K., Lin, J.T. 2017. Seed development and hydroxy fatty acid biosynthesis in physaria lindheimeri. Industrial Crops and Products. 108(108):410-415.

Interpretive Summary: Castor seed oil is a commercial source of hydroxy fatty acid (HFA) with numerous industrial applications. However, castor seeds contain lethal toxin and potent allergens. A safe source of HFA is from lesquerella (Physaria fendleri) seed oil, which contains a major HFA, lesquerolic acid (20:1OH), at 55–60%. Compared with castor oil which contains 90% HFA, ricinoleic acid (18:1OH), lesquerella remains to be improved for its HFA level to be cost-competitive. A related species, Physaria lindheimeri (formerly Lesquerella lindheimeri), accumulates up to 85% 20:1OH in its seed which makes P. lindheimeri a valuable genetic resource. Genes and regulatory elements from P. lindheimeri are excellent targets for biotechnology using Agrobacterium-mediated transformation to improve HFA levels in lesquerella. Knowledge of P. lindheimeri seed development and HFA synthesis is required in implementing a biotech approach. Assessment of the seed development of P. lindheimeri is essential in the selection of seed samples and the construction of libraries for acquiring genes and information needed in Agrobacterium-mediated transformation. Yet, the precise seed development stages in P. lindheimeri have not been established. Here, we describe the time course of the entire seed development and present the changes of seed growth, lipid accumulation and fatty acid (FA) profile along the development. The relationships among these changes are discussed.

Technical Abstract: Hydroxy fatty acids (HFAs) are valuable industrial raw materials used in many industries. Physaria lindheimeri (Pl) accumulates over 80% HFA, in the form of lesquerolic acid (20:1OH), in its seed oil. Understanding the seed development of Pl is an important step to utilizing this unique wild species as a genetic source of HFAs biosynthesis. The changes of seed growth, lipid accumulation and fatty acid composition during seed development of Pl were examined from 14 days after pollination (DAP) to desiccation (56 DAP). The seed development could be divided into three periods. During the early period (14 and 21 DAP), seed rapidly increased in size and fresh weight. In mid-maturation period (28, 35, and 42 DAP), lipids and dry weights accumulated steadily. When seeds developed to late-maturation/desiccation stages (49 and 56 DAP), fresh weight dropped significantly due to water loss, and the dry weight and lipid accumulation reached their maximums. Seed color remained green up to 42 DAP and turned to orange-brown at 49 and 56 DAP. The major fatty acid 20:1OH started accumulation when seeds developed into mid-maturation stage (28 DAP) and the accumulation continued thereafter up to 56 DAP, eventually reaching up to 77% of the total seed oil. The HFA accumulation indicates embryonic storage tissue formation, thus 28 DAP defines a critical time point for seed development entering reserve synthesis and accumulation. The information and knowledge obtained from this study are essential to the success of HFA production using commodity oilseed crops.